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The power of place Joordens, J.C.A.

2011

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citation for published version (APA) Joordens, J. C. A. (2011). The power of place: climate change as driver of hominin evolution and dispersal over the past five million years.

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Download date: 23. Sep. 2021 VRIJE UNIVERSITEIT

The power of place: climate change as driver of hominin evolution and dispersal over the past five million years

ACADEMISCH PROEFSCHRIFT

ter verkrijging van de graad Doctor aan de Vrije Universiteit Amsterdam, op gezag van de rector magnificus prof.dr. L.M. Bouter, in het openbaar te verdedigen ten overstaan van de promotiecommissie van de faculteit der Aard- en Levenswetenschappen op donderdag 31 maart 2011 om 15.45 uur in de aula van de universiteit, De Boelelaan 1105

door

Josephine Caroline Antoinette Joordens

geboren te Venlo promotor: prof.dr. D. Kroon copromotor: dr. H.B. Vonhof Leescommissie: prof. dr. G.J. Boekschoten dr. C.S. Feibel prof. dr. M.G. Leakey prof. dr. J.W.M. Roebroeks prof. dr. F. Spoor dr. J. de Vos

Paranimfen:

Jeroen van der Lubbe Jeroen van Wetten

voor Marc Joordens en Mariet Joordens-Wolters Lay-out: Anne Schulp Cover design: Jan Willem Dogger

Front cover: Flamingoes over Lake Turkana (photo Anne Schulp)

Inset images reflect the inland-coastal suc- cession of forest types in the Arabuko-Sokoke coastal forest, Kenya (photos author). Top: Brachystegia woodland Middle: strangler fig in mixed forest Bottom: mangrove with oysters

Back cover: Sample bags with paleolake sediments (photo Anne Schulp) Contents

Introduction and summary 9

Inleiding en samenvatting 17

1. Relevance of aquatic environments for homi- nins: a case study from Trinil (Java, Indonesia) 23

2. Climatic and environmental reconstructions in the Turkana Basin: how useful are oxygen isotope ratios? 49

3. 87Sr/86Sr as a novel climate proxy recording precessional cycles in the hominin-bearing Turkana Basin 65

4. The power of place: hominin evolution and dispersal driven by climate change between ~ 5 – 2.5 Ma 91

Epilogue: the evolutionary and societal relevance of aquatic resource use by hominins 117

Dankwoord / Acknowledgements 123

5

Introduction and summary

What is the origin and history of our species? sion (“the power of place”) needs to be taken into Darwin (1871) first addressed this fundamental account, since the geography of Africa is very question in his book “The Descent of Man”. He diverse. Locally different climatic and environ- claimed that humans are most closely related to mental conditions will have exerted locally dif- the African great apes (chimpanzees and goril- ferent influences on hominin evolution and dis- las) and hence that the origin of humankind must persal. So far, the impact of the spatial dimension lie in Africa. Since then, his prediction has been has hardly been explored in climate-evolution borne out by the discovery of at least 16 differ- studies. Thirdly, to establish causal relationships ent hominin species (preceding modern Homo between climatic and evolutionary events, it is sapiens) fossilized in African deposits over the crucial to identify testable ecological and physi- past ~ 7 million years. Hominins are defined as ological mechanisms for transmitting climatic members of the taxon (“tribe”) Hominini, which cause to evolutionary effect. comprises modern humans and their extinct rel- atives over the past ~ 7 million years: all species Objectives of the genera Homo, Australopithecus, Paranthropus, Kenyanthropus, Ardipithecus, Orrorin and Sahelan- The ultimate aim of this study is to elucidate thropus. Where, when and why did these species the influence of climate and environmental arise? Climatic and environmental changes are change on African hominin evolution and dis- strong drivers of evolution, and it is assumed that persal over the past ~ 5 million years. To achieve these processes played a major role in hominin this, I focused on meeting the three challenges evolution and dispersal. Many hypotheses have mentioned above: reconstruction of a regional been put forward to link climate and environ- paleoclimate record as well as improvement of mental change with important junctions in the age control of hominin fossil occurrences, rec- evolution of the human lineage (e.g. deMenocal ognition of the importance of geography, and 2004; Fig.1). However, in order to test these hy- identification of testable biological mechanisms potheses (or to generate new ones) three impor- that link climate and environmental change to tant requirements should be met (Behrensmeyer, evolution of hominin populations. An important 2006). underlying assumption, stemming in part from my background as a freshwater and marine ecol- Firstly, high-resolution temporal synchronic- ogist, is that the presence of water always must ity of climatic and evolutionary events needs to have been an important factor for hominins: as be demonstrated before any causal relationship drinking water, but possibly also as a source of between the two events can be considered. The freshwater and marine food resources. problem is that especially in continental settings where hominin fossils are found, regional climate Study sites records resolving change at the appropriate evo- lutionary timescales (5-30 thousand years (ky)) The fieldwork for this study was carried out in are generally very scarce or not available. Also, 2004, 2006 and 2010, in ~ 2 million year old lake age control on hominin fossil occurrences is not sediments along the eastern shore of Lake Tur- sufficiently tight. Secondly, the spatial dimen- kana (Kenya, Ethiopia), formerly named Lake 7 Age African Climate Hominid Evolution East African ∂18O (Ma) Variability Soil carb. ∂13C 0 -4 -8 -12 Glacial Interglacial 0 H. erectus

100 kyr 100 kyr H. sapiens

1 P. robustus P. boisei P. ? H. habilis

Acheulean Homo rudolfensis Paranthropus aethiopicus 2 41 kyr 41 kyr Au. africanus

? Au. garhi Oldowan ?

? Au. afarensis 3 ?

Kenyanthropus ? platyops Au. bahrelghazali 23-19 kyr

4 Australopithecus anamensis

Ardipithecus ramidus

Grassland Woodland (deMenocal, 1995) (After White et al., 1999; Lieberman, 2001) (Cerling and Hay, 1988; (Shackleton et al., 1990; Cerling, 1992; Wynn, 2000) Mix et al., 1995)

Figure 1. Summary diagram of important paleoclimatic and hominin evolution events over the past 4.5 Ma (deMenocal, 2004). Important junctions in hominin evolution, such as the emergence of Homo erectus at ~ 1.8 Ma, have been linked to contemporaneous paleoclimatic events (deMenocal, 2004).

Rudolf (Fig. 2). It has been -and still is- a privi- (Gibbons, 2006). Since the start of the Koobi Fora lege to work in this remote and harshly beauti- Research Project in 1968, hundreds of hominin ful area inhabited by the Dasanetch, Turkana and other animal and plant fossils have been and Gabbra. Made known to the outside world and continue to be found (Fig. 4, 5). The research as recently as 1888 by the explorers Teleki and presented in this thesis contributes to providing Von Höhnel (Brown, 1989), Lake Turkana earned a climatic, environmental and ecological context the status as an iconic geographic space in East for these important fossils from the “cradle of Africa. The vast lake in the windswept desert at- mankind” in the Turkana Basin. tracted adventurers for many reasons (e.g. ivory, or crocodiles; Graham and Beard, 1973) but also The other important site featuring in this thesis just because it was there: reaching this place was is Trinil in the Solo Basin on Java (Indonesia). In a moving experience (Fig. 3). It enabled individu- 1893, on the banks of the Solo River, the Dutch als to challenge and define themselves, to test anatomist Eugène Dubois discovered fossils of their stamina and skills, and to earn distinction a transitional form between ape and human: (Brown, 1989; Imperato, 2006). In the 1960’s the Pithecanthropus erectus or Homo erectus as it is iconic status of Lake Turkana was strengthened now called (Dubois, 1894; Fig. 6). Dubois (Fig. 7) by the discovery of rich fossil hominin-bearing was the first scientist who combined biological, beds on its eastern shore, at Koobi Fora. Paleo- paleontological and biogeographical informa- anthropologist and fossil hunter Richard Leakey tion to predict the possible geographic location had noticed these deposits by looking out of the where such transitional fossils could be pres- window of a small airplane, when he was flying ent. In 1887 he gave up his promising university back from Ethiopia on a detour to avoid a storm career in Amsterdam to actually go and look for 8 0 20 40 60 36°E 37°E Kilometers Nile K.S.A. Red Sea

Blue Nile ERITREA YEMEN

Kibish Lower SUDAN ETHIOPIA Omo Valley Gulf of Aden DJIBOUTI

Addis Ababa 5°N Shungura SOMALIA

W hit e Nile Omo R. Omo

Todenyang UGANDA A KENYA Indian Ocean Ileret Nariokotome llia Omo R Il A

. ETHIOPIA 4°N Kangaki Lomekwi Koobi Fora Region Turkana iet Il L KENYA taboi okochot Il Er Region a Lake Turkana 41 K Ileret or B Kalakol Tulu 10 Laga 4o 15’ N 129 130

131 idge Lodwar Turkwel R. i R Gus 118 ar 105 ar 3°N K

o 115 Lowa- 4 N sera 104 idge a R Loiyan- 102 100 or galani Lake Turkana Koobi F 123 Bura Hasuma

io R. o Ker 3 45’ N Il L okochot

Suguta B Depression C 0 5 10 15 20km

Figure 2. A: Location of Lake Turkana in NE Africa. B: Present-day Lake Turkana with Pliocene and Pleistocene depos- its indicated in grey. C: Overview of the numbered paleontological collecting areas on the NE coast of Lake Turkana. those fossils. He went to the Dutch East Indies to could only be understood in the context of their search for the proverbial needle in the haystack, environment. Therefore Dubois collected all fos- and amazingly by 1893 he had found it (Shipman, sil plant and animal remains from the 2001; Theunissen, 1989). The other remarkable “Pithecanthropus” excavation site, not only the thing about Dubois is that he was a true ecologist: spectacular mammalian bones but also tiny bird he realized that his man-ape/ape-man fossils and fish bones, as well as large amounts of mol- 9 Figure 3. First view on Lake Turkana after a three days’ drive from Nairobi.

luscan shells. Since its arrival in the Netherlands to understanding hominin evolution, since diet early in the 20th century the rich Dubois Collec- influences body proportions, brain size, cogni- tion has been meticulously curated, presently at tion, and habitat preference. Here we provide the Netherlands Centre for Biodiversity Naturalis ecological context for the current debate on in Leiden (The Netherlands). I was –and am– modernity (or not) of aquatic resource exploita- granted the opportunity to work in this unique tion by hominins. We use the Homo erectus site collection. Presently, the Trinil site is no longer of Trinil (Solo Basin on Java, Indonesia) as a case accessible due to permanently high river water study to investigate how research questions on levels. Thanks to Dubois’ foresight, it is still pos- possible dietary relevance of aquatic environ- sible to reconstruct the ecological context of ments can be addressed. Faunal and geochemical Javanese Homo erectus, and derive new hypoth- (strontium isotope) analyses of aquatic fossils eses on its resource use. from the Trinil Hauptknochenschicht (HK) fauna demonstrate that Trinil at ~1.5 million years ago Results and conclusions (Ma) contained near-coastal rivers, lakes, swamp forests, lagoons, and marshes with minor marine Chapter 1 – In this chapter we explore the possible influence, laterally grading into grasslands. Trinil relevance of aquatic environments (lakes, rivers, HK environments yielded at least eleven edible seashores) as sources of aquatic food items for mollusc species and four edible fish species that hominins. Knowledge about dietary niche is key could be procured with no or minimal technol- 10 Figure 4. Fossil skull KNM-ER 1470, attribut- ed to Homo rudolfensis. This fossil was found by Bernard Ngeneo in 1972 (Leakey, 1973).

ogy. We demonstrate that, from an ecological Turkana Basin allows distinction between lake, point of view, the default assumption should be delta (river plume) and river paleoenvironments. that omnivorous hominins in coastal habitats The presence of large healthy fossil bivalve shells with catchable aquatic fauna could and would in the paleolake sediments indicates that alkalin- have consumed aquatic resources. The hypoth- ity in the Turkana Basin at ~2 Ma must have been esis of aquatic exploitation can be tested with lower than today, despite the concomitant lacus- taphonomic analysis of aquatic fossils associated trine δ18O values of ~ +6 ‰ that are similar those with hominin fossils. We show that midden-like in the present-day highly alkaline Lake Turkana. characteristics of large bivalve shell assemblages This can be explained by the non-linear response containing Pseudodon and Elongaria from Trinil of lake water δ18O to increasing evaporation HK indicate deliberate collection by a selective (Craig-Gordon model). Environmental conditions agent, possibly hominin. The important message in the paleolake at ~ 2 Ma were more favorable resulting from this chapter is that the burden of than those in modern Lake Turkana: it provided proof has been shifted: instead of having to pro- good drinking water and abundant aquatic mol- vide evidence of aquatic exploitation before it is luscs, fish and other aquatic animals (crocodile, regarded as a realistic option, evidence is needed turtle) as a possible hominin food supply. when pleading that hominins in coastal habitats could or would not exploit aquatic resources. Chapter 3 – In this chapter we study the influ- ence of orbital paleoclimate cycles on hominin Chapter 2 – In this chapter we test whether oxy- evolution, which is a key challenge in paleoan- gen isotope ratios (δ18O) of fossil bivalve shells thropology. The two major unresolved issues from ~2 million year old hominin-bearing sedi- are: the unavailability of a climate proxy yield- ments in the Turkana Basin can be used to recon- ing high-resolution (< 20 kyr) terrestrial climate struct climate and environments in this region. records, and the lack of age control on hominin We show that seasonal shifts in δ18O values re- fossil occurrences at sufficiently high resolu- corded by modern and fossil shells from the Tur- tion. In the previous chapter we have shown that kana Basin are caused predominantly by wet-dry oxygen isotope ratios of fossil lacustrine shells of seasonal changes in host water chemistry, forced the Turkana Basin cannot be used to reconstruct by summer monsoonal rainfall over the Ethiopian paleoclimate. In this chapter we therefore de- Highlands. Due to strong evaporation and damp- velop and apply a novel climate proxy, strontium ening of the seasonal δ18O signal in lakes, fossil isotope ratios (87Sr/86Sr) of lacustrine fish fossils shells from lake sediments are not suitable for from the Turkana Basin, that captures orbitally reconstruction of paleoclimate and paleoseason- forced variation in summer monsoon intensity ality. In contrast, fossil shells from delta or river over the Ethiopian Highlands. We successfully facies can be used for this purpose. The combina- applied the climate proxy to a ~ 150 kyr time in- tion of δ18O and δ13C data from fossil shells in the terval of ~2 million year old paleolake deposits 11 12 containing hominin fossils. Existing age control the most important influence on hominin evolu- of the studied interval was improved by a new tion by causing contraction of the Indian Ocean magnetostratigraphic record precisely locating coastal forest towards the equator. We argue that the base of the Olduvai chron near the bottom this ecological mechanism of habitat fragmenta- of the sequence. Spectral analysis demonstrates tion caused a tripartite separation of Australo- that 87Sr/86Sr variability is primarily determined pithecus afarensis populations living along the by precession, which enables us to place hominin Indian Ocean coast. As a consequence, the three fossils in an astronomically-tuned climate frame- geographically isolated populations subsisted in work. The Sr climate proxy is potentially appli- different environmental conditions, which led to cable to all hominin-bearing lake deposits in the a cladogenetic split in the hominin lineage. Fi- Turkana Basin, ranging in age from ~ 4.2 to 0.8 nally, we show how the aridity refuge model can Ma. Our results show that between ~ 2 and 1.85 be used to predict testable patterns in the fossil Ma the Turkana Basin remained well-watered record of other mammals, and to predict the lo- and inhabited by hominins even during periods cations of suitable new fossil hunting areas. of precession maxima when summer monsoon intensity was lowest. This is in contrast to other Chapter 5 – This chapter comes full circle by as- basins in the East African Rift System (EARS) sessing the evolutionary and societal relevance that were impacted heavily by precession-forced of aquatic resource use by hominins. In contrast droughts. We hypothesize that during lake phas- to terrestrial foods, aquatic food sources are es, the Turkana Basin was an aridity refugium for rich in substances that have a strong impact on permanent-water dependent fauna –including physiology, gene expression, brain growth and hominins- over the precessional climate cycles. development. The most important one is DHA (docosahexaenoic acid), an essential fatty acid Chapter 4 – In this chapter we postulate and de- synthesized by phytoplankton and progressively velop a new model, the aridity refuge model, to bio-accumulated by aquatic organisms higher up clarify the influence of climate change on hom- in the food chain. Hence, continuous consump- inin evolution and dispersal in Africa between ~ tion of aquatic food sources over milions of years 5 and 2.5 Ma. The model holds that the longitudi- constitutes a direct and powerful physiological nal Indian Ocean coastal forest strip provided an mechanism influencing the evolution of the hu- isolated aridity refugium, conducive to evolution, man lineage. Therefore, despite the difficulties in during recurrent long-periodic (~ 400 ky) dry interpreting subtle clues for aquatic resource use, episodes over the past millions of years. From it is worth the effort to establish the antiquity of this refuge, evolved species could disperse far earliest aquatic resource use by hominins, and inland to rift basins via (re-)established fluvial assess the relative contribution of aquatic versus corridors, whenever onset of long-periodic hu- terrestrial food resources in the hominin diet. mid episodes in eastern Africa allowed expansion This is also important from a societal perspective from the coastal enclave. We develop the model since DHA appears to play a major role in modern by: 1) setting up the climatic-tectonic framework, human health and development. DHA deficiency 2) choosing age, geographic location and genus is implicated in diseases and problems (e.g. of the “stem hominin” in the model, and 3) defin- coronary heart disease, inflammatory diseases, ing the algorithm that makes the model “run” to depression, aggression and antisocial behaviour produce predictions on evolution and dispersal. –even homicide-, and impaired visual and neu- These predictions are validated with data from rological development of children) that have a the available fossil record. We conclude that pat- high prevalence in modern societies and cause terns in fossil occurrence of hominin species major human suffering and economic costs. If the between ~ 5 and 3 Ma can be fully explained by increasingly recognized modern human need for invoking long-periodic (~ 400 ky) wet-dry cli- preformed DHA in the diet can be placed in an mate changes as postulated in the aridity refuge evolutionary context, crucial recommendations model. We hypothesize that after ~ 3 Ma, the for dietary change will carry more weight and so- Northern Hemisphere Glaciation (NHG) exerted ciety will benefit. I argue that this dietary change

Figure 5 (left). Typical exposures of fossil-bearing paleolake deposits in Area 102, Koobi Fora. Persons (Hubert Vonhof (right) and the author) indicate the scale. 13 Figure 6 (above). Fossil skull cap, femur and molar of the holotype of Homo erectus, excavated from Trinil (Dubois, 1894).

Figure 7 (right). Eugène Dubois in Amsterdam, 1883.

should ideally consist of deriving our essential long-chain polyunsaturated fatty acids (e.g. DHA) directly from cultured phytoplankton, the green base of the aquatic food chain.

References

Behrensmeyer, A.K., 2006. Climate change and Gibbons, A., 2006. The First Human: the Race to human evolution. Science 311 (5760): 476-478. Discover our Earliest Ancestors. Anchor Books, Brown, M., 1989. Where Giants Trod: the Saga of Random House New York. Kenya’s Desert Lake. Quiller Press, London. Imperato, P.J., 2006. Lake Rudolf as an iconic geo- Darwin, C., 1871. The Descent of Man, and Selec- graphic space in East Africa. Ethnohistory 53 tion in Relation to Sex. John Murray, London. (1): 13-33. deMenocal, P.B., 2004. African climate change and Leakey, R.E.F., 1973. Evidence for an advanced faunal evolution during the Pliocene-Pleisto- Plio-Pleistocene hominid from East Rudolf, cene. Earth and Planetary Science Letters 220 Kenya. Nature 242: 447-450. (1-2): 3-24. Shipman, P., 2001. The Man who Found the Miss- Dubois, E.,1894. Pithecanthropus erectus. Eine ing Link: Eugène Dubois and his Lifelong Quest Menschenähnliche Übergangsform aus Java. to Prove Darwin Right. Simon & Schuster. Landsdrukkerij, Batavia. Theunissen, B., 1989. Eugène Dubois and the Ape- Graham, A., Beard, P., 1973. Eyelids of Morning: man from Java. Kluwer Academic Publishers, the Mingled Destinies of Crocodiles and Men. Dordrecht. Chronicle Books, San Francisco. 14 Inleiding en samenvatting

(voor figuren en referenties, zie de Engelstalige introductie)

Wat is de oorsprong en historie van onze soort? gehad op menselijke evolutie en verspreiding. Darwin (1871) behandelde als eerste deze funda- Tot dusverre is de invloed van deze ruimtelijke mentele vraag in zijn boek “The Descent of Man”. dimensie nauwelijks onderzocht in studies naar Hij stelde dat mensen het nauwst verwant zijn klimaat en menselijke evolutie. Ten derde is het aan de Afrikaanse mensapen (chimpansees en van belang om toetsbare ecologische mechanis- gorilla’s) en dat daarom de oorsprong van onze men, waardoor klimaatverandering daadwerke- soort in Afrika moest liggen. Sindsdien is zijn lijk kan leiden tot evolutionaire verandering, te stelling onderbouwd door de vondst van fossiele identificeren. resten van tenminste 16 mensachtige (hominide) soorten (voorlopers van de moderne Homo Doel van het onderzoek sapiens) in Afrikaanse afzettingen over de laatste ~ 7 miljoen jaar. Waar, wanneer en hoe ontston- Het uiteindelijke doel van dit onderzoek is om te den deze soorten? Veranderingen in klimaat en verhelderen hoe klimaat en omgeving invloed omgeving beïnvloeden evolutie in hoge mate, en hebben gehad op de evolutie en verspreiding van aangenomen wordt dat deze processen een bepa- Afrikaanse hominiden over de afgelopen ~5 mil- lende rol hebben gespeeld in menselijke evolutie joen jaar. Om dit te bereiken heb ik het volgende en verspreiding. Vele hypotheses zijn geformu- gedaan: 1) reconstructie van lokale paleokli- leerd om verband te leggen tussen klimaatveran- maatsgegevens en verfijning van de ouderdoms- deringen en splitsingen in de menselijke afstam- bepaling van hominide fossielen, 2) aantonen hoe ming (bv. deMenocal 2004; Fig. 1). Om deze hy- geografische locatie bepalend is voor evolutie en potheses te testen (of om nieuwe te formuleren) verspreiding, en 3) aanwijzen van ecologische moet aan drie belangrijke voorwaarden worden mechanismen die het verband vormen tussen voldaan (Behrensmeyer, 2006). veranderingen in klimaat en omgeving en evo- lutie van hominiden. Een belangrijke onderlig- Ten eerste moet worden aangetoond dat kli- gende aanname, deels afkomstig uit mijn achter- matologische en evolutionaire gebeurtenissen grond als marien bioloog, is dat de aanwezigheid precies gelijktijdig hebben plaats gevonden, alvo- van water altijd een belangrijke factor moet zijn rens enig causaal verband ertussen kan worden geweest voor hominiden: als drinkwater maar overwogen. Het probleem is dat, met name voor ook als mogelijke bron van voedsel uit zoet water de gebieden waar mensachtige fossielen gevon- of uit zee. den zijn, er geen gegevens beschikbaar zijn die klimaatverandering op de correcte tijdschaal Onderzoeksgebied (ordegrootte 5-30 duizend jaar) laten zien. Ook is de ouderdom van mensachtige fossielen onvol- Het veldwerk voor dit onderzoek is uitgevoerd in doende nauwkeurig te bepalen. Ten tweede moet 2004, 2006 en 2010 in ~2 miljoen jaar oude meer- de ruimtelijke dimensie (“the power of place” afzettingen langs de oostkust van Lake Turkana – de invloed van de locatie) beschouwd worden (Kenia, Ethiopië) voorheen Lake Rudolf geheten omdat de geografie van Afrika bijzonder divers is. (Fig. 2). Het was – en is – een voorrecht te mogen Lokale verschillen tussen klimatologische en om- werken in dit afgelegen en woest mooie gebied, gevingsomstandigheden zullen invloed hebben dat bewoond wordt door de Dasanetch, de Tur- 15 kana en de Gabbra. Lake Turkana werd pas in “Pithecanthropus” opgravingsplaats. Niet alleen de 1888 voor het eerst aan de buitenwereld gepre- spectaculaire botten van grote zoogdieren maar senteerd door de ontdekkingsreizigers Teleki en ook de kleinste vis- en vogelbotjes, alsmede vele von Höhnel (Brown, 1989) en kreeg een iconische schelpen. Sinds de aankomst van deze materialen geografische status in Oost Afrika. Het immens in Nederland aan het begin van de vorige eeuw is grote meer in de winderige woestijn trok avon- de rijke Dubois collectie nauwkeurig beschreven turiers om vele redenen (zoals ivoor, en kroko- en opgeborgen, momenteel in het Nederlands dillen; Graham & Beard, 1973), maar ook louter Centrum voor Biodiversiteit Naturalis in Leiden omdat het daar lag: het bereiken van deze plek (Nederland). Ik had – en heb – het voorrecht om was een emotionele ervaring (Fig. 3). Het stelde te werken in deze unieke historische collectie. mensen in staat om zichzelf te bewijzen, hun uit- Dankzij Dubois’ inspanningen van meer dan 100 houdingsvermogen en talenten te testen en om jaar geleden is het mogelijk om de aquatische zich te onderscheiden (Brown, 1989; Imperator, omgeving van Homo erectus in detail te reconstru- 2006). In de zestiger jaren van de vorige eeuw eren, en om nieuwe hypothesen te formuleren werd de iconische status versterkt door de vondst omtrent diens gebruik van voedselbronnen. van afzettingen met hominide fossielen aan de oostkust van het meer, bij Koobi Fora. Deze afzet- Resultaten en conclusies tingen waren ontdekt door paleoantropoloog en fossielenjager Richard Leakey toen hij, onderweg Hoofdstuk 1 – In dit hoofdstuk onderzoeken we het vanuit Ethiopië en uitwijkend voor een storm, uit mogelijke belang van aquatische systemen het raam van zijn vliegtuigje naar beneden keek (meren, rivieren, kustgebieden) als bron van (Gibbons, 2006). Sinds het begin van het Koobi voedsel voor hominiden. Kennis over de voedsel- Fora Research Project in 1968 zijn en worden niche is de sleutel tot het begrip van menselijke honderden fossielen van hominiden, maar ook evolutie, omdat dieet invloed heeft op lichame- van andere flora en fauna gevonden (Fig. 4, 5). lijke proporties, hersenomvang, cognitie en voor- Dit proefschrift draagt bij aan inzicht in de kli- keur voor leefomgeving. Hier schetsen we de eco- matologische en ecologische context voor deze logische context voor het huidige debat over de belangrijke fossielen uit “de wieg der mensheid” moderniteit (of niet) van het eten van aquatisch in het Turkana Bekken. voedsel door hominiden. We gebruiken de vind- plaats van Homo erectus in Trinil (Solo Bekken op De andere bepalende plek voor mijn onderzoek is Java, Indonesië) als voorbeeld om na te gaan hoe Trinil in het Solo Bekken op Java (Indonesië). In onderzoeksvragen over mogelijke relevantie van 1893, aan de oevers van de Solo rivier, ontdekte aquatische voedselbronnen kunnen worden be- Eugène Dubois fossielen van een overgangs- antwoord. Faunale en geochemische (strontium vorm tussen aap en mens: Pithecanthropus erectus isotopen) analyse van aquatische fossielen van of Homo erectus zoals deze nu wordt genoemd de Trinil Hauptknochenschicht (HK) fauna tonen (Dubois, 1894; Fig. 6). Dubois (Fig. 7) was de eerste aan dat het gebied rond Trinil bestond uit laag- wetenschapper die biologische, paleontologische landrivieren, meren, moerasbossen en lagunes en biogeografische informatie gebruikte om de met enige mariene invloed, die geleidelijk over- mogelijke geografische locatie van dergelijke gingen in graslanden. De omgeving van Trinil overgangsfossielen te voorspellen. In 1887 gaf hij HK leverde tenminste elf eetbare soorten schelp- zijn veelbelovende wetenschappelijke carrière in dieren en vier eetbare vissoorten, die konden Amsterdam op om deze fossielen ook daadwer- worden gevangen met minimale technologische kelijk te gaan ontdekken. Hij vertrok naar Ne- hulpmiddelen. We tonen aan dat vanuit ecolo- derlands Oost-Indië op zoek naar een naald in de gisch gezichtspunt de basisaanname zou moeten hooiberg, en wonder boven wonder vond hij die zijn dat hominiden die leefden in kustgebieden, (Shipman, 2001; Theunissen, 1989). Het andere met eenvoudig te vangen aquatische fauna, opmerkelijke aan Dubois is dat hij een echte eco- deze voedselbronnen kunnen en zullen hebben loog was, en zijn tijd ver vooruit. Hij realiseerde gebruikt. De hypothese van aquatisch voedsel- zich dat mens-aap/aap-mens fossielen alleen gebruik kan worden getoetst met tafonomische konden worden begrepen in de context van hun analyse van aquatische fossielen die geassocieerd leefomgeving. Dubois verzamelde daarom alle zijn met hominide fossielen. We laten zien dat plantaardige en dierlijke fossielen uit de kenmerken van schelp-assemblages uit Trinil HK, 16 die de eetbare soorten Pseudodon en Elongaria be- konden worden door de daar levende hominiden. vatten, wijzen op verzameling van deze schelpen voor consumptie –mogelijk door Homo erectus. De Hoofdstuk 3 — In dit hoofdstuk bestuderen we de belangrijke boodschap van dit hoofdstuk is dat de invloed van orbitale klimaatcycli op menselijke bewijslast nu is omgekeerd. In plaats van aquati- evolutie in oostelijk Afrika. Het gaat dan om kli- sche exploitatie te moeten bewijzen voordat dit maatveranderingen op lange tijdschalen van on- kan worden geaccepteerd als realistische optie, is geveer 20, 40, 100 en 400 duizend jaar, die worden het nodig om bewijs te leveren als men staande veroorzaakt door cyclische variaties in bewegin- wil houden dat hominiden die in de kustzone gen van de Aarde. Twee tot dusver onopgeloste leefden, géén aquatische voedselbronnen konden kwesties bij dit soort onderzoek zijn het gebrek of wilden exploiteren. aan gedetailleerde lokale klimaatgegevens, en de onvoldoende nauwkeurige datering van de afzet- Hoofdstuk 2 – In dit hoofdstuk testen we of zuur- tingen waar hominide fossielen uit komen. In stofisotopen ratios (δ18O) van fossiele tweeklep- het vorige hoofdstuk hebben we aangetoond dat pige schelpen uit ~2 miljoen jaar oude meerafzet- zuurstofisotopen ratios van fossiele meerschel- tingen in het Turkana Bekken kunnen worden pen uit het Turkana Bekken niet kunnen worden gebruikt om een reconstructie te maken van gebruikt voor reconstructie van het paleoklimaat. klimaat en omgeving in dit gebied. We laten zien In dit hoofdstuk ontwikkelen we daarom een dat variatie in δ18O waarden, zoals vastgelegd in nieuwe klimaat-“proxy”, de strontiumisotopen groeilijnen van moderne en fossiele schelpen uit ratio (87Sr/86Sr) van visfossielen uit oude meerfa- het Turkana Bekken, voornamelijk wordt veroor- ses in het Turkana Bekken. Door de tijd heen is in zaakt door nat-droog seizoensgebonden veran- fossiele vissenbotjes en –tanden (die Sr bevatten) deringen in de chemische samenstelling van het de orbitaal beïnvloede variatie in moesson in- meerwater. Op korte tijdschaal van maanden- tensiteit boven de Ethiopische Hooglanden vast- jaren wordt die samenstelling, via de Omo rivier gelegd. De Sr klimaatproxy kan worden gebruikt vanuit Ethiopië, bepaald door seizoenale variatie in alle meerafzettingen in het Turkana Bekken, in regenval boven de Ethiopische Hooglanden. uiteenlopend in ouderdom van ~4.2 tot 0.8 Ma. We tonen aan dat, door sterke verdamping en Wij pasten deze methode toe op een tijdsinterval demping van het seizoenale δ18O signaal in van ongeveer 150.000 jaar, in ~2 miljoen jaar oude meren, fossiele schelpen uit de meerafzettingen meerafzettingen die hominide fossielen bevatten. van het Turkana Bekken niet bruikbaar zijn voor Datering van de afzettingen is verbeterd door reconstructie van het paleoklimaat. Echter, schel- nieuwe magnetostratigrafische metingen, die een pen uit rivierafzettingen kunnen daarvoor wel nauwkeurig gedateerde ompoling van het aard- worden gebruikt. De combinatie van δ18O en δ13C magnetisch veld aan het begin van het tijdsinter- (koolstofisotopen ratios) data van fossiele schel- val lokaliseren. Spectraal-analyse laat zien dat de pen uit het Turkana Bekken maakt het mogelijk 87Sr/86Sr variabiliteit voornamelijk wordt bepaald om verschillende paleo-omgevingen te onder- door de precessie (20 duizend jaar cyclus) van de scheiden: meer, rivierdelta of –pluim, en rivier. Aarde, hetgeen ons vervolgens in staat stelt om De rijke aanwezigheid van grote fossiele schelpen hominide fossielen in een nauwkeurig astrono- in de ~2 miljoen jaar oude meerafzettingen wijst misch gedateerd klimaatsraamwerk te plaatsen. erop dat de zuurgraad destijds lager moet zijn Onze resultaten laten zien dat, door permanente geweest dan tegenwoordig, ondanks de hoge rivierverbinding tussen de Ethiopische Hooglan- δ18O waarden die hetzelfde zijn als de waarden in den en het Turkana Bekken, het meer tijdens het het huidige zeer alkalische Turkanameer -waar hele studie-interval doorlopend van water werd schelpen vrijwel niet kunnen voorkomen. Dit kan voorzien -zelfs gedurende droge perioden tijdens worden verklaard door een niet-lineair verband precessie-maxima als regenval boven Ethiopië op tussen δ18O waarde en toenemende verdamping z’n laagst was. Uit de data blijkt dat het ook door- (Craig-Gordon model). Omgevingscondities in het lopend werd bewoond door hominiden. Dit staat ~2 miljoen jaar oude meer waren gunstiger dan in tegenstelling tot andere bekkens in het Oost die in het hedendaagse Turkanameer: het oude Afrikaanse Rift Systeem, die veel zwaarder wer- meer bevatte goed drinkwater en grote hoeveel- den getroffen door precessie-gerelateerde droog- heden schelpdieren, vis en andere waterdieren teperiodes. Wij stellen dat het oude Turkanameer (zoals krokodillen en schildpadden) die gegeten een oase was, die tijdens precessie-gestuurde 17 droge periodes een refugium (schuilplaats) bood worden toegepast om mogelijke nieuwe locaties aan hominiden. Zij konden in het Turkana Bek- in Afrika te identificeren waar fossiele hominiden ken wel, maar elders in de Oost-Afrkaanse Rift gezocht kunnen worden. niet, de door precessie veroorzaakte droogte pe- riodes overleven. Hoofdstuk 5 – Dit hoofdstuk maakt de cirkel rond, door de evolutionaire en maatschappelijke re- Hoofdstuk 4 – In dit hoofdstuk postuleren we levantie van het gebruik van aquatisch voedsel het “droogte-refugium model”. Dit model stelt door hominiden nader te beschouwen. In tegen- dat de het bos langs de Indische Oceaan kust in stelling tot terrestrisch voedsel is watervoedsel oostelijk Afrika een geïsoleerd droogterefugium rijk aan stoffen die een sterke invloed hebben op bood, gunstig voor evolutie gedurende cyclisch fysiologie, gen-expressie, hersengroei en ontwik- voorkomende (ongeveer elke 400 duizend jaar) keling. De belangrijkste stof is DHA aride episodes gedurende de afgelopen miljoenen (docosahexaenoic acid), een essentieel omega-3 jaren. De in dit refugium geëvolueerde soorten vetzuur dat wordt gevormd door fytoplankton konden zich ver landinwaarts in Afrika versprei- (eencellige algen), en opgehoopt door aquatische den langs door rivieroevers gevormde corridors, organismen (bv. schelpdieren en vissen) hogerop steeds wanneer cyclisch voorkomende natte in de voedselketen. Consistente consumptie van episodes expansie mogelijke maakte vanuit de aquatisch voedsel over miljoenen jaren tijd vormt enclaves langs de oostkust. Hier ontwikkelen we aldus een potentieel direct en krachtig ecolo- het droogte refugium model in ruimte en tijd, gisch mechanisme in de menselijke evolutie. Het om de invloed van klimaatsverandering op ho- is daarom de moeite waard om vast te stellen minide evolutie en verspreiding te verklaren in hoe lang hominiden al gebruik maken van deze de periode tussen ~5 en 2.5 Ma. We doen dit door voedselbronnen, en hoe groot het aandeel daar- middel van: 1) het opzetten van een klimaats- en van in hun dieet was. Dit soort onderzoek is ook tektonische raamwerk, 2) het kiezen van leef- van maatschappelijk belang omdat DHA een be- tijd, geografische locatie en genus van de “stam langrijke rol blijkt te spelen in de gezondheid en hominide” in het model en 3) het definiëren van ontwikkeling van de moderne mens. Een tekort het algoritme in het model dat voorspellingen aan DHA wordt gerelateerd aan ziektes en pro- produceert over evolutie en verspreiding. Deze blemen (hart- en vaatziektes, ontstekingsziektes, voorspellingen worden vervolgens gevalideerd ontwikkelingsproblemen van ogen en zenuwstel- met gegevens uit de beschikbare gedateerde fos- sel bij jonge kinderen, depressie, asociaal gedrag, siele afzettingen. We concluderen dat patronen agressie en doodslag) die veel voorkomen in de in het voorkomen van fossiele hominiden tussen moderne samenleving. Deze ziektes en stoornis- ~5 en 3 Ma volledig verklaard kunnen worden sen brengen menselijk lijden en hoge economi- door middel van de regelmatige nat-droog kli- sche kosten met zich. Als de behoefte aan DHA maatscycli (op 400 duizend jaar tijdschaal) vol- in het menselijke dieet kan worden geplaatst in gens het droogte refugium model. Na ~3 Ma had een evolutionaire context, kunnen aanbevelingen de grootschalige ijsvorming op het Noordelijk voor dieetverandering veel meer gewicht in de Halfrond een belangrijke invloed op menselijke schaal leggen en zullen ze mogelijk sneller geac- evolutie, doordat deze een verdroging in Afrika cepteerd worden. Hiervan zal de maatschappij en daarmee inkrimping van het Indische Oceaan profiteren. Men zou kunnen aanbevelen om meer kustbos richting de evenaar veroorzaakte. Wij hy- watervoedsel te gaan eten, maar grootschalige pothetiseren dat dit ecologische mechanisme van visvangst en viskweek brengt weer andere pro- habitat fragmentatie een driedeling veroorzaakte blemen met zich mee. Mijn stelling is daarom dat in hominide populaties die destijds leefden in we de voor ons essentiële vetzuren (zoals DHA) het kustbos langs de Indische Oceaan. Als gevolg het beste rechtstreeks uit gekweekt fytoplankton hiervan bevonden de drie populaties zich geïso- kunnen halen, om deze stoffen vervolgens toe te leerd in verschillende ecologische omstandighe- voegen aan onze voedingsmiddelen. Fytoplank- den, en ondergingen verschillende evolutionaire ton heeft ons mogelijk tot mens gemaakt, en is ontwikkelingen. Het resultaat was een evolutio- nodig om ons menselijk (humaan) te laten blij- naire splitsing in drie nieuwe hominide soorten. ven. Tenslotte laten we zien hoe (in navolging van Eugène Dubois) het droogte refugium model kan 18 1. Relevance of aquatic environments for hominins: a case study from Trinil (Java, Indonesia)

Josephine C.A. Joordens, Frank P. Wesselingh, John de Vos, Hubert B. Vonhof, Dick Kroon Published in: Journal of Human Evolution 57 (6): 656-671 (2009)

Abstract the realized hominin niche. Diet (and dietary change) is widely considered to be an important Knowledge about dietary niche is key to under- factor in hominin evolution (Roebroeks, 2007; standing hominin evolution, since diet influences Ungar, 2007). So far, emphasis has been mainly on body proportions, brain size, cognition and habi- reconstruction of terrestrial, non-aquatic tat preference. In this study we provide ecologi- palaeoenvironments (savannah, woodland, ripar- cal context for the current debate on modernity ian woodland) and on availability of terrestrial (or not) of aquatic resource exploitation by homi- food resources (e.g., Reed, 1997; Wood and Strait, nins. We use the Homo erectus site Trinil as a case 2004; Peters and Vogel, 2005; Copeland, 2007; study to investigate how research questions on Clark and Plug, 2008). Terrestrial paleoenviron- possible dietary relevance of aquatic environ- ments often include lakes, rivers, deltas and ments can be addressed. Faunal and geochemical marshes (e.g., Harris et al, 1987; Feibel et al., 1991; analysis of aquatic fossils from Trinil Hauptkno- Huffman, 2001; Huffman and Zaim, 2003; Wrang- chenschicht (HK) fauna demonstrate that Trinil ham, 2005; Bettis III et al., 2008), which provide at ~1.5 Ma contained near-coastal rivers, lakes, drinking water and potential sources of plant and swamp forests, lagoons and marshes with minor animal foods for hominins. marine influence, laterally grading into grass- lands. Trinil HK environments yielded at least Little is known about the use of aquatic resources 11 edible mollusc species and four edible fish by early hominins (see Erlandson, 2001 for a re- species, that could be procured with no or mini- view). Hominin fossils are often found in associa- mal technology. We demonstrate that, from an tion with aquatic fauna. This can be attributed to ecological point of view, the default assumption the fact that coastal margins of aquatic systems should be that omnivorous hominins in coastal such as lakes, rivers and deltas are taphonomical- habitats with catchable aquatic fauna could have ly favourable for fossilization. Mere association consumed aquatic resources. The hypothesis of fossil hominins and aquatic fauna is in general of aquatic exploitation can be tested with ta- not regarded as an indication for consumption phonomic analysis of aquatic fossils associated of these resources by hominins. Aquatic exploi- with hominin fossils. We show that midden-like tation is only considered as a relevant factor in characteristics of large bivalve shell assemblages hominin evolution when consumption of aquatic containing Pseudodon and Elongaria from Trinil food sources can be proven, as has been done for HK indicate deliberate collection by a selective modern humans: Homo sapiens from coastal South agent, possibly hominin. Africa consumed marine foods at least as early as ~ 164 ± 12 Ka (Marean et al., 2007). Stewart (1994) Introduction has studied patterns of possible fish exploitation in Early Pleistocene sites at Olduvai Gorge where Paleoenvironmental reconstructions of hominin H. habilis and H. erectus fossils were found, making sites provide ecological context for studies of “a strong, although not absolute, case for early hominin evolution. Habitat characteristics, na- hominid fish procurement” (Stewart, 1994, p. ture of predators and competitors, and especially 229). The lack, so far, of proof of aquatic exploita- the availability of food resources all determined tion by early hominins has in practice been inter- 19 preted as evidence for the opposite (e.g. Marean text for the current debate on modernity (or not) et al., 2007). This interpretation has strengthened of aquatic resource exploitation by hominins. A the prevailing assumption that systematic ex- suitable area to study possible dietary relevance ploitation of aquatic resources is modern human of aquatic environments for hominins is the behavior, not present in other hominin species. Solo Basin on Java, Indonesia (Fig. 1) where Homo The recently published evidence of Neanderthals erectus occurred in a coastal environment encom- in Gibraltar exploiting marine resources such as passing lagoonal, riverine and sea coast habitats dolphins, seals, molluscs and fish (Stringer et al., (Huffman, 1999; Huffman et al., 2006). The classi- 2008) has challenged this assumption of moder- cal site Trinil, where the first H. erectus skullcap nity. Shipman (2008) concluded that the coastal and femur were found by Eugène Dubois (1894), Gibraltar sites have yielded excellent evidence is particularly convenient for an investigation of Neanderthal behaviors that are usually cited of aquatic environments. A paleogeographical as hallmarks of modern human behavior: the model of East Java during the Pleistocene (Huff- exploitation of marine resources and seasonality man, 2001; Huffman and Zaim, 2003) indicates or scheduling in the use of resources. If Neander- that Trinil was situated in a riverine environ- thals living in a coastal habitat were capable of ment at ~ 65 km distance from lagoonal lakes doing this, it favours the question: could other of Sangiran, close (~ 15 km) to the sea coast of hominins living in a coastal habitat, such as Homo Randublatung Embayment and at ~100 km from erectus on Java, also have accessed aquatic foods? the Mojokerto Delta (Fig. 2). About 400.000 fos- sils of terrestrial vertebrates, aquatic vertebrates Homo erectus is one of the earliest hominin spe- and aquatic invertebrates have been excavated cies that must have had a considerable amount from Trinil during expeditions by Dubois from of animal protein in its diet, as is evident from 1891-1900 (Dubois, 1907; 1908), by Selenka from the fact that its human-like barrel-shaped tho- 1906-1908 (Selenka and Blanckenhorn, 1911) and rax could not have provided enough room for by other parties (see Van Benthem Jutting, 1937). the typical long plant eater’s gut (Aiello and We use these historical collections to reconstruct Wheeler, 1995). Whether this animal protein was aquatic paleoenvironments at Trinil in the Early completely derived from terrestrial ecosystems Pleistocene, and to establish potential availability or also coming from aquatic fauna -and if so, in of aquatic food resources for Javanese H. erectus. what proportion- is unknown. H. erectus was an Further, we provide an ecological comparison ecological generalist (Wood and Strait, 2004), an with subsistence patterns of other (non-hominin) opportunistic omnivore likely to have exploited terrestrial mammals living in coastal habitats. a broad range of dietary elements ranging from This allows us to discuss probability of aquatic re- plants (fruits, leaves, tubers, seeds) to inverte- source exploitation by hominins, and specifically brates (insects, molluscs) as well as small and by Homo erectus on Java. large vertebrates. In this respect, H. erectus can be compared to omnivorous cercopithecids such Stratigraphy and chronology of the Pleisto- as baboons and macaques (Elton, 2006). Both ba- cene Solo Basin boons and macaques are known to include aquat- ic foods in their diet. For instance, the Chacma The oldest Javanese Homo erectus fossils (e.g., baboon, Papio ursinus, preys on intertidal crabs, Sangiran 27, 4, 31; Indriati and Antón, 2008) limpets, periwinkles, mussels, shrimp, sea lice were found in the coastal deltaic and lacustrine- and shark embryos (Carlton and Hodder, 2003; marshy deposits of the upper Sangiran (or Pucan- Peschak, 2004; Clymer, 2006). The Long-tailed (or gan) Formation (Fig. 3a), as part of the endemic, Crab-eating) macaque, Macaca fascicularis, feeds unbalanced island-type Ci Saat fauna (De Vos, on crabs, shrimp, aquatic molluscs, frogs, octopi 1994; Huffman et al., 2006). This fauna contains and fish (Son, 2003; Malaivijitnond et al., 2007; predominantly species capable of water Stewart, 2008). In a similar way, aquatic organ- crossings, such as cervids, Hexaprotodon, Stegodon isms may have been a potential food source for H. and the felid Panthera. The latter is a relatively erectus, and thus aquatic environments may have strong swimmer that can cover distances of 6 been important parts of the hominin habitat. up to 29 km (Sunquist and Sunquist, 2002). The increasingly abundant presence of Homo erectus The aim of this study is to provide ecological con- continues in the overlying Bapang (or Kabuh) 20 100°E 110°E 120°E

10°N

0°

10°S

Ngandong River Sangiran Solo Mojokerto Trinil Gn. Merapi Gn. Lawu

Figure 1 (left). Map of the Indonesian region with islands Sumatra, Borneo and Java. Inset rectangle: Central Java showing present-day river systems, hominin sites and volcanoes. Gn. = Gunung (volcano). 0 100 km

Formation. The sediments of this formation dicate a more mainland character than the Trinil indicate an environmental change from a lacus- HK Fauna and maximal faunal interchange with trine to an aggrading fluvial system (Larick et the SE Asian mainland (De Vos et al., 1994). The al., 2001). The Trinil Hauptknochenschicht (HK) youngest H. erectus fossils were found in fossil- fauna in the lower part of the Kabuh Formation iferous Solo River terrace deposits at Ngandong contains more species than the Ci Saat fauna, (Oppenoorth, 1936; Antón, 2003). including poor swimmers. This increased species diversity suggests the establishment of a ter- Methods restrial connection between the emerging island of Java and the SE Asian mainland (De Vos et al., For reconstruction of aquatic paleoenvironments 1994). Trinil HK is considered to be contempo- we focus on the Trinil HK fauna in the lower part raneous with the Grenzbank level in the lower of the Kabuh Formation (Fig. 3a, b, c), which also part of the Bapang Formation in the nearby San- comprises the Homo erectus skullcap and femur giran Dome (Soeradi et al. 1985), dated at ca. 1.5 found by Eugène Dubois (1894). We review fossil Ma (Early Pleistocene) (Swisher, 1994; Larick et fish, mollusc, mammal, bird and reptile faunas, al., 2001, Bettis III et al., 2008; Fig. 3a). However, using fossil material and published accounts there is disagreement about the age of Trinil HK: from historical collections curated at Naturalis several other researchers prefer a younger age of National Museum of Natural History (Leiden, The ~ 0.9 Ma for Trinil HK (e.g. Van den Bergh et al, Netherlands). In addition, we perform geochemi- 2001; Antón and Swisher, 2001; Antón, 2003; Bou- cal (strontium isotope) analyses of fish and mol- teaux et al., 2007). In the upper part of the Kabuh lusc fossils in order to study source waters and Formation, fossils of the Kedung Brubus fauna in- salinities of the aquatic habitats. Finally, we as- 21 ?

Volcanic ? highland Java Sea Volcanic apron Vast lowland and/or shallow sea Sandy cal- careous hills Karst hills, Marine channel Rembang Hills many caves stline High karst hills (caves) oa Muddy lowland Karst upland c Low mudstone hills dy rimming ud y coastline sandy calcareous Lmst. (caves) m mudd muddy coastline hills Randublatung Marine Embayment coast Kendeng Hills mu Volcanic hills sandy line dd muddy coastline y coastline Mojokerto Delta Madura Volcanic Sangiran Trinil highland Perning Kedungbrubus Straits m u dd LAWU y co as Lake/ Fluvial Plain tl Volcanic WILIS ine Lagoon highland Volcanic and ARJUNO highland Volcanic Aprons Volcanic highland BUTAK Low karst So SEMERU hills uthern M san Rugged Old-Andesite ou dy c nt oas uplands ains tline Old-Andesite Low karst hills uplands rocky Indian Ocean coastline sandy coastline

Plio-Pleistocene hominin beds Potential coastline habitats Key hominin sites Modern coastline 0 30 60 km Major rivers (hypothetical)

Figure 2. Paleogeographic model of Pleistocene Central Java (from Huffman and Zaim, 2003; adapted from Huffman et al., 2000). The geological reasoning behind this model is addressed in Huffman (2001). The model illustrates the close proximity of diverse long-standing paleogeographic features of the eastern Javan landscape during the period of Homo erectus habitation. It is diagrammatic, not intended to show paleogeography at any specific moment in time. sess availability of potential aquatic food sources, fragments. The Trinil site presently cannot be ex- based on aquatic faunal inventories. Working cavated because of permanent high water levels with historial collections has a drawback. Al- of the Solo river. Thus, the rich historical collec- though all material derives from Trinil HK layers tions from Trinil are the best source of paleoenvi- as presented in Figure 3b and 3c (Dubois, 1907, ronmental information we can access. 1908; Selenka and Blanckenhorn, 1911; Van Ben- them Jutting, 1937), exact stratigraphical prov- Faunal analysis – Fish fossils have been collected enance within this sequence is not always pro- from Trinil during excavations by Dubois and by vided by the excavators. As a consequence, pa- Selenka (Dubois, 1907, 1908; Selenka and Blanck- leoenvironmental reconstructions are relatively enhorn, 1911). The composition of the fossil fish general in character and not as detailed as could assemblage at Trinil is based on our study of be achieved when fossils were collected from the fish fossils in the Dubois collection, and on excavations with a specific reconstruction pur- published accounts of fish fossils from Dubois pose. The fossils collected by Dubois most likely and Selenka collections (Boeseman, 1949; Dubois represent all the fauna encountered the excava- 1907, 1908; Hennig, 1911; Koumans, 1949). Eco- tions, since he was known to collect “everything” logical and size data of fish species were obtained from large mammals to fish bones and mollusc from Fishbase (www.fishbase.org). 22 a b

Sangiran Dome Trinil

Upper Kedung Middle Brubus fauna (Kabuh)

Bapang FM Lower Trinil HK Stratigraphy of this Lowest fauna layer: Fig. 3b and 3c 1.51 Ma Grenzbank Zone Ci Saat Tuff T10 fauna 100

“black clays” “Weicher Sandstein” Rainy season water level Sangiran Fm (Pucangan) Homo erectus Diatomite skullcap and femur “Lowest”, “lower”, “middle” and “upper” refer to tuffs in the section. Dry season water level We follow the chronology of Bettis et “Lapillischicht” al. (2008) and place the base of the

Bapang FM. at 1.51 Ma. We consider marine clays marine Trinil HK to be contemporaneous with “Tonstein” 0 m Lower the Grenzbank zone and thus infer an Lahar age of ~1.5 Ma for Trinil HK

Balanus LS Figure adapted from Indriati and Anton Marine breccia

(2008), based on a Sangiran Puren Fm Puren (Kalibeng) stratigraphic column courtesy of Dr. C.C. Swisher, III. c

Figure 3. a: Stratigraphy of the Plio-Pleistocene Solo Basin. The age of the Grenzbank deposits (≈ Trinil HK) was de- termined by Larick et al. (2001) to be ~1.51 Ma, while others assumed a younger age of ~0.9 Ma (e.g., Bouteaux et al., 2007). The Sangiran Formation is also known as the Pucangan Formation, and the Bapang Formation also as the Kabuh Formation (Duyfjes, 1936). b: Stratigraphy of Trinil HK, the type locality of Homo erectus, according to Dubois (1896). Sequence from top down: modern soil layer, soft sandstone layer, lapillibed or main bone bed (with position of H. erectus skullcap and femur), conglomerate, mudstone, marine breccia. Two river water levels are indicated, the lower one is the level during the dry season and the higher one the level during the wet season. The thickness of the lapillibed is about 1 m, that of the conglomerate about 0.5 m. c: Stratigraphy of the “Pithecanthropusschichten” (Trinil HK) according to Carthaus (1911) in Selenka and Blanckenhorn (1911). This excavation in Grube II (Trench II) by the Selenka expedition was situated at the same place as Dubois’ excavations but more landward (De Vos and Aziz, 1989). 8 = Bone bed, 9 = Plant leave bed, 10 = Sandstone-like tuff (white-striped), 11 = Tuff with loam patches, 12 = Volcanic mud tuff, sandstone, 13 = Sand-stone like tuff (light-coloured), 17 = Soil. The wedge in the lower left of the drawing is a conglomerate underly- ing the bone bed.

Both Dubois and Selenka also assembled exten- not considered in her publication. To obtain a sive collections of fossil shells (Dubois 1907, 1908; more complete picture of paleoenvironmental Dozy, 1911; Martin, 1911; Martin-Icke, 1911). Fur- conditions in Trinil, we identifi ed both non-ma- thermore, fossil shells were excavated at Trinil by rine and marine molluscs in molluscan bulk sam- the Geological Survey of the Netherlands Indies, ples (fossiliferous sediment samples) collected by Bandung, in the 1930’s. The non-marine shells Dubois from the sandstone and andesitic tuff lay- from these collections were studied in detail by ers at Trinil (Fig. 3b, 3c). These samples had not Van Benthem Jutting (1937). She mentioned that been studied before by malacologists and provide marine shells were found at Trinil, but they were new data on the mollusc fauna. They are curated 23 as part of the Dubois Collection at Naturalis, Leiden (collection numbers 1543, 1546, 6900, 8138, 9608, 9609, 9665, 9687, 9691, 9694, 9697, 9779, 9820). Three bulk samples (Trinil 9691, 1546, 9697) were analysed in detail by identifying and counting every recognizable shell larger than 2 mm from 1.5 kg fossiliferous sediment. Data on the mammalian, reptilian and avian faunal composition from Trinil were obtained from pub- lished accounts (e.g., De Vos and Sondaar, 1982; Weesie, 1982; Delfino and De Vos, 2006).

Geochemical analysis – Strontium isotope analyses were applied in order to determine water prove- nance and water salinities of the aquatic paleoen- vironments at Trinil. In well-preserved shells, fish bones, stingray stings and other aquatic fos- sils, Sr isotope ratios of the fossils are unaffected by biological or climatological fractionation processes and reflect the Sr isotope ratio of the host water in which they were growing (Faure, 1986). In the Early Pleistocene there were two main sources of freshwater that determined the strontium isotope ratio (87Sr/86Sr) of waters in the Solo Basin: 1) run-off from the volcano Gunung Merapi on Central Java draining volcanics with Sr isotope values of ~ 0.705-0.706 (Gertisser and Keller, 2003) and 2) run-off from Gunung Lawu on East Java draining volcanics with Sr isotope values of ~ 0.7046-0.705 (Whitford, 1975; Carn and Pyle, 2001). In addition, there potentially was epi- sodic marginal marine influence of seawater with a Sr isotope ratio of ca. 0.7091 (McArthur et al., 2001). Due to the relatively high Sr concentration in seawater (100-1000 times higher than fresh- water; Palmer and Edmond, 1989; Vonhof et al., 1998, 2003), even a minor seawater component in the aquatic system will strongly influence the 87Sr/86Sr of aquatic fossils.

Strontium isotope (87Sr/86Sr ) analyses were car- ried out on a modern freshwater shell from the Figure 4. a: Well-preserved lamellar aragonite of the Solo river collected by Dubois near Trinil, and bivalve Pseudodon vondembuschianus trinilensis (DUB on well-preserved fossil material (seven shells, 5234). b: Well-preserved lamellar aragonite of the bivalve three fish bones) from Trinil and Sangiran Dome Elongaria orientalis (DUB 11364). c: Lamellar aragonite of the gastropod Tarebia cf. granifera (DUB 9963) with minor following the approach and methods outlined aragonite dissolution. in Vonhof et al. (1998, 2003). We analysed spe- cies that we expected to represent a variety of habitats in the Solo Basin. SEM inspection of the fossil shells revealed that the original lamellar aragonite structure was still present (Fig. 4a, 4b) with occasional evidence for minor aragonite dissolution (Fig. 4c). Diagenetic overgrowth was 24 absent. Particularly the absence of diagenetic Piyapong, 2007). Gilles Cuny (pers. comm.) con- aragonite leads us to believe that diagenetic al- cluded that the fossil stingray can be tentatively teration of the original Sr-isotope signal has not assigned to the latter species. A definite identifi- occurred. For isotopic analysis of Sr in shell fos- cation can be made only if complete spines of the sils, about 0.001 g of cleaned HCl-leached shell fossil stingray and of H. chaophraya are found. was dissolved in 1 ml 5 N HAc. After centrifuging the samples within 30 minutes from the start of Faunal analysis: molluscs – Among the mollusc fos- the reaction, the supernatant was pipetted off sils from Trinil (Tables 3 and 4), well-preserved, and Sr was separated by use of an ion exchange fragile species are common, as are paired bi- resin. For Sr isotope analysis of fish bone and valves. Only few abraded specimens were found, spine fossils, a small piece of cleaned bone was the preservation state was very similar for all added to 1 ml 5 N HAc for 30 minutes to dissolve shells. The most abundant species in the Dubois any carbonate present. After centrifuging, the and Bandung collections is the large-bodied (ca. supernatant was pipetted off and discarded, and 100 mm length) pearly freshwater mussel Pseu- about 0.001 g of the remaining leached bone was dodon vondembuschianus trinilensis (Fig. 6a). The dissolved in 3 N HNO3 for subsequent Sr separa- Selenka collection contains only four Pseudodon tion with ‘Elchrom Sr spec’ ion exchange resin. valves although Martin (1911) remarked upon 87Sr/86Sr ratios were determined by standard the abundance (“zahlreich”) of these bivalves in mass spectrometric methods (Thermofinnigan Trinil HK deposits. The collections also contain MAT 261 and 262), and normalized to 86Sr/88Sr = many fragments of Pseudodon shells. The second 0.1194. The average 87Sr/86Sr ratio of the NBS 987 and third-most abundant species are the small standard (n=14) was 0.710245 +/- 0.000009. Sr in gastropod Tarebia granifera and the bivalve Elon- the blanks was < 0.05% of the Sr measured. To garia orientalis. Of the other mollusc species, only obtain an approximate value of the Sr concen- few (~ 1-20) specimens are present. tration of Central-East Javan freshwater, a water sample was taken from the modern Solo river at Van Benthem Jutting (1937) noted conspicuous Waduk Ngablak (7˚51’32” S, 110˚25’26”E) where characteristics of the shell assemblages. Pseu- living bivalve shells were present in the river. The dodon is by far the most numerous species, about sample remained unfiltered and unacidified prior 10 to 200 times as many as shells of the other to analysis. The Sr concentration of the sample species. The Pseudodon shells are characterized was measured using ICP-MS (Thermo electron by uniformity in large size (90 to 120 mm length) X-series II) and linear regression against a single and absence of smaller and juvenile specimens. element Sr standard (CPI). There are only two specimens of 80 mm length or less in the collections from Trinil, namely sam- Results ples 9744 (69 mm) and 9747 (80 mm) in the Du- bois collection. Also the collected fragments do Faunal analysis: fish – In total, we have encoun- not show the occurrence of any young Pseudodon. tered nine fish species in the fossil fauna from Many valves are paired. Two forms of Pseudodon Trinil (Table 1). The collections are numerically shells can be distinguished in the collections, a dominated by catfish remains: Clarias batrachus, broad one and a stretched one, the latter with a Clarias leicanthus, Hemibagrus nemurus, and un- rostrum-like tailend curved downwards. The two identified silurids (Table 2). Two spine fragments different forms are, according to Van Benthem (1639c) from the Dubois collection, identified Jutting (1937), “reaktionsformen” (ecopheno- by Koumans (1949) as “Siluroidae fin spines”, types). The two different forms are frequently were found to be tail spines (stings) of stingrays associated in lots carrying the same field label, (Fig. 5). The spine characteristics (estimated indicating that they were found together as fos- total spine length, lack of dorsal groove) match sils. Another characteristic is that the Pseudodon with those of Pastinachus sephen and Himantura shells were found in a very limited area only: a chaophraya (Schwartz, 2007; Cuny and Piyapong, total of 369 valves is present in collections from 2007). The conspicuous robustness of the spine Trinil itself; four valves were collected from Ke- is similar to the robustness documented from an doeng Broeboes plus two fragmented valves from (incomplete) spine specimen of the Giant Fresh- Tritik, but none from elsewhere on Java. Elongaria water Stingray Himantura chaophraya (Cuny and orientalis shells are also relatively numerous in 25 Current name Synonyms length Common name Habitat

Anabas testudineus * Anabas 25 cm Climbing perch Lakes, rivers, brooks, flooded areas, stagnant water (Bloch, 1792) microcephalus bodies, estuaries; often in areas with dense vegetation. Can walk overland using its auxillary air breathing organ.

Channa cf. striata* Ophiocephalus 100 cm Snakehead Muddy lowland rivers, swamps, estuaries. Air-breather, can (Bloch, 1793) palaeostriata survive periods outside water. Clarias batrachus* Clarias magur 47 cm Walking catfish Lowland streams, swamps, dry river pools, stagnant and (Linnaeus, 1758) muddy water. Can leave the water and walk to migrate to other water bodies using its auxillary air breathing organ. Can tolerate brackish waters. Clarias leiacanthus * Clarias magur 33 cm Forest walking Forest streams, muddy pools. Airbreathing organ. (Bleeker, 1851) catfish Hemibagrus nemurus * Macrones 65 cm Asian redtail Muddy rivers, flooded forests. (Valenciennes, 1840) nemurus catfish Glyphis gangeticus* Carcharias 204 cm Ganges shark Muddy, turbid rivers, lakes and estuaries. (Müller & Henle, 1839) gangeticus, Eulamia gangetica Pristis sp. * Pristis sp. 600 cm Sawfish Rivers, lakes, estuaries, shallow coastal waters Himantura cf. previously not 500 cm Giant Freshwater Sandy bottoms of large rivers and estuaries chaophraya * identified Stingray (Monkolprasit & Roberts, 1990) Carcharius taurus * Odontaspis cf. 320 cm Sand tiger shark Continental shelf up to 190 m deep, shallow bays, (Rafinesque, 1810) cuspidata estuaries, sometimes enters river mouths.

Table 1.The fossil fish of Trinil. Fossil identification, except for Himantura cf. chaophraya, as in Dubois, 1907, 1908; Hennig, 1911; Koumans, 1949; Boeseman, 1949. Current species/family/common names as well as length and habitat information: www.fishbase.org. * edible species. the collections (Table 4) although less so than the unknown from Trinil. Furthermore, low num- Pseudodon shells. Many of the shells are defec- bers of obligate fresh water taxa were found. The tive: in most cases the posterior part is missing. shells are well preserved, and for example several The Elongaria shells have a length of 40 - 60 mm of the Eamesiella valves could be matched. (middle to adult size), and no remains of young individuals (< 25 mm length) are present in the The species composition of the Dubois, Selenka collections. Two shell forms occur side by side in and Bandung collections (Table 4) differs from the samples: one shell form has a stretched and that of the Dubois bulk samples (Table 5). The slightly uplifted posterior end in which the ven- bulk samples contain relatively low numbers of tral side is horizontal or a little convex, and one (marginal) marine species while the other col- shell form has a curved and descending tailend lections do not, but this is because marine shells and a conspicuously concave base-line. were separated from these collections already in The bulk samples collected by Dubois are domi- the 1930’s (Van Benthem Jutting, 1937). The large nated by the gastropods Melanoides aff. tubercu- bivalves Pseudodon and Elongaria are the most nu- lata, Tarebia granifera (Fig. 6f, g) and Thiara scabra. merous shells in the Dubois, Selenka and Pseudodon vondembuschianus trinilensis has not Bandung collections, while they are lacking and been encountered in the samples (except one rare respectively in the Dubois bulk samples. partial Pseudodon valve in sample 1543), and only few, subadult specimens of Elongaria orientalis Faunal analysis: mammals, reptiles, birds – A list were found in only some of the bulk samples. of the mammalian, reptilian and avian species Marine molluscs are present in low numbers. The found at Trinil is presented in Table 6, with an marine chemosymbiont bivalve Eamesiella aff. indication of the typical habitat for each species. corrugata (Fig. 6b-e) was found in eight samples The 18 mammal species are terrestrial (i.e. non- (6900, 9608, 9609, 9665, 9687, 9691, 9694, 9779). aquatic), except for the otter Lutrogale sp. The The three bulk samples that were analysed in de- reptiles are all aquatic or semi-aquatic, and four tail (1546, 9691, and 9697) contain 28 mollusc spe- out of five bird species are (semi-)aquatic. The cies (Table 5). The fauna is dominated by fresh- composition of the fauna indicates a paleoenvi- water to oligohaline cerithoidean species but also ronment consisting of lowland tropical forest, contains 17 brackish-marine species previously grasslands, floodplains, swamps, lakes and riv- 26 Name Dubois Collection Sekenka collection

Anabas testudineus (Bloch, 1792) 3 opercula Channa cf. striata (Bloch, 1793) 2 left interopercula 1 postclavicula 1 right operculum 1 right epi- and ceratohyale 1 basisphenoid fragment Clarias batrachus (Linnaeus, 1758) 3 occipitalia superiora 1 postclavicula 2 left frontalia 6 postclavicula fragments 7 pectoral spines Clarias leiacanthus (Bleeker, 1851) 1 right frontal Hemibagrus nemurus * (Valenciennes, 1840) 9 pectoral spines Siluroidea unidentified 3 pectoral spines 13 pectoral spines 2 pectoral spine fragments 1 dorsal spine Glyphis gangeticus 15 teeth from upper jaw 12 teeth (Müller & Henle, 1839) 1 tooth from lower jaw 2 vertebrae Pristis sp. 1 rostral spine Himantura cf. chaophraya? (Monkolprasit & Roberts, 2 pieces of tail spine 1990) Carcharias taurus (Rafinesque, 1810) 2 teeth with bases Non-identified fish 10 vertebrae 1 tooth 8 vertebrae

Table 2.Fish fossil elements of Trinil. Fossil identification, except for Himantura cf. chaophraya, as in Dubois, 1907, 1908; Hennig, 1911; Koumans, 1949; Boeseman, 1949.

ers. None of the species can be considered to be systems (Whitford, 1975; Carn and Pyle, 2001; typically marine, although at least 11 of the 18 Gertisser and Keller, 2003). These values suggest species are known to occur in estuaries and man- admixture of marine water into the Solo Basin grove areas. freshwater system.

Geochemical analysis – Table 7 presents the Sr To test this, we applied a binary mixing model isotope ratios of several fish and mollusc fos- (Vonhof et al., 1998, 2003) with Central-East Java sils from Trinil (Dubois Collection) and Sangiran freshwater and early to middle Pleistocene sea- Dome (Von Koenigswald Collection) are present- water as endmembers (Table 8). The measured ed, as well as the Sr isotope ratio of a recent shell Sr concentration of the modern Solo river is collected from the Solo river near Trinil. All mol- 0.413 ppm, which is about 4-5 times higher than luscan shells and fish bones –including the sting- expected for freshwater draining volcanic areas ray spines- have Sr isotope ratios lower than with a Sr isotope ratio of ~ 0.705 (Palmer and Ed- the values typical of Early Pleistocene seawater mond, 1989). This high value is likely to be caused (0.709102 – 0709136; McArthur et al., 2001), con- by the strong anthropogenic influence (erosion, firming that these fish and molluscs were living agriculture, industrial pollution) on modern in a non-marine habitat. The Sr isotope ratio of a Javan rivers, thus not being representative for Physunio shell collected by Dubois from the Solo the Sr concentration of Pleistocene East-Central river near Trinil is 0.705499 +/- 0.000011, showing Javan freshwater. Anthropogenic influence on the influence of Gunung Merapi volcanics on the modern rivers is a typical problem in Sr geo- modern river Solo water. In contrast, the lower chemistry (Palmer and Edmond, 1989; Bentley, Sr isotope ratio (0.704946) of a fossil Tarebia shell 2006). Therefore, we also ran the binary mixing from Trinil (sample no. 11422) indicates a rela- model with an inferred typical non-anthropo- tively important contribution of Gunung Lawu genic Sr concentration (0.097 ppm) for volcanic source water to the Pleistocene Trinil aquatic catchments, based on the average Sr concen- habitat. It is striking that several aquatic fossils tration of five rivers draining such catchments (11364, 9694, F588, 9693; Table 7) have Sr isotope (Palmer and Edmond, 1989). The results of the ratios considerably above 0.706, the maximum binary mixing model with the inferred “natural” value expected for Central-East Javan freshwater Sr concentration of 0.097 ppm (Fig. 7a) indicate 27 Figure 5. Stingray spine pieces from Trinil (DUB11639c) tentatively assigned to Himantura cf. chaophraya (Monkolprasit and Roberts, 1990). a: Ventral side of large specimen. b: Dorsal side of large specimen. c: Ventral side of small speci- men (probably juvenile). d: dorsal side of small specimen. The spines have a straight shape and symmetrical rows of barbs. Dorsal surface is smoothly convex, without dorsal groove. The ventral surface has two marginal grooves bordering a flat axial rib. The sides of the rib are squared off, although in a few specimens the marginal grooves slightly undercut the rib. The spines are conspicuously robust with a width of up to 10 mm (range 4-10 mm) and a barb frequency of circa seven barbs per cm (range 5-10 per cm). Based on typical stingray spine proportions, estimated maximum total spine length would have been at least 200 mm. the occurrence of a salinity range between 0.5-5 eral species nowadays living in brackish mudflats, ppt causing low salinity brackish (oligohaline) lagoons and near or in mangroves. The ecological conditions. The results of the binary mixing signature of the mollusc fauna is consistent with model with the “anthropogenic” Sr concentra- that of the fish fauna, indicating predominantly tion of 0.413 ppm (Fig. 7b) indicate that the rela- near-coastal lowland freshwater settings: shal- tively high Sr isotope ratios would reflect a salin- low rivers and lake water with both muddy and ity range of 5-12 ppt, causing low to moderately well-aerated clean sandy bottoms, lagoons and brackish (oligohaline to mesohaline) conditions swamps with low-oxygen and brackish condi- in the Solo Basin at the level of the Trinil HK. tions. The presence of marine shells corroberates occurrence of marine influence in the freshwater Discussion system, in the same way as the presence of the marine sand tiger shark Carcharius taurus. To- Trinil paleoenvironments – The aquatic fossils gether, the mollusc, fish, bird, reptile and mam- found in Trinil HK deposits should be regarded as mal faunas from Trinil indicate the presence of belonging to the same fauna (Dubois, 1908). The a coastal plain environment containing lowland Trinil fish fauna includes species living in turbid tropical forest as well as open grasslands. In these lowland rivers, lakes, areas with submerged trees environments, rivers, lakes, lagoons, swamp for- and aquatic vegetation, swampy areas with low ests and swamps with limited marine influence oxygen content, and estuaries with brackish wa- were present. The Sr isotopic results corroborate ter. Himantura chaophraya is a recently described the presence of mostly freshwater settings with large stingray occurring on sandy bottoms of some marine influence (oligohaline, salinity estuaries and large rivers of Asia and Oceania not exceeding 5 ppt). A modern analogue of the (Monkoprasit and Roberts, 1990). The shark aquatic paleoenvironments at times of deposition Glyphis gangetica as well as the sawfish Pristis sp. of Trinil HK could be the tropical lowland fresh- are also typical freshwater-estuarine dwellers. In water swamp forest biotope, which occurs along contrast, the sand tiger shark Carcharius taurus is the lower reaches of tropical rivers and around a coastal marine species which only rarely enters tropical lakes. An example of this biotope is the river mouths. The mollusc fauna from Trinil HK is Sundarbans freshwater swamp forest, situated dominated by freshwater species, some of which inland of the Sundarbans mangroves in India and may tolerate slightly brackish (lagoonal) condi- Bangladesh. Other examples are the Tonle Sap tions, and contains furthermore relatively low Great Lake in Cambodia, and the Chao Phraya numbers of strict freshwater as well as brackish freshwater swamp forest in Thailand. We have to marine species. The latter group contains sev- compared faunal species lists of Trinil HK with 28 Species name Family name Habitat Pila conica (Gray, 1828)* Ampullariidae Vegetation zone of stagnant water, ponds, swamps Bellamya javanica (Von dem Busch, 1844) Viviparidae Bottom- or plant dweller, lives in ponds and swamps Stenothyra sp. (Robba et al., 2003) Stenothyridae Brackish water mudflats Digoniostoma truncatum (Eydoux and Souleyet, Bithyniidae Bottom- or plant dweller, lives in ponds and swamps 1852) Cerithium sp. Cerithiidae Shallow marine Brotia testudinaria (Von dem Busch, 1842) Pachychilidae Eurytopic: in running as well as stagnant freshwater, between sea level and 1500 m altitude Melanoides aff. tuberculata (Müller, 1774)* Thiaridae Ponds, rivers, lakes, estuaries; can tolerate brackish water Melanoides cf. plicaria (Born, 1780)* Thiaridae Uncertain Tarebia granifera (Lamarck, 1822)* Thiaridae Lakes, rivers, shallow fast-flowing freshwater streams, ponds and swamps, occasionally in slightly brackish water Thiara zollingeri fennemai (Martin, 1905) Thiaridae Freshwater, may have tolerated brackish water Thiara cf. tjemoroensis (Martin, 1905)* Thiaridae Uncertain Thiara scabra (Müller, 1774)* Thiaridae From sea level up to 2000 m, in stagnant or running water, also in brackish estuaries Melongena sp. Melongenidae Estuaries, salt marshes, mangroves, shallow marine biotopes Quirella cf. lyngei (Robba et al., 2003) Pyramidellidae (marginal) marine, parasite Cingulina sp. Pyramidellidae (marginal) marine, parasite Didontoglossa cf. decoratoides (Habe, 1955) Retusidae Sandy mud bottoms, 10-50 m depth Gyraulus convexiusculus (Hutton, 1849) Planorbidae Vegetation zone of stagnant water, ponds, swamps Lymnaea javanica (Mousson, 1849) Lymnaeidae Vegetation zone of stagnant water, ponds, swamps Ameria duboisi (v. Benthem Jutting, 1937) Lymnaeidae Vegetation zone of stagnant water, ponds, swamps Quirella cf. lyngei (Robba et al., 2003) Pyramidellidae Marine soft bottom Jupiteria sp. Nuculanidae Marine soft bottom Anadara cf. granosa (Linnaeus, 1758) Arcidae Tidal flat and muddy bottoms seaward fringe of mangroves Mytilidae indet. Mytilidae Marine or marginal marine, substrate dependent Eamesiella aff. corrugata (Deshayes, 1843) Lucinidae Marine to brackish chemoautotrophe Cycladicama cumingii (Hanley, 1844) Ungulinidae Marine, sand-mud bottom, 10-50 m depth Tellimya sp. 1 (Robba et al., 2002) Montacutidae Marine, parasite Arcopagia pudica (Hanley, 1844) Tellinidae Muddy bottom infralittoral zone and in front of mangroves Arcopagia yemensis (Melvill, 1898) Tellinidae Marine soft bottom Gari sp. Psammobiidae Marine soft bottom Theora lata (Hinds, 1843) Semelidae Marine soft bottom Elongaria orientalis (Lea, 1840)* Unionidae Lakes and rivers Rectidens sumatrensis (Dunker, 1852)* Unionidae Lakes and rivers Pseudodon vondembuschianus trinilensis* Margaritiferidae Forest streams and sandy, shallow areas in lakes and rivers (Dubois, 1908) Corbicula pullata (Philippi, 1850)* Corbiculidae Streams, quiet fresh to occassionally brackish waters Corbicula gerthi (Oostingh, 1935)* Corbiculidae Streams, quiet fresh water Geloina sp. Corbiculidae Estuaries, mud flats, mangroves Dentalium sp. Dentaliidae Marine

Table 3. Mollusc species from Trinil. Fossil identification based on Van Benthem Jutting (1937) and our analysis of previously unstudied bulk samples collected by Dubois and curated at Naturalis, Leiden. *species assumed to be edible. Habitat information from Dillon (2000) and Robba et al. (2002, 2003). species lists of the Sundarban freshwater swamp ban wetlands. In total, 24 of the 28 species from forest, including the oligohaline eastern part Trinil correspond completely (at species level) of the Sundarban mangrove system in Bangla- or closely (at genus level) to species occurring in desh. Of the nine fish species documented from the Sundarban wetland. Two other species from Trinil HK, eight occur in the Sundarban wetlands Trinil, Stegodon trigonocephalus and Duboisia san- (Sanyal, 1999). The stingray Himantura chaophraya teng are extinct endemics that have no present- is absent from the Sundarbans (where other Hi- day counterpart. We conclude that the nature mantura species do occur) but H. chaophraya does (in terms of local environmental conditions and occur in the Chao Phraya freshwater swamp faunal composition) of the aquatic environment forest ecoregion in Thailand (Monkolprasit and of Trinil HK is comparable to that of the modern Roberts, 1990). In Table 9, we have compared the coastal tropical freshwater swamp forest biotope. mammalian, reptilian and avian species list from However, this does not imply that the Trinil HK Trinil HK with species occurring in the Sundar- environment is comparable to the Sundarbans, 29 Species name Dubois Selenka Geol. S.B.

Pila conica 2 1 - Bellamya javanica 2 3 - Digoniostoma truncatum - 3 - Brotia testudinaria - 15 8 Tarebia granifera 14 16 29 Thiara zollingeri 5 2 - fennemai Table 4. Number of shell fossils in collections of Dubois, Thiara scabra - 2 - Selenka and the Geological Survey Bandung. These Gyraulus convexiusculus - 1 - collections contain excavated or hand-picked shells dominated by large specimens (size typically > 10 mm). Lymnaea javanica 11 6 - Bivalve species are reported as halves (two valves make Ameria duboisi 2 1 - a single specimen). Shells from Dubois bulk samples are Elongaria orientalis 22 / 2 8 / 2 14 / 2 not included. The gastropods from the Selenka collection Rectidens sumatrensis 2 / 2 - 9 / 2 derive from layers just above and just below the Haupt- Pseudodon 263 / 2 4 / 2 102 / 2 knochenschicht and from the Hauptknochenschicht itself vondembuschianus (Martin-Icke, 1911). The provenance of the bivalves from trinilensis the Selenka collection is not clearly indicated (“Pithecan- Corbicula pullata 1 / 2 - - thropusschichten”; Martin, 1911). The same applies to the Corbicula gerthi 15 / 2 - - shells from Dubois and Bandung collections.

Tonle Sap or Chao Phraya freshwater swamp for- garia are the most numerous shells in the Dubois, ests in terms of scale, geography and geology. Selenka and Bandoeng collections, while they are De Vos et al. (1982) studied the composition of not or hardly present in the Dubois bulk samples. the mammalian fauna from Trinil HK and in- The absence of these shells in the bulk samples is ferred the presence of an open grassland and puzzling, since Dubois (1908, p. 1249) specifically savanna ecosystem in the Trinil area. This may stated that two species of freshwater mussel, seem contradictory to the presence of a wetland one large (Pseudodon; JJ) and one small (Elongaria; system, but for instance the Tonle Sap freshwater JJ), are the most numerous (“allerhaüfigsten”) swamp forest biotope includes extensive areas mollusc species at Trinil. The stratigraphic prov- of seasonally inundated grasslands, the so-called enance of the bulk samples is known, they all hydromorphic savanna (Campbell et al., 2006). derive from the soft sandstone layer (see caption We conclude that the aquatic part of the Trinil Table 5; Fig. 3b; layers 10-14 in Fig. 3c). We there- area during deposition of Trinil HK contained riv- fore assume that the many large bivalves in the ers, lakes, swamp forests, lagoons and marshes collections derive primarily from the layer below with minor marine influence, laterally grading the soft sandstone layer, namely the Hauptkno- into grasslands possibly subjected to regular chenschicht (“Lapillischicht” or main bone bed) inundation. Bettis III et al. (2008) reconstructed itself. The abundance of large bivalves in this paleoenvironments in the Sangiran area. They layer, in contrast to the rarity in the layer above, found that during Trinil HK times (~ 1.5 Ma, Cycle will be discussed further on in the discussion sec- 1 of the Bapang Formation), the Sangiran land- tion. scape consisted of low-lying, frequently flooded areas which supported a moist savanna with Availability and “catchability” of aquatic food re- scattered trees and shrubs. Riparian forest occu- sources – The nine fish species from Trinil HK are pied the active river channel belt where shifting edible by humans, and could have been possible channels left many sandbars and shallow aban- food resources for Homo erectus. Since the earliest doned channels. This reconstruction agrees well known barbed harpoons made of bone date from with our interpretation of paleoenvironments at ~ 90 kya (Brooks et al., 1995), it is unlikely that Trinil. H. erectus could have used tools such as bone fish hooks or harpoons to capture live fish from deep- The mollusc fauna from Trinil HK requires a er water. Lack of these tools most probably elimi- more detailed interpretation because of the nates the availability of the large elasmobranch observed difference in species composition be- fish Glyphis gangeticus (Ganges shark), Pristis sp. tween Dubois bulk samples, and shell collections (Sawfish) and Carcharius taurus (Sand tiger shark) made by Dubois, Selenka and Geological Survey as “catchable” food resources. Spearing of sting- Bandoeng. The large bivalves Pseudodon and Elon- rays (Himantura cf. chaophraya) with a pointed 30 Figure 6. Selected molluscs from Trinil HK, collected by the Dubois Expedition, 1900. a: Pseudodon vondembuschianus trinilensis (Dubois, 1908). b-e: Eamesiella aff. corrugata (Deshayes, 1843). f-g: Tarebia granifera (Lamarck, 1822).

documented earliest use of composite bone tools (bamboo) stick or spear may have been a possibil- dates from the Middle Stone Age (MSA) in Africa ity. Oppenoorth (1936) mentioned that modern in association with H. sapiens (d’Errico and Hen- humans from Indonesia use stingray spines as shilwood, 2007) and there is no indication that spear tips, and suggested that the barbed sting- Javanese H. erectus used this type of advanced ray spine, found at the same level and at a dis- technology. tance of ~10 m from H. erectus calvarium VI at Ngandong, served the same purpose. However, Hemibagrus nemurus (Asian redtail catfish) lives 31 Species name 9691 1546 9697 Bellamya javanica (Von dem Busch, 1844) 1 4 fr. 10 Stenothyra sp. (Robba et al. 2003) 1 85 Digoniostoma cf. truncatum (Eydoux and Souleyet, 1852) 4 Bithinyidae sp. operculum 1 Cerithiidae sp. 2 3 Melanoides aff. tuberculata (Müller, 1774) 138 c. 780 Melanoides cf. plicaria (Born, 1780) 21 51 31 Tarebia granifera (Lamarck, 1822) 522 72 >1000 Thiara scabra (Müller, 1774) 754 9 c. 600 Thiara cf. tjemoroensis (Martin, 1905) 16 4 24 Neogastropoda indet. 1 Quirella cf. lyngei (Robba et al., 2003) 1 12 Cingulina sp. 1 Didontoglossa cf. decoratoides (Habe, 1955) 6 Dentalium sp. 2 Jupiteria sp. 1/2 2 + 3/2 Anadara cf. granosa (Linnaeus, 1758) 1 fr. Mytilidae indet. 1/2 Eamesiella aff. corrugata (Deshayes, 1843) 99 /2 1 fr. 59/2 Cycladicama cumingii (Hanley, 1844) 1/2 8/2 Tellimya sp.1 (Robba et al., 2002) 1/2 Arcopagia yemensis (Melvill, 1898) 10 /2 4/2 Arcopagia pudica (Hanley, 1844) 1/2 Gari sp. 1/2 Theora lata (Hinds, 1843) 5/2 8/2 Elongaria orientalis (Lea, 1840) 1/2 1/2 + 2 fr. 1/2 + 2 fr. Corbicula pullata (Philippi, 1850) 13 / 2 26/2 35/2 Corbicula gerthi (Oostingh, 1935) 6 / 2 3/2 3/2

Table 5. Molluscs counted from bulk samples Trinil 9691, 1546, 9697. Countable shells larger than 2 mm were counted from 1.5 kg. bulk sediment sample. Bivalve species are reported as halves (two valves make a single specimen). Bulk samples derive from the sandstone and andesitic layers (soft sandstone layers, Fig. 3b) above the “Lapillischicht”. Dubois uses the words “zandsteen” (sandstone) and “tuf” (tuff) in ways that seem to indicate the same. For instance, in one of his notebooks (p. 245, Dubois Archive, Box 3) he mentions “andesietzandsteen bij Trinil” with the word “tuf” written just above “zandsteen”. The labels of the bulk samples are marked “zandsteen” or “andesiet tuf”. We assume he refers to the same layer: “weicher sandstein” (soft sandstone) in Fig 3b, which has been presented in a more detailed way by Carthaus (layers 10-13, Fig. 3c).

in large muddy rivers where it would be hard to We therefore infer that these four fish species catch without technology. However, they enter would have been catchable prey for Homo erectus. flooded forests to spawn in summer (Roberts, The species are known as popular and nutritious 1993). This would facilitate catching the fish (e.g., food for modern human populations (Talwar and by hand or clubbing) when they were in shallow Jhingran, 1991). water among the roots of trees. The fish species Anabas testudineus (Climbing perch), Channa cf. At least 11 out of the 32 mollusc species from striata (Snakehead), Clarias batrachus (Walking Trinil HK (Table 3) are edible by humans (Van catfish) and Clarias leicanthus (Forest walking cat- Damme, 1984; Kress, 2000; IBISWorld, 2003). The fish) have auxillary breathing organs permitting species occur in shallow water and can be har- occasional (often seasonal) overland excursions vested by hand (e.g., Yang, 1990). Shells of three to migrate to other water bodies. Because of their pearly freshwater mussel species (Pseudodon, Elon- considerable size (25 - 100 cm), such “crawling” garia and Rectidens) and of the gastropod Pila have fishes on land or in very shallow water would been found in an early Holocene kitchen midden have been attractive and easy targets for omnivo- in Sampung Cave on Java, and are still consumed rous terrestrial predators without boats or spe- by modern humans on Java (Van Es, 1929; Van cialised fishing tools. For instance, hand capture Benthem Jutting, 1932), confirming edibility and of Snakehead (and other aquatic animals) is prac- dietary value of these species for hominins. We ticed by modern humans in the dry season along conclude that at least four fish species (Table 1) the Mekong river in Cambodia (Deap et al., 2003). and 11 mollusc species (Table 3) were potential 32 Mammalia Family Habitat Panthera tigris (Linnaeus, 1758) Felidae Tropical and evergreen forests, woodlands, grasslands, rocky country, savannas, swamps, mangrove forests. Strong swimmer. Felis (=Prionailurus) bengalensis (Kerr, Felidae Forests and rainforests in low and mountainous areas, usually not in 1792) arid areas. Lives close to watercourses, also in mangroves. Cuon (=Mececyon) trinilensis (Janensch, Canidae Large variety of habitats: dry plains, forests, shrublands, grasslands, 1911) mangroves. Rhinoceros sondaicus (Desmarest,1822) Rhinocerotidae Lowland rainforest, wet grasslands and large floodplains, mangroves Stegodon trigonocephalus (Martin, 1887) Stegodontidae Unknown. Capable swimmer Bubalus palaeokerbau (Dubois, 1908) Bovidae Probably wet habitats ranging from riverine forests and grasslands, to marshes and swamps Bibos palaesondaicus (Dubois, 1908) Bovidae Probably woodlands, close to water Duboisia santeng (Dubois, 1891) Bovidae Probably forests Muntiacus muntjak (Zimmerman, 1780) Cervidae Forests, grasslands, savannas, tropical deciduous forests, tropical scrub forests. From sea level up to 3000 m. Never far from water. Axis lydekkeri (Martin, 1892) Cervidae Probably forests, grassy floodplains Cervus sp. Cervidae Probably forests, grasslands, marshes Sus brachygnathus (Dubois, 1908) Suidae Probably forests, grasslands Hystrix (=Acanthion) brachyura (Linnaeus, Histricidae Variety of habitats: deserts, rocky areas, mountains, savannas, and 1758) forests Lutrogale sp. Mustelidae Probably swamp forests, freshwater wetlands, forested rivers, lakes Rattus trinilensis (Musser, 1982) Muridae Unknown Macaca fascicularis (Raffles, 1758) Cercopithecidae Forests, riverine and swamp forests, mangroves. Strong swimmer Trachypithecus cristatus (Raffles, 1821) Cercopithecidae Forests, coastal areas, mangroves, and riverine forests Homo erectus (Dubois, 1892) Hominidae Probably upland areas, savannas, riverine areas, coastal deltas Reptilia Crocodylus siamensis (Schneider, 1801) Crocodylidae Freshwater swamps, rivers, lakes, sometimes in estuaries. Gavialis bengawanicus (Dubois, 1908) Gavialidae Probably rivers Batagur sp.# Geoemydidae Probably rivers and mangroves Trionyx sp.# Trionychidae Probably rivers, lakes Hardella isoclina# (Dubois, 1908) Bataguridae Probably rivers, lakes Varanus sp. Varanidae Probably rivers, grasslands, forests, swamps, mangroves Aves Leptoptilos cf. dubius (Gmelin, 1789) Ciconiidae Tropical lowland wetlands Ephippiorhynchus cf. asiaticus (Latham, Ciconiidae Tropical lowland wetlands and marshes 1790) Branta cf. ruficollis (Pallas, 1769) Anatidae Grassland, freshwater and coastal wetlands; breeding in the Arctic, wintering in southern areas Tadorna tadornoides (Jardin & Selby, 1828) Anatidae Lakes; breeding in Australia, wintering in northern areas Pavo muticus (Linnaeus, 1766) Phasianidae Forests, grasslands, savannas, scrubland. Capable swimmers, foraging on riverbanks as well as in streams and marshes

Table 6. Mammal, reptile and bird species from Trinil. Based on published accounts (De Vos & Sondaar, 1982; Weesie, 1982; De Vos, 1994; Delfino & De Vos, 2006). #: The aquatic turtles have not been identified with certainty and are in need of revision. Habitat information from Francis (2008), Daniel (2002) and Robson (2000).

food sources for Homo erectus on Java. munities, and documented 121 records of inter- tidal predation among 38 species of terrestrial Probability of aquatic exploitation by hominins in mammals. For instance, mice, rats, pigs, chacma coastal habitats – If aquatic resources such as mol- baboons, brown bears, black bears, striped and luscs and fish were available for hominins on spotted hyenas, coyotes, domestic dogs, grey and Java, what is the probability that they indeed red wolves, jackals and foxes in coastal habitats consumed these resources? In coastal areas, ter- are all known to catch and consume crabs, mol- restrial predators often consume aquatic foods luscs, fish and other aquatic fauna (Carlton and and have a considerable impact on the local Hodder, 2003; Smith and Partridge, 2004). aquatic ecosystem (Polis and Hurd, 1996; Roth, 2003). Systematic, often seasonal, predation by Climatic and seasonal characteristics may trig- non-human terrestrial mammals on freshwater ger systematic aquatic exploitation. For instance, and marine fauna occurs widely. Carlton and mammals living in perennially or seasonally im- Hodder (2003) reviewed occurrence of terrestrial poverished near-coastal systems may turn to the mammals as predators in marine intertidal com- adjacent and potentially more productive aquatic 33 No. Genus/species Location Sr isotope ratio DUB1639c Himantura cf. chaophraya? Trinil 0.705897 +/- 0.000007 DUB1646 Unidentified fish vertebra Trinil 0.705839 +/- 0.000011 DUB5234 Pseudodon vondembuschianus trinilensis Trinil 0.706146 +/- 0.000014 DUB11422 Tarebia granifera Trinil 0.704946 +/- 0.000011 DUB11364 Elongaria orientalis Trinil 0.707568 +/- 0.000008 DUB9694 Tarebia granifera Trinil 0.708345 +/- 0.000008 DUB9694 Lucina sp. Trinil 0.708723 +/- 0.000009 F588* Himantura cf. chaophraya? Sangiran 0.707636 +/- 0.000009 DUB9963 Tarebia granifera Cenklik (Sangiran) 0.708208 +/- 0.000009 DUB9963 Lucina sp. Cenklik (Sangiran) 0.708587 +/- 0.000013 ** Physunio eximius Solo river, Trinil 0.705499 +/- 0.000011

Table 7. Bulk Sr isotope ratios of fish and molluscan fossils from the Solo Bain. DUB: Dubois Collection, Leiden. *Von Koenigswald Collection, SMF. **recent from Solo river near Trinil, Dubois Collection housed at the ZMA-UvA. In bold: Sr isotope ratios higher than expected for Central-East Javan freshwater.

[Sr] “anthropogenic” Javan freshwater 0.413 ppm (measured) [Sr] “non-anthropogenic” Javan freshwater 0.079 ppm (inferred; Palmer & Edmond, 1989) [Sr] seawater 7.8867 ppm (Vonhof et al, 1998) Sr isotope ratio freshwater endmember 0.704946 (measured Tarebia 11422) Sr isotope ratio Early Pleistocene seawater 0.709102 (McArthur et al, 2005) Sr isotope ratio Middle Pleistocene seawater 0.709136 (McArthur et al, 2005)

Table 8. Input for binary mixing model.

The literature cited above shows that system- system for food. In the arid deserts adjacent to atic aquatic exploitation (either year-round or the Gulf of Mexico, coyotes (Canis latrans) feed seasonal) by terrestrial mammals is normal and on a variety of aquatic organisms, including sea predictable mammalian behaviour when 1) the turtles, marine mammals, fish, birds, inverte- mammal is omnivorous, 2) living in a coastal ma- brates and algae (Rose and Polis, 1998). Chacma rine or freshwater habitat, 3) where nutritious baboons (Papio ursinus) are known to capture and and catchable aquatic prey is available. Consid- consume aquatic molluscs and crustaceans espe- ered in the perspective of aquatic exploitation cially when the protein content of their terres- by terrestrial mammals in coastal habitats, the trial plant food is low (Avery and Siegfried, 1980). systematic and seasonal aquatic exploitation by In other instances, seasonal abundance of aquatic Homo sapiens (Marean et al., 2007) and H. nean- foods is a positive attractor for aquatic exploita- derthalensis (Stringer et al., 2008) does not differ tion. Systematic seasonal aquatic exploitation from that of other mammals. Also, transport has been documented for of aquatic prey to a base (such as a cave, in the brown bears and black bears preying on spawn- case of H. sapiens and H. neanderthalensis) is not ing salmon in late summer and early fall “modern” behaviour. For instance, Navarrete (Hilderbrand et al., 1999; Jacoby et al., 1999). and Castilla (1993) reported that Norway rat Coastal brown bears in Alaska dig up and con- burrows in coastal Chile contain remains of ~40 sume soft-shelled clams and razor clams on tidal intertidal prey species such as limpets, bivalve flats in early summer (Smith and Partridge, molluscs, crabs and fish. Erlandson and Moss 2004). A recent study by Darimont et al. (2008) (2001) provide many more examples of terrestrial has shown that grey wolves (Canis lupus) prefer- omnivorous animals transporting aquatic food entially feed on salmon in autumn, even when (remains) to dens, nests, burrows and caves on their terrestrial prey (deer) is abundantly pres- land. A label of “modernity”, if applicable at all to ent and in good condition. Darimont et al. (2008) aquatic exploitation, should perhaps be reserved concluded that the high nutritious value of the for aquatic exploitation with evidence of ad- salmon (especially the fatty acid DHA), and the vanced technology such as fish hooks and boats. fact that it is a “benign” prey that does not fight The assumption, that early hominins living in a back, are probably reasons for the wolves to pre- coastal habitat with catchable nutritious aquatic fer salmon over deer. fauna were restricted to eating terrestrial re- sources, does not agree with published accounts 34 A "non-anthropogenic" "anthropogenic" 0.7095 B 0.7095

0.7085 0.7085 Sr Sr 0.7075 0.7075 86 86 Sr/ Sr/ 0.7065 Brackish 0.7065 Brackish 87 87 oligohaline: oligohaline: 0.7055 0.5 - 5 psu 0.7055 0.5 - 5 psu

0.7045 0.7045 0 2 4 6 8 10 0 2 4 6 8 10 Salinity (psu) Salinity (psu)

Figure 7. Mixing hyperbolas of the freshwater versus seawater end members for Pleistocene Trinil. A: mixing curve calculated with inferred “non-anthropogenic” Solo river Sr concentration of 0.097 ppm. B: mixing curve calculated with measured “anthropogenic” Solo river Sr concentration of 0.413 ppm. Salinity expressed as psu (practical salinity units). The outcome of the mixing model is not sensitive to the values for seawater Sr isotope ratios changing over time in the Early Pleistocene (0.709102 - 0.709136; McArthur et al., 2001) so chronology uncertainties do not affect the results.

0.710 Brackish-fully marine water 0.709

0.708 Brackish water

Sr 0.707 86 Freshwater

Sr/ 0.706 87

0.705

0.704

0.703

Lucina Lucina Tarebia Tarebia Tarebia Physunio HimanturaPisces sp. Elongaria Himantura Pseudodon Trinil Sangiran Solo

Figure 8. Sr isotope ratios of aquatic fossils from Trinil and Sangiran, and of a Physunio shell from the modern Solo river. The dotted rectangle indicates the Sr isotope ratios corresponding to a brackish salinity range (oligohaline: 0.5 - 5 psu: practical salinity units), based on results of the mixing model using the “non-anthropogenic” freshwater Sr concentration (fig. 7).

of common mammalian behaviour. Therefore, mammal Homo erectus was living in the wetland instead of having to provide evidence of aquatic habitat of the Solo Basin (Sangiran and Trinil), as exploitation before it is considered as a realistic well as in the coastal delta habitat of Mojokerto option, we propose that the default assumption (Huffman et al., 2006). Edible, nutritious aquatic in hominin evolutionary research should be that fauna was available and catchable. Thus, it is omnivorous hominins in coastal habitats with valid to hypothesize that H. erectus on Java con- catchable aquatic fauna could have consumed sumed aquatic resources. The next step will be aquatic resources. to test the hypothesis. As this concerns the Early Pleistocene time period, we expect that it will be Significance of the aquatic fossil assemblage in the relatively difficult to find unequivocal “smoking Trinil collection – In our study of aquatic paleoen- gun” evidence for possible aquatic exploitation, vironments at Trinil we have demonstrated such as hominin tools or bones in a cave with that all three conditions for aquatic exploita- cut-marked or burned aquatic fossils. However, tion by terrestrial mammals are met in the Early because aquatic food sources contain constitu- Pleistocene on Java. The omnivorous terrestrial ents such as the fatty acid DHA (Kainz et al., 2004) 35 Trinil Sundarban freshwater swamp forest Mammalia Mammalia Panthera tigris Panthera tigris (Tiger) Panthera pardus (Leopard) Felis (=Prionailurus) bengalensis) Felis bengalensis (Leopard cat) Felis chaus (Jungle cat) Felis viverrina (Fishing cat) Manis crassicaudata (Indian pangolin) Cuon (=Mececyon) trinilensis Cuon alpinus (Dhole/Asiatic wild dog)& Canis aureus (Golden jackal) Vulpes vulpes (Red fox) Rhinoceros sondaicus Rhinoceros sondaicus (Javan rhinoceros) Rhinoceros unicornis (One-horned rhinoceros) Stegodon trigonocephalus Bubalus palaeokerbau Bubalus bubalus (Water buffalo) Bibos palaesondaicus Bos (=Bibos) gaurus (Indian Bison) Bos (=Bibos) frontalis (Gaur) Duboisia santeng Muntiacus muntjak Muntiacus muntjak (Barking deer) Axis lydekkeri Axis porcinus (Hog deer) Axis axis (Chital) Cervus sp. Cervus duvaucelii (Swamp deer) Cervus axis (Spotted deer) Cervus unicolor (Sambhar deer) Sus brachygnathus Sus scrofa (Wild boar) Hystrix (=Acanthion) brachyura Hystrix brachyura (Malayan porcupine) Lutrogale sp. Lutrogale perspicillata (Smooth-coated otter) Aonyx cinera (Oriental small-clawed otter) Rattus trinilensis Golunda ellioti (Indian bushrat) Macaca sp. Macaca mulatta (Rhesus macaque) Trachypithecus cristatus (Silvered leaf monkey) Homo erectus Homo sapiens (Modern human) Reptilia Reptilia Crocodylus siamensis Crocodylus palustris (Marsh crocodile) Crocodylus porosus (Estuarine crocodile) Gavialis bengawanicus Gavialis gangeticus (Gharial) Batagur sp.# Batagur baska (River terrapin) Trionyx sp.# Trionyx gangeticus (Indian softshell turtle) Hardella isoclina# Hardella thurii (Crowned river turtle) Varanus sp. Varanus favescens (Yellow monitor) Varanus bengalensis (Common Indian monitor) Varanus salvator (Water monitor) Aves Aves Leptoptilos cf. dubius Leptoptilos dubius (Greater adjutant) Ephippiorhynchus cf. asiaticus Ephippiorhynchus asiaticus (Black-necked stork) Branta cf. ruficollis Tadorna tadornoides Tadorna ferruginea (Ruddy shelduck) Pavo muticus

Table 9. Comparison of mammal, reptile and bird species composition of Trinil and recent Sundarban freshwater swamp forest. The Trinil faunal list is complete (De Vos & Sondaar, 1982; Weesie, 1982; De Vos, 1994; Delfino & De Vos, 2006). The species list from the Sundarban freshwater swamp forest is not complete but contains the larger mammals (27 out of ca. 35 mammal species, i.e. excluding bats, mice etc), and a selection of reptiles and birds (Gopal and Chauhan, 2006; www.worldwildlife.org/wildfinder; Francis, 2008; Daniel, 2002; Robson, 2000). &: Historical range of Cuon alpinus included the Sundarban wetlands; still present in the Myanmar mangroves (Oo, 2002). #: The aquatic turtles have not been identified with certainty and are in need of revision.

with strong physiological effects on brain gene aquatic foods. expression, development and cognition (Calde- ron and Kim, 2004; Kitajka et al., 2004; Kawakita It would theoretically be possible to test the et al., 2006), it is important to actively search hypothesis of aquatic exploitation by measur- for possible subtle clues indicating early use of ing stable isotope ratios of nitrogen and carbon 36 in dental collagen (Lee-Thorp and Sponheimer, tion (Van Benthem Jutting, 1937). Instead, the 2006; Richards et al., 2006; Richards, 2007) of fos- discrepancies suggest that the Pseudodon shells sil Homo erectus teeth. However, the antiquity of could have been brought together, prior to fos- Javan H. erectus teeth most likely precludes the silization, by a size-selective collecting agent who extraction of well-preserved collagen and thus may have used them for consumption of mollus- the study of N and C isotope ratios. A further can flesh. drawback is that isotopic analyses involve de- structive sampling of precious hominin fossil The Elongaria shell assemblage collected from teeth. A non-destructive approach is to focus Trinil is in these aspects comparable to the Pseu- on anomalies in species composition and ta- dodon assemblage: a relatively large number of phonomy of the aquatic fossil assemblages from shells, no young individuals but only adults, two hominin sites. In hominin sites whith possible shell forms mixed in single field lots. It is strik- signs of fish exploitation, the number of fish fos- ing that the posterior part of the Elongaria shells sil elements is very high: for instance Stewart is often missing. In a Holocene kitchen midden (1994) has documented recovery of thousands of from Sampung Cave on Java, many Pseudodon and fossils of the catfish Clarias batrachus from Bed I Elongaria shells have been found among mammal, and Bed II at Olduvai Gorge. The total number of bird and fish remains, together with human tools fish fossil elements recovered from Trinil is low, (Van Es, 1930). Two forms of Elongaria shells were thus providing no indication of exploitation of present in the Sampung Cave kitchen midden this possible resource at Trinil. (Van Benthem Jutting, 1937), just as in the Trinil collections. Van Benthem Jutting (1932, p. 105) The number of shells of most of the molluscan writes: “In the Lamellibranchs (bivalves, JJ), as far species is also low and in the same order of mag- as they have been shattered, invariably the siph- nitude as the fish species fossils, again showing onal region of of the valves is missing to a larger no indication for possible exploitation. However, or a smaller extent. Apparantly the people duly the presence of a relatively large number of recognised this posterior end as the most fragile only adult, large-size Pseudodon shells excavated part of the shell”. The Elongaria assemblage from from a very limited area (Hauptknochenschicht Trinil, just like Pseudodon, appears to indicate in Trinil), in both Dubois and Bandung collec- collection by a selective agent for the purpose of tions, is a discrepancy in the aquatic assemblage mollusc consumption. The Pseudodon and that merits further attention for these shells. Elongaria assemblages from Trinil have the char- Collector’s bias (preferring large-size Pseudodon acteristics of shell middens (e.g., Waselkov, 1987; shells) could have played a role. But then Du- Rosendahl et al., 2007): large adult shells only, bois and Bandung collectors (excavating about many complete shells, no signs of damage due thirty years apart) would have had exactly the to water rolling, signs of damage due to being same bias, which seems unlikely. In addition, the deliberately opened, presence of human (ho- fact that Pseudodon fragments were collected as minin) bones in the same layer. We conclude well, indicates that the collectors did not pick up that they represent a subtle clue for possible only “nice” specimens. It appears that they col- aquatic predation by non-hominins or by homi- lected a representative sample, as is also noted nins. A possible non-hominin predator could be by Van Benthem Jutting (1937). It is highly un- the otter Lutrogale sp., although the presentday likely that the lack of juvenile shells constitutes Smooth-coated otter Lutrogale perspicillata is not a preservation bias against smaller and thinner known to produce shell middens. This otter preys shells: smaller and fragile specimens of various on fish, crustacea, molluscs, frogs, turtles and other species are present. The fact that many birds, using its molars to crush molluscs (Gurung of the Pseudodon valves are still paired and well- and Singh, 1996). In case Lutrogale was the non- preserved would suggest that the mollsucs were hominin mollusc predator at Trinil, we would ex- not dead and transported by water before fossil- pect mainly shell fragments and shells with bite ization, but were buried in live position. However, marks, instead of the many undamaged Pseudodon the complete absence of small, juvenile shells valves present in the collections. as well as the mixed occurrence of two differ- ent (but equally large-sized) shell forms argues In case Homo erectus at Trinil collected Pseudodon against interpretation of burial of a live popula- and Elongaria molluscs for consumption, we 37 predict that traces of handling and processing an ecological point of view, the default assump- (such as typical breakage patterns or cut marks tion in hominin evolutionary research should on the shells) may be present in the shell collec- be that omnivorous hominins in coastal habi- tions. A study investigating damage patterns and tats with catchable aquatic fauna could have handling traces on Pseudodon and Elongaria shells consumed aquatic resources. Further, we have from Trinil is currently underway and will be re- demonstrated that conditions for aquatic ex- ported elsewhere. ploitation by terrestrial mammals are met in the Early Pleistocene on Java: it is plausible that Homo Another factor that deserves further investiga- erectus on Java consumed aquatic resources. One tion is how climate (or climate change) could way to test the hypothesis of aquatic exploita- have influenced dietary preference and prey tion is to carry out a taphonomic analysis of the selection of Homo erectus on Java. Bettis III et al. aquatic fossils associated with hominin fossils. (2008) suggest that H. erectus populations inhab- The observed midden-like characteristics of Pseu- iting Sundaland (including Sangiran and Trinil) dodon and Elongaria shell assemblages from Trinil became environmental refugees repeatedly dur- are an indicator of possible collection by a selec- ing the Pleistocene, especially during glacial tive agent for the purpose of aquatic mollusc terminations and interglacials. These periods consumption. These shell assemblages are cur- were characterised by sea level rise and increased rently being studied to investigate if any hominin atmospheric moisture, thus reducing the extent or non-hominin predation traces are present. of dry savanna and open forest. Bettis III et al. Also, the role of climate (change) influencing (2008) imply that these conditions were unfa- hominin prey selection should be investigated. vorable for H. erectus inhabitants, and may have We feel that the possible physiological implica- forced them into highlands during these periods. tions of aquatic resource use for hypotheses on We have shown that H. erectus, in a similar way as hominin encephalization and cognition merit an other terrestrial omnivores (Carlton and Hodder, active and focused search for possible evidence 2003), had an alternative option, namely to make of aquatic exploitation by early hominins. This use of aquatic resources provided by lowland study has put forward promising approaches and wetland areas. may trigger new research efforts in this direc- tion. Conclusions Acknowledgements The aim of our study is to provide ecological con- text for the current debate on modernity (or not) We owe thanks to Craig Feibel, whose work on of the use of aquatic resources by hominins. We fossil stingrays from the Turkana Basin inspired have used Early Pleistocene Trinil as a case study us to study the Javanese fossil stingray and its to investigate how questions on possible dietary aquatic context. Christine Hertler and Friedeman relevance of aquatic environments for early Schrenk kindly allowed us to borrow the stingray hominins can be addressed. At the time of depo- spines from Sangiran. We thank Simon Troel- sition of the Trinil HK sequence, the aquatic part stra (VUA) and Rob Moolenbeek (Zoological Mu- of the Trinil area contained rivers, lakes, swamp seum Amsterdam) for providing shells from the forests, lagoons and marshes with minor marine modern Solo river. Charles Barnard helped with influence, laterally grading into grasslands pos- processing the molluscan bulk samples. Thanks sibly subjected to regular inundation. It was, in also to Saskia Kars for making SEM photographs, terms of local environmental conditions and and to Gilles Cuny for giving his diagnosis on the faunal composition, comparable to the modern stingray stings. We are grateful to Gareth Davies tropical freshwater swamp forest biotope, which and Marin Waaijer for help with Sr isotopic mea- occurs along the lower reaches of tropical rivers surements, to Pieter Vroon for providing litera- and around tropical lakes. ture on Javan volcanics, and to Bert Boekschoten, The Trinil HK aquatic environment yielded Christine Hertler, Frank Huffman, Frits Muskiet aquatic food resources, including at least 11 ed- and Pat Shipman for their valuable comments ible mollusc species and four edible fish species on the manuscript. 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42 Son, V.D., 2003. Diet of Macaca fascicularis in a Dordrecht. mangrove forest, Vietnam. Laboratory Pri- Van Es, L.J.C., 1930. The prehistoric remains in mate Newsletter 42 (4): 1-6. Sampoeng Cave, Residency of Ponorogo, Java. Stewart, K.M., 1994. Early hominid utilisation of Proc. 4th Pac. Sc. Congr. 1929, 3: 329-340. fish resources and implications for seasonality Vonhof, H.B., Wesselingh, F.P., Ganssen, G.M., and behaviour. J. Hum. Evol. 27: 229-245. 1998. Reconstruction of the Miocene western Stewart, A.-M., Gordon, C.H., Wich, S.E., Schroor, Amazonia aquatic system using molluscan iso- P., Meijaard, E., 2008. Fishing in Macaca fascicu- topic signatures. Palaeogeogr., Palaeoclimatol., laris: a rarely observed innovative behavior. Palaeoecol.141: 58-93. Int. J. Primatol. 29: 543-548. Vonhof, H.B., Wesselingh, F.P., Kaandorp, R.J.G., Stringer, C. B., Finlayson, J.C., Barton, N.E., Davies, G.R., Van Hinte, J.E., Guerrero, J., Rae- Fernández-Jalvo, Y., Cáceres, I., Sabin, R.C., saenen, M., Romero-Pitmann, L., Ranzi, A., Rhodes, E.J., Currant, A.P., Rodriguez-Vidal, J., 2003. Paleogeography of Micocene western Giles-Pacheco, F., Riquelme-Cantal, J.A., 2008. Amazonia: isotopic composition of molluscan Neanderthal exploitation of marine mammals shells constrains the influence of marine in- in Gibraltar. Proc. Natl. Acad. Sci. 105 (38): cursions. Geol. Soc. Am. Bull. 115: 983-993. 14319-14324. Waselkov, G.A., 1987. Shellfish gathering and shell Sunquist, M., Sunquist, F., 2002. Wild cats of the midden archaeology. Advances in Archeologi- world. Chicago: University of Chicago Press. cal Method and Theory 10: 93-210. Swisher, C.C. III, Curtis, G.H., Jacob, T., Getty, A.J., Watanabe, N., Kadar, D. (Eds.), 1985. Quaternary Suprijo, A., Widiasmoro, 1994. Age of the earli- geology of the hominid fossil bearing forma- est known hominids in Java, Indonesia. Sci- tions in Java. Geological Research and Devel- ence 263(5150):1118-21. opment Centre Special Publication No. 4. Talwar, P.K., Jhingran, A.G., 1991. Inland fishes of Weesie, P.D.M., 1982. The fossil bird remains in India and adjacent countries. Volume 2. A.A. the Dubois Collection. Mod. Quaternary Res. Balkema, Rotterdam. SE Asia 7: 87-90. Ungar, P.S. (Ed.), 2007. Evolution of the human Whitford, D.J., 1975. Strontium isotopic studies of diet: the known, the unknown and the un- the volcanic rocks of the Sunda arc, Indonesia, knowable. Oxford University Press. and their petrogenetic implications. Geochim. Van Benthem Jutting, T. [W.W.S.], 1932. On pre- Cosmochim. Acta 39: 1287-1302. historic shells from Sampoeng Cave (Central Wood, B., Strait, D., 2004. Patterns of resource use Java). Treubia 14: 103-108. in early Homo and Paranthropus. J. Hum. Evol. Van Benthem Jutting, T. [W.W.S.], 1937. Non ma- 46: 119-162. rine mollusca from fossil horizons in Java with Wrangham, R.W., 2005. The delta hypothesis: special reference to the Trinil fauna. E.J. Brill, hominoid ecology and hominin origins. In: Leiden. Lieberman, D.E., Smith, R.J., Kelley, J. (Eds.), In- Van den Bergh, G.D, de Vos, J., Sondaar, Y., 2001. terpreting the past: essays on human, primate The Late Quaternary paleogeography of mam- and mammal evolution in honor of David Pil- mal evolution in the Indonesian Archipelago. beam. Brill Ac. Publ. Inc., Boston, pp. 231-242. Palaeogeogr., Palaeoclimatol., Palaeoecol. 171: Yang, S.L., 1990. Record of a freshwater bivalve, 385-408. Pseudodon vondembuschianus (Mollusca: Unio- Van Damme, D., 1984. The freshwater molluscs nidae) in Singapore. Raffles Bull. Zool. 38 (1): from northern Africa: distribution, biogeo- 83-84. graphy and palaeoecology. Junk Publishers,

43 44 2. Climatic and environmental reconstructions in the Turkana Basin: how useful are oxygen isotope ratios?

Josephine C.A. Joordens, Marlijn L. Noback, Hubert B. Vonhof, Craig S. Feibel, Dick Kroon

Abstract Introduction

Climate and environment are considered to be Climatic and environmental fluctuations on major factors influencing hominin evolution and orbital (precession, obliquity, and eccentricity) dispersal. In this study we test if oxygen isotope timescales have been invoked as important driv- ratios (δ18O) of fossil bivalve shells from ~2 mil- ers for hominin evolution and dispersal (deMeno- lion year old hominin-bearing sediments in the cal, 2004; Kingston, 2007; Potts, 2007; Trauth et Turkana Basin (Kenya, Ethiopia) can be used for al., 2007; Maslin and Trauth 2009). Specifically, reconstructing climate and environments in this factors associated with orbitally-forced seasonal- region. We show that seasonal shifts in δ18O val- ity may have provided key selective forces in the ues recorded by modern and fossil shells from evolution of the human lineage in Africa. Prin- the Turkana Basin are caused predominantly by cipal controls on the distribution of vegetation, wet-dry seasonal changes in host water chemis- and thus dietary resources and faunal commu- try, forced by summer monsoonal rainfall over nity ecology in this region, are the total annual the Ethiopian Highlands. Due to strong evapora- rainfall and the timing, duration and intensity of tion and dampening of the seasonal δ18O signal the dry seasons (Kingston, 2005). Hominin evo- in lakes, fossil shells from lake sediments are not lution and dispersal should therefore ideally be suitable for reconstruction of paleoclimate and evaluated within the context of changes in sea- paleoseasonality. In contrast, fossil shells from sonality over time. delta or river facies can be used for this purpose. The combination of δ18O and δ13C data from fossil Of particular interest is the time period about 2 shells in the Turkana Basin allows distinction be- million years ago (Ma), when a hominin fauna tween lake, delta (river plume) and river paleoen- including two early Homo species and Paran- vironments. thropus robustus was present in the lacustrine Turkana Basin of Kenya and Ethiopia (Feibel et The presence of large fossil bivalve shells in the al., 1989; Fig. 1). Between ~2-1.6 Ma, the Turkana paleolake indicates that alkalinity in the Turkana Basin held a large lake (Lake Lorenyang) with the Basin at ~2 Ma must have been lower than today, paleo-Omo River from the N as its main (~ 90%) despite the concomitant lacustrine δ18O values of water source and smaller rivers from the SW as ~ +6 ‰ that are similar those in the present-day minor water sources (Feibel et al., 1991). Climatic highly alkaline Lake Turkana. This can be ex- control in the region is, and likely was in the plained by the non-linear response of lake water past ~ 4 My, dramatically partitioned: a hot arid δ18O to increasing evaporation (Craig-Gordon to semi-arid climate reigns in the sedimentary model). Environmental conditions in the paleo- part of the Turkana Basin, while the Ethiopian lake at ~ 2 Ma were more favorable than those Highlands -drainage area of the Omo River- are in the modern Lake Turkana: it provided good warm temperate to tropical with strong summer drinking water and abundant aquatic molluscs, monsoonal rainfall (Feibel, 1999). Seasonality in fish and other aquatic animals (crocodiles, tur- Equatorial Africa is (and was during the past mil- tles, hippos) as a possible hominin food supply. lions of years) primarily expressed as monsoonal rainfall variation which determines strong sea- 45 Figure 1 (left). Map of the Turkana Basin with the Omo delta, Turkwel and Kerio Rivers and the location of Sanderson’s Gulf. Sampling areas (Area 102, 100, 123) indicated with asterisks.

Kibish Lower Omo Valley

Shungura

Omo R. Sanderson’s Gulf

Todenyang Facies (shell) ~1.87 Ma KBS Tuff

Ileret Nariokotome llia Il A C3 Delta (KJ04-28)

Kangaki Lomekwi Koobi Fora upper Burgi * Region Member Turkana * Il L taboi Region a okochot K Lake Turkana C2 Lake (KJ04-53, KJ06-32)

Kalakol C1 Lake (KJ04-38)

Lake (KJ04-44) Lodwar Turkwel R. Gus ~2 Ma Lowa- sera

Loiyan- galani Figure 2 (top). Composite stratigraphy of the upper Burgi Member (early Lake Lorenyang) between the unconformity at ~ 2 Ma and the KBS Tuff at 1.869 +/- 0.021 Ma io R. (McDougall and Brown 2006, 2008) with regional marker Ker beds C1, C2 and C3. Red ellipses indicate stratigraphical level where fossil bivalve shells were sampled. All fossil

Suguta Depression shells were sampled from lake facies, except for KJ04-28 that derives from delta facies.

sonal variation in Omo River discharge into the paleoclimate over time, and specifically, to recon- Turkana Basin, as well as the local evaporation- struct changes in paleoseasonality. precipitation balance. This is reflected in oxygen isotope (δ18O) variation of Turkana Basin lake To this end, we analyzed stable (oxygen and car- waters, with lowest δ18O values corresponding to bon) isotope ratios of successive growth incre- peak river discharge and low evaporation. Sea- ments from chemically well-preserved aragonitic sonal variation in water oxygen isotope signals is freshwater bivalve shells sampled from several captured at high temporal resolution in growth stratigraphic levels of the upper Burgi (UBU) incremental records of freshwater molluscan Member in the E Turkana Basin (Fig. 2). To place shells, as shown by studies of modern and fos- the fossil shell δ18O values in a known climatic sil shell material (Abell et al., 1996; Rodrigues and environmental context, we sampled and et al., 2000; Hailemichael et al., 2002; Kaandorp analyzed oxygen isotope ratios of present-day et al., 2003; Kaandorp et al., 2006; Versteegh et Lake Turkana, Turkwel River and Omo River delta al., 2010a; Versteegh et al., 2010b). In this study, waters. Due to its high alkalinity of ~ 20-23 meq/l we aim to test whether δ18O of fossil shells from (Cerling, 1979), modern Lake Turkana has a very hominin-bearing sediments in the Turkana Basin limited molluscan fauna consisting of stunted can be used to reconstruct changes in regional and thin-shelled specimens (Cohen, 1986; Van 46 Shell growth direction 1

Shell growth direction 2

Umbo

Location of section with longest growth Ventral margin axis

Figure 3. Schematic drawing of a bivalve shell, showing the location where the thin section for growth incremental analy- sis is cut. Rectangle: location of sampling in most shell specimens. Adapted from Carré et al. (2006).

Damme and Van Bocxlaer, 2009), lacking large lected from deltaic sediments. To assess the pos- bivalves suitable for growth incremental isotope sible impact of diagenesis on preservation and analysis. However, it was possible to analyze re- δ18O values of the fossil shells, a fossil Etheria shell cent shells from the Omo River and from the rela- (KJ06-21) that visually appears altered by diagen- tively fresh Sanderson’s Gulf in the SW corner of esis was included in the analysis. To investigate Lake Turkana, close to the Omo delta (Fig. 1). the level of diagenetic alteration and its potential influence on the oxygen isotopic signal, we per- Methods formed Scanning Electron Microscopy (SEM) on all shell specimens. Small fragments of shell ma- Sample collection – In total, eight unionid bivalve terial were placed on a stub and coated with gold. shells were selected for oxygen isotope analysis Scanning electron microscopy pictures where of growth increments (Table 1, Fig 1). The recent taken of all fragments at 10 and 1 μm scales. Omo River shell (river oyster, Etheria elliptica) was Water samples for oxygen isotope analysis were collected in 2003 by F.H. Brown in Ethiopia, at N collected from Lake Turkana (SE shore, E shore, 05º.41’ E 35º.91’. The shell from Sanderson’s Gulf Ferguson’s Gulf at the W shore), the Omo River (Chambardia wahlbergi) was collected in 1968, and Delta and the Turkwel River in the SW Turkana has been provided by D. van Damme. Five large Basin (Table 2). Water was sampled from clean fossil bivalve shells from paleolake Lorenyang surface water using a plastic syringe, which was were collected by the authors in 2004 and 2006 emptied over a Millipore filter into a glass bottle. from stratigraphically well-constrained levels The bottle was filled to overflow and then closed in the upper Burgi Member on the Koobi Fora with a screw cap. Ridge (Area 100 and 102) and in the Bura Hasuma region E of present-day Lake Turkana (Area 123; Stable isotope analysis – The shells selected for Fig. 1). All fossil shells derive from lake sediments growth incremental sampling (Table 1) were except for one shell (KJ04-28) that has been col- embedded in epoxy resin. Sections of ~0.3 mm 47 Figure 4. Thin sections of six bivalves subjected to growth incremental analysis. Black lines indicate the sampled area, numbers indicating first and last (ontogenetically youngest) sample number. Scale bars are 1 cm. A: FB2003Omo, mod- ern Etheria elliptica from the Omo River. B: KJ04-38.2, fossil Coelatura sp. From C1-20 m. C: KJ04-44.1, fossil Iridina omoensis from C1-20 m. D: SanGulf1968, modern Chambardia wahlbergi from Sanderson’s Gulf in Lake Turkana. E: KJ04-53.1, fossil Pleiodon bentoni from C2. F: KJ04-28, fossil Iridina omoensis from C3. Species names according to Van Bocxlaer and van Damme 2009. 48 Sample name Location Strat. level Species name

FB2003Omo Omo River Recent (2003) Etheria elliptica SanGulf1968 Sanderson’s Gulf Recent (1968) Chambardia wahlbergi KJ04-28 Area 102 UBU, C3 Iridina omoensis KJ06-32 Area 123 UBU, C2 Iridina omoensis KJ04-53.1 Area 102 UBU, C2 Pleiodon bentoni KJ04-38.2 Area 100 UBU, C1-5.3 m Iridina omoensis KJ04-44.1 Area 100 UBU, C1-20m Coelatura sp. KJ06-21 Area 102 KBS, A1 Etheria elliptica

Table 1. Overview of molluscan shells used in the growth incremental analysis. KFR = Koobi Fora Ridge, BH = Bura Hasuma. KBS = KBS Member (above UBU), UBU = upper Burgi Member. Species names following Van Bocxlaer and van Damme (2009).

Sample name Location Sample date δ18O (‰ VPDB)

KWJ06-1 SE shore Lake Turkana 26 July 2006 +6.39 KWJ06-2 Koobi Fora spit 6 August 2006 +5.84 KWJ06-3 Koobi Fora spit, during 7 August 2006 +5.57 local rain shower KWJ06-4 Lugga during local rain shower (Area 102) 7 August 2006 -0.88 KWJ06-5 Lugga during local rain shower (Area 102) 7 August 2006 -2.92 Omo 1 Omo River delta 12 August 2004 -2.35 N 4°35.388’ E 36°02.247’ (peak flooding) 09JJ-2 Turkwel River at TBI Field station January 2009 +0.55 09JJ-1 Borehole TBI Turkwel January 2009 -0.83 09JJ-3 Ferguson’s Gulf January 2009 +7.21 09JJ-4 Ferguson’s Gulf January 2009 +6.95

Table 2. Oxygen isotope ratios measured in water samples from several locations around Lake Turkana, the Omo River delta, Turkwel river, and ephemeral streams (“lugga”) fed by an unexpected heavy local rain shower. TBI: Turkana Basin Institute.

Environment/Facies Shell sample Range (‰) δ18O shell Range (‰) δ18Owater

River (floodplain?) FB2003Omo -2.5 to +0.3 -0.9 to +1.8 Lake near delta SanGulf1968 -3.5 to +2.8 -1.9 to +4.4 Lake KJ04-38 +3.0 to +4.5 +4.6 to +6.1 Lake KJ04-44 +3.0 to +4.5 +4.6 to +6.1 Lake KJ04-32 +3.0 to +4.5 +4.6 to +6.1 Lake KJ06-53 +3.0 to +4.5 +4.6 to +6.1 River delta KJ04-28 -4.0 to -1.5 -2.4 to +0.1

Table 3. Measured range in shell δ18O values (bold) and calculated range in host water δ18O values (Dettman et al. 1999; Gonfiantini et al. 1995; Grossman and Ku 1986). thickness were cut along the longest growth axis tory in Amsterdam, either on a Thermo Finnigan of the bivalve (Fig. 3). Growth increments in the MAT 252 mass spectrometer with an automated nacreous layer of the shells (Fig. 4, 5) were sam- carbonate extraction line (Kiel-II device), or on pled with a Merchantek MicroMill microsampler, a Thermo Finnigan Delta+ mass spectrometer using a drill bit with ~100 μm drill tip diameter. with a Gasbench-II preparation device. On both Depending on the width of the shell section, ap- systems the long-term standard deviation of a proximately 40 to 100 samples (sample spacing routinely analysed in-house CaCO3 standard was 18 13 ~ 100-150 μm, drilling depth ~ 250 μm) per bi- < 1 ‰ for both δ O and δ C values. This CaC03 valve were taken. Each drilled growth increment standard is regularly calibrated to NBS 18, 19 and powder was collected separately in a small glass 20. Both δ18O and δ13C values of shell aragonite container. Stable isotope (δ18O and δ13C) meas- are reported relative to Vienna-Peedee belem- urements on shell aragonite powders were per- nite (VPDB). Water samples were analyzed for formed at the FALW-VUA stable isotope labora- δ18O at the FALW-VUA stable isotope laboratory 49 Figure 5. Thin section of Etheria elliptica (KJ06-21) used for diagenesis testing. The rectangle indicates area with still visible growth lines (15 samples taken). The three black lines indicate position of three samples taken in area with crystal growth. Scale bar is 1 cm. on a Thermo Finnigan Delta+ mass spectrometer Past water temperature is estimated based on equipped with a Gasbench-II. Water δ18O is re- modern values for water temperature in Lake ported in ‰ relative to Vienna Standard Mean Turkana. Annual surface water temperature Ocean Water (VSMOW). The long-term standard variations in present-day Lake Turkana are deviation of a routinely analysed in-house water very small, ranging between 27.5 and 29.5 ºC standard is < 0.1 ‰ for δ18O. (Hopson,1982). Since the Turkana Basin is in an equatorial setting with persistently high air tem- Based on measured oxygen isotope values of fos- peratures similar to those today over the past 4 18 sil and modern shell aragonite (δ Oar), oxygen My (Passey et al., 2010), we use an assumed con- 18 isotope values of host waters (d Ow) were cal- stant average water temperature of 28.5ºC (301.65 18 culated by applying the equation for biogenic degrees Kelvin) in the calculations of δ Ow (VS- aragonite (Dettman et al., 1999; Grossman and MOW). Ku, 1986): Results 1000 ln α = 2.559 (106T-2) + 0.175 (1) Diagenetic analysis – The modern shells from Omo where T is the water temperature in degrees Kel- River and Sanderson’s Gulf both show the char- vin and α is the fractionation between water and acteristic pattern of lamellar aragonite crystals aragonite described by: with clear and sharp boundaries between crystals (Fig. 6A, B). The fossil shells also have lamellar 18 α = (1000 + δ Oar (VSMOW) (2) aragonite crystals, with no sign of recrystalliza- 18 (1000 + δ Ow (VSMOW) tion or formation of other crystals than aragonite (Fig. 6C-F). The structure of the aragonite dis- 18 18 To convert measured δ Oar (VPDB) to δ Oar (VS- plays traces of minor dissolution along minuscule MOW), the following equation (Gonfiantini et al., cracks that run through the crystal (Fig. 6D). The 1995) is used: aragonite crystals are slightly rounded at the corners and boundaries between crystals are less 18 18 δ Oar (VSMOW) = 1.03091 (1000 + δ Oar (VPDB)) – sharp than those in modern shells (Fig. 6E-F). 1000 (3) Shell KJ06-21 (Etheria elliptica; Fig. 6G-H) shows both severe dissolution and recrystallization,

Figure 6 (right). SEM photos. A. Lamellar aragonite layers of FB2003Omo, modern Etheria elliptica from the Omo River. B: Detail of the aragonite crystals of FB2003Omo. C: Lamellar aragonite layers of KJ04-28, fossil Iridina omoensis from C3. D: Minor cracks in aragonite crystals of KJ04-53.1, fossil Pleiodon bentoni from C2. E: Rounded aragonite crystals with blurred borders, in KJ04-53.1. F: Detail of borders between aragonite crystals of KJ04-53.1. G: Dissolution and recrystallization in KJ06-21, fossil Etheria elliptica from A1. H: Detail of dissolution and recrystallization in KJ06-21. 50 51 confirming its diagenetic alteration. Based on +1.8 ‰. these results, we conclude that the fossil shells -except KJ06-21- are chemically well-preserved Water samples – The δ18O values of water samples and will reflect the original stable isotope com- are presented in Table 2. Measured values in per- position. manent water bodies range from -2.35 ‰ in the Omo River delta to +7.21 ‰ in Ferguson’s Gulf at Stable isotope ratios of modern and fossil bivalve the western side of Lake Turkana. Values meas- shells – Stable isotope ratios of fossil and mod- ured at the Koobi Fora shoreline ranged from ern shells are presented in Figures 7- 9. The +5.5 to +5.8 ‰. Further to the South, at a greater δ18O values measured in growth increments of distance from the Omo Delta, a δ18O value of +6.39 the modern Omo River shell (Fig. 7A) show two ‰ was measured at the SE shore. The elevated cycles with amplitude of ~3 ‰. The δ18O values δ18O values at a greater distance from the Omo range between -2.5 and + 0.5 ‰. The δ18O values River delta, and in restricted areas such as Fergu- of the modern shell from Sanderson’s Gulf (Fig. son’s Gulf, reflect an evaporation trend. During a 7B) range from -3.5 to +3 ‰. After a juvenile pe- freak heavy rain shower on 7 August 2006 we had riod characterized by low values follows a period the opportunity to sample water from rapidly with increasing δ18O, and another period with flooding “luggas” (ephemeral streams, normally low values. Two fossil shells deriving from lake dry in August) in Area 102. In one that consisted sediments below level C1 show cyclicity with a of freshly falling rainwater, we measured a δ18O relatively small amplitude of ~0.5 to 1.5 ‰ (Fig. value of -2.95 ‰. 8A, B). The δ18O values range from +3.5 to +4.5 ‰. The two fossil shells from lake sediments at level Discussion C2 show a similar pattern (Fig. 8C, D). Lastly, δ18O of the fossil shell from level C3 has amplitude of Seasonal changes in O isotope ratios of modern shells ~ 2 ‰, with values ranging between -4 and -2 ‰ – The oxygen isotopic composition of freshwater (Fig. 8E). This is the only well-preserved fossil bivalves is generally in equilibrium with ambi- shell with low oxygen isotope values, all other ent water and is influenced by δ18O of water and fossil shells are characterized by high isotope val- by temperature (Dettman et al., 1999; Kaandorp ues. The δ18O values of the diagenetically altered et al., 2003; Gajurel et al., 2006; Goewert et al., fossil oyster KJ06-21 range from -6 to -4 ‰, with 2007). At high latitudes, strong seasonal shifts in no sign of cyclicity in the signal. The δ13C values water temperature (up to 27 ºC (Versteegh, 2009)) range between -9 and -9.5 ‰ (Fig. 9). The low δ18O have profound effects on fractionation of oxy- values match with the composition of modern lo- gen isotopes (Gat, 1996). In contrast, due to the cal rainfall (-6 to 0 ‰ (I.A.E.A./WMO, 2006)), con- low-latitude equatorial setting of the Turkana firming findings that recrystallization depletes Basin and its drainage area, seasonal variation in δ18O values in coquinas from Koobi Fora (Cerling water temperature is low (~ 2 ºC (Hopson, 1982)) et al., 1988). and shell δ18O composition is expected to mainly reflect host water chemistry. To test this, we dis- When δ18O values of all shells are plotted in an cuss the stable isotope composition of the mod- overview chart (Fig. 10), a low-value (~ -3 ‰) ern shells of Omo River and Sanderson’s Gulf in cluster is situated at the bottom of the chart and the light of their environmental context. a high-value cluster (~ +3 ‰) at the top of the chart. The low-value cluster contains the modern The Omo River shell FB2003Omo shows an av- 18 Omo River shell and the fossil paleodelta (level erage δ O value of -1.6 ‰ and a cyclical range C3) shell. The high-value cluster contains the in values between -2.5 and +0.5 ‰ (Fig. 7A). If fossil shells that derive from lake sediments. The equilibrium precipitation of shell carbonate with recent shell from Sanderson’s Gulf near the Omo Omo River water is assumed, and if oxygen iso- delta alternates over time between the two clus- tope ratios were solely an effect of temperature, ters. Calculated water δ18O values (Fig. 10; Table the ~3‰ amplitude would mean a seasonal range 3) indicate that the high-value cluster derives in water temperatures of ~12 °C which is unreal- from waters with a δ18O value of ~ +4.6 to +6.1 ‰, istic for an equatorial region. Thus, water tem- while the low-value cluster derives from water perature alone cannot explain the observed cycli- with a calculated range in δ18O values of -2.4 to cal shift in shell δ18O values. Water chemistry of 52

Figure 7A Figure 7A

Figure 8A

Figure 8A

juvenile adult juvenile adult juvenile adult juvenile adult

A A

Figure 8B

Figure 7B Figure 8B Figure 7B

juvenile adult

juvenile adult B B

6 Figure 7. Oxygen and carbon isotope ratios. A: Recent Figure 8AB. Oxygen and carbon isotope ratios. A: Fossil shell FB2003Omo from the Omo River. B: Recent shell shell KJ04-38.2 from lake facies, C1-5.3 m. B: Fossil shell SanGulf1986 from Sanderson’s Gulf. KJ04-44.1 from lake facies, C1-20 m. 6 the Omo River changes on seasonal timescales: in δ18O cyclicity in the modern Omo shell (Fig. 7A) the wet season between May and October, strong is caused predominantly by wet-dry7 seasonal monsoonal rainfall feeds the river with rainwa- changes in host water chemistry.7 ter characterized by depleted δ18O values (-2.8 ‰ (I.A.E.A./WMO 2006); -2.95 ‰, Table 2). Low The stable isotope profi le of the modern Cham- δ18O values in the Omo River shell thus refl ect bardia wahlbergi shell (SanGulf1968) from Sander- the wet season in Ethiopia, while high values re- son’s Gulf (Fig. 7B) requires a detailed interpre- fl ect the dry season. Assuming a constant water tation because of the complex environmental temperature of 28.5 ºC, the measured δ18O values conditions at its collection site. Depending on of the modern Omo shell yield calculated water variable rainfall and lake levels over the years, 18 δ Ow values ranging from -0.9 to +1.8 ‰ (Table 3). Sanderson’s Gulf can be a completely dry area Ricketts & Johnson (Ricketts and Johnson, 1996) or a shallow water area connected to the larger 18 measured Omo River water δ Ow values of -1.2 to lake (Butzer and Kirchner, 1971). During part or 18 -0.1 ‰. We measured a δ Ow value of -2.35 ‰ in all of the SanGulf1968 mollusc’s lifetime, Sander- water from the Omo River delta at peak fl ooding son’s Gulf probably was a shallow gulf or fl ood- during the summer monsoon (Table 2). The rela- plain connected to Lake Turkana (Van Damme 18 tively high calculated δ Ow values (up to +1.8 ‰) and Van Bocxlaer, 2009). Due to its proximity to suggest that FB2003Omo lived in the fl oodplain the Omo River delta, Sanderson’s Gulf received area of the Omo River where dry season evapora- suffi cient freshwater input to permit growth of tion caused some enrichment of the water oxy- large healthy bivalves. In the juvenile stage of gen isotope ratios. We conclude that observed SanGulf1968, δ18O values of shell aragonite are 53

Figure 8E Figure 8C

Figure 8C

C E

FigureFigure 88D. Oxygen and carbon isotope ratios. A. Fossil shell KJ04-38.2 from lake facies, C1-5.3 m. Figure 8D B. Fossil shell KJ04-44.1 from lake facies, C1-20 m. C. Fossil shell KJ04-53.1 from lake facies, C2.

D. Fossil shell KJ06-32 from lake facies, C2. E. Fossil shell KJ04-28 from delta facies, C3.

Figure 8CDE. C: Fossil shell KJ04-53.1 from lake facies, C2. D: Fossil shell KJ06-32 from lake facies, C2. E: Fossil D shell KJ04-28 from delta facies, C3.

low and similar to those of the Omo River shell. delta facies (-3 ‰) is considerable: ~ 7 ‰. This As the shell grows its δ18O values increase, likely does not necessarily refl ect a diff erence in cli- refl ecting increasing evaporation of the Sander- mate, but is most likely predominantly caused son’s Gulf water and absence of Omo River water by a diff erence in local environment. Especially infl ow. This is followed by an abrupt return to in shallow, stagnant parts of an equatorial lake, 18 low δ O values, likely refl ecting8 8 renewed infl ow evaporation can result in rapid strong enrich- 18 18 of Omo River water into Sanderson’s Gulf. This ment of water δ O values, and 9thus δ O values of pattern can be interpreted as representing a sea- shells growing in this environment. The increase sonal signal, with high δ18O values representing of δ18O values, as recorded in the modern shell the dry season and low values the wet summer from Sanderson’s Gulf, illustrates this evapora- monsoon season. tion process. In a delta or river, the steady sup- ply of running water characterized by low δ18O Facies-related diff erence in O and C isotope ratios of values, results in molluscan shells with low δ18O fossil shells – Because of the equatorial position of values. High river discharge due to summer mon- the Turkana Basin and its long-lived riverine con- soonal rainfall brings water with more depleted nection to the Ethiopian Highlands (Feibel, 1999), δ18O values, tending towards rainfall δ18O values. we interpret δ18O values in the fossils shells (Fig. This situation is refl ected in shell KJ04-28 from 8) in the same way as those in the modern shells. C3, which derives from the delta of the paleo- Hence, observed cycles of alternating high and Omo River that migrated southward along the 18 low δ O values of shell aragonite are considered eastern paleolake margin and “arrived” in Area to be seasonal cycles, with maximum δ18O cor- 102 at the time of deposition of marker bed C3 responding to the dry season and minimum δ18O (Feibel, 1988). The oxygen isotope record of the to the summer monsoon wet season in the Ethio- shell shows fi ve wet periods and fi ve dry periods pian Highlands. (Fig. 8E). In the juvenile phase, rapid growth is expected to record relatively more detail than The absolute diff erence in average 18δ O values of later on when growth rates decrease (Morris and fossil shells sampled from lacustrine facies (~ +4 Corkum, 1999). Hence, in the juvenile period peak ‰) and a fossil shell KJ04-28 from C3 sampled in shape is better resolved than in its adult period. 54 Figure 9. Stable isotope ratios of growth increments from fossil “test” oyster KJ06-21. Triangles indicate samples from visually recrys- tallized (diagenetic, calcitic) areas. Dots indicate samples taken in visually recogniz- able growth increments.

Figure 9. Stable isotope ratios of growth increments from fossil “test” oyster KJ06-21. Triangles indicate samples from visually recrystallized (diagenetic, calcitic) areas. Dots indicate samples taken in visually recognizable growth increments.

Figure 10. Measured range in shell δ18O values (bold) and calculated range in host water δ18O values (Dettman et al., 1999; Gonfi antini et al., 1995; Grossman and Ku, 1986).

Figure 10. Overview of δ18O values of all fossil and modern shells (left axis). Calculated δ18O of (paleo)waterThe range (Dettman in measured et al. 1999; Gonfiantinishell δ18 Oet al.values 1995; G ofrossman KJ04- and Ku 1986)ronmental is presented setting. on Monitoring studies on mod- 18 the28 right results axis. in calculated water δ Ow values rang- ern bivalve shells in S America have shown that ing from -2.4 to 0.1 ‰. This agrees well with the oxygen isotope signals in bivalve shells from a range of values measured in the Omo River. The lake, where surface water residence time exceeds 18 lowest δ Ow value (-2.35 ‰; Table 2) was meas- a seasonal cycle, tend to be dampened compared ured in the delta during peak fl ooding of the Omo to bivalves living in the river that feeds the lake River in 2004; higher values (-1.2 to -0.1 ‰)10 were (Kaandorp et al., 2006). Hence, although the measured in the Omo River (Ricketts and John- Lake Lorenyang bivalves from lacustrine facies son, 1996). do record seasonal cyclicity, this signal is heav- Seasonal cyclicity of δ18O values in the fossil ily overprinted by the environmental setting. shells is, with exception of shell KJ04-28, much We conclude that both absolute values of and less pronounced than cyclicity in the modern amplitude in ranges of δ18O values of fossil shells Omo River shell. Although this could be inter- from lake sediments are not suitable as indica- preted as the result of a smaller diff erence be- tors of seasonality. In contrast, fossil shells from tween wet and dry seasons (lower seasonality) river or delta sediments (e.g. KJ04-28) appear to during these time periods, the smaller11 amplitude be more reliable indicators of seasonality. The is more likely the result of a diff erence in envi- amplitude of the wet-dry seasonal cycles in the 55 stable isotope values Modern shells 6

5 A Omo River lake 4 Sanderson’s Gulf 3 modern ostracods

2

1 river

O (VPDB) 0 18 δ -1 river plume or delta -2

-3

-4 -20 -15 -10 -5 0 5 10 δ13C (PDB)

stable isotope values Lorenyang shells 6 44.3 44.1 5 B 28C3-2 38.2 lake 4 62B 53.1 3

2

1 river

O (VPDB) 0 18

δ river plume -1 or delta -2

-3

-4 -20 -15 -10 -5 0 5 10 δ13C (PDB)

Figure 11. A. Stable isotope values of Modern shells and ostracods: oxygen isotope ratios versus carbon isotope ratios. Three data clusters can be distinguished, representing three (paleo-)environments: river, river plume (or delta) and lake. The shell from Sanderson’s Gulf reflects alternation between river plume (delta) and lake conditions, as a result of proximity of the Omo River delta. B. Stable isotope values of fossil shells from the upper Burgi Member: oxygen versus carbon isotope ratios. All fossil shells fall in the lake cluster, except KJ04-28 from level C3 that matches with the river plume (or delta) cluster. fossil shell KJ04-28 from delta deposits is ~2.5 ‰, period ~ 3.9 Ma in the Turkana Basin (Macho et comparable to the amplitude of cycles recorded al., 2003). However, it cannot be excluded that the in the modern Omo River shell. This suggests that amplitude between peaks and lows in KJ04-28 is seasonality at ~ 1.9 Ma was similar to seasonal- somewhat dampened because it derives from a ity today, as was previously found for the time delta rather than a river (Kaandorp et al., 2006). 56 Lake Lorenyang Lake Turkana ~ 6 ‰

Figure 12. Conceptual diagram illustrating the 18 non-linear relation between δ18O and alkalin- O ity in waters of the Turkana Basin, according to the Craig-Gordon model of evaporative enrich- Omo River ment. Dashed line indicates the plateau value in δ18O, resulting from back-condensation of δ18O-depleted atmospheric water vapour Alkalinity 16 23 Meq/l (Craig and Gordon, 1965).

Carbon isotope ratios – The carbon isotope ratios is: does this mean that alkalinity in Lake Loren- (δ13C) of fossil and modern shells (Figs. 7-9) also yang was similar to alkalinity in present-day Lake show cyclicity which may be related to wet-dry Turkana? It is important to assess the relation seasonality. For instance in the modern Omo Riv- between δ18O values and alkalinity of paleolake er shell, δ18O and δ13C vary in anti-phase, while in waters, since alkalinity strongly influences the the shell from Sanderson’s Gulf δ18O and δ13C vary availability of drinking water for terrestrial fauna in phase. However, the exact causes of the ob- (Cerling, 1979). served carbon isotope signal in freshwater shell aragonite remain difficult to resolve (Kaandorp In a study on oxygen isotope ratios of evaporat- et al. 2006; Versteegh, 2009). When δ18O values ing brines in an Indian lake, it was shown that of Modern shells and ostracods from different progressive evaporation of saline-alkaline lake known environments in the Turkana Basin are water resulted in a steep linear increase of δ18O plotted against their δ13C values, three clusters values and total salt content (including alkalin- of values can be distinguished (Fig. 11A). A lake ity), up to a point where total salt content contin- cluster characterized by high δ18O and δ13C val- ued to increase but δ18O reached a plateau value ues, a river cluster with low δ18O and δ13C values, as a result of back-condensation of δ18O-depleted and an intermediate cluster (Sanderson’s Gulf) atmospheric water vapour as predicted by the that can be interpreted as reflecting delta (river Craig-Gordon model for evaporative δ18O enrich- plume) conditions. When the fossil shells are ment (Craig and Gordon, 1965; Yadav, 1997). We plotted in the same way, all shells fall in the lake expect that a similar mechanism underlies the cluster, except for KJ04-28 from C3 which falls relation between δ18O and alkalinity in both an- in the delta (river plume) cluster. It appears that cient and modern lakes in the Turkana Basin. At none of the fossil shells derives from a riverine values >16 meq/l, the concentration of Ca ions setting (Fig 11B). in lake water falls below 6 ppm due to precipita- tion (Cerling, 1979), and bivalve shell calcium The relation between oxygen isotope ratios and alka- carbonate can no longer be formed. The presence linity – The water of present-day Lake Turkana of large fossil bivalve shells in the UBU deposits has a high alkalinity of 20-23 meq/l (Cerling demonstrates that alkalinity at that time must 1979) and oxygen isotope ratios vary between have been <16 meq/l, despite the concomitant +5.5 to +7.2 ‰ (this study, Table 2). The highest (calculated) paleolake δ18O values of ~ +6 ‰. δ18O values calculated for water of Lake Loren- Hence, we infer that the lake water δ18O of ~ +6 ‰ yang (~ +6.1 ‰, Table 3) fall within the range of already represents the plateau value that can re- modern Lake Turkana δ18O values. The question late to a wide range of alkalinity values (Fig. 12). 57 Conclusions Acknowledgments

Selected fossil bivalve shells from the upper This study was supported by the Netherlands Burgi Member still preserve the original stable Organisation for Scientific Research (NWO). We isotope signal that represents their growth envi- thank Kamoya Kimeu, Ndolo Muthoka, Muthoka ronment. Seasonal shifts in δ18O values recorded Kivingo, Halewijn Scheuerman†, the Koobi Fora by the modern and fossil shells from the Turkana Research Project and the Turkana Basin Insti- Basin are caused predominantly by wet-dry sea- tute for logistical support in the field. We are sonal changes in host water chemistry caused by grateful to Frank Brown and Dirk van Damme monsoonal rainfall over the Ethiopian Highlands. for providing key shell specimens, and to Louise Average δ18O values differ considerably between Leakey and Ikal Angelei for water sampling at the the analyzed shells, which is facies-related and West side of Lake Turkana. Furthermore, we owe not climate-related: shells from river and delta thanks to Wynanda Koot and Suzanne Verdegaal sediments have low δ18O values while shells from for analytical assistance, to Saskia Kars for mak- lake sediments have high δ18O values due to evap- ing the beautiful SEM and other photographs, oration of lake waters. and to Emma Versteegh and Jeroen van der Lub- be for valuable comments on the manuscript. We All analyzed shells, fossil and recent, show al- gratefully acknowledge the National Museums of ternation between dry and wet seasons, but the Kenya and the Government of Kenya for facilitat- amplitude in δ18O values of shells from paleolake ing our research in the Koobi Fora region. facies is considerably smaller than that of river and delta shells. The dampening of the seasonal References δ18O amplitude is typical for lacustrine shells, due to the fact that water residence time in lakes ex- Abell, P.I., Amegashitsi, L., Ochumba, P.B.O., 1996. ceeds a seasonal cycle (Kaandorp et al. 2006). Fos- The shells of Etheria elliptica as recorders of sil shells from Turkana Basin lake sediments are seasonality at Lake Victoria. Palaeogeography, therefore not suitable for reconstruction of pa- Palaeoclimatology, Palaeoecology 119 (3-4): leoclimate and paleoseasonality. In contrast, fos- 215-219. sil shells from delta or preferably river facies can Braun, D.R., Harris, J.W.K., Levin, N.E., McCoy, be used for paleoclimate and paleoseasonality J.T., Herries, A.I.R., Bamford, M.K., Bishop, reconstruction. The combination of δ18O and δ13C L.C., Richmond, B.G., Kibunjia, M., 2010. Early data from fossil shells in the Turkana Basin can hominin diet included diverse terrestrial and be used to distinguish lake, delta (river plume) aquatic animals 1.95 Ma in East Turkana, Ken- and river paleoenvironments. The presence ya. Proceedings of the National Academy of of large fossil bivalve shells in the upper Burgi Sciences of the United States of America 107 Member indicates that alkalinity of Lake Lore- (22): 10002-10007. nyang must have been < 16 meq/l at that time Butzer, K.W., Kirchner, J.A., 1971. Recent History (Cerling, 1979), despite similar high δ18O values of an Ethiopian Delta: The Omo River and the in paleolake water and modern lake water. The Level of Lake Rudolf. University of Chicago, latter observation can be explained by the Craig- Dept. of Geography. Gordon model, with a non-linear response of Cerling, T.E., 1979. Paleochemistry of Plio-Pleis- lake water δ18O to increasing evaporation (Craig tocene lake Turkana, Kenya. Palaeogeography, and Gordon, 1965). An alkalinity of < 16 meq/l in Palaeoclimatology, Palaeoecology 27: 247-285. the upper Burgi Member (early Lake Lorenyang) Cerling, T.E., Bowman, J.R., Oneil, J.R., 1988. An means that the paleolake in this time period isotopic study of a fluvial-lacustrine sequence could provide good drinking water and abundant - the Plio-Pleistocene Koobi Fora sequence, aquatic molluscs, fish and other aquatic animals East Africa. Palaeogeography, Palaeoclimatol- (crocodile, turtle) as a possible hominin food ogy, Palaeoecology 63 (4): 335-356. supply (Cerling, 1979; Braun et al., 2010). Hence, Cohen, A.S., 1986. Distribution and faunal asso- environmental conditions in the Turkana Basin ciations of benthic invertebrates at Lake Tur- during early Lake Lorenyang times were more kana, Kenya. Hydrobiologia 141 (3): 179-197. favorable for hominins than those in the modern Craig, H., Gordon, L.I., 1965. Deuterium and oxy- Lake Turkana area. gen 18 variations in the ocean and the marine 58 atmosphere. In: Tongiorgi, E. (ed), Stable iso- bon isotope fractionation in biogenic arago- topes in oceanographic studies and paleotem- nite: temperature effects. Chemical Geology peratures. Laboratoria di Geologia Nucleare, 59:59-74. Pisa, pp 9-130. Hailemichael, M., Aronson, J.L., Savin, S., Tevesz, deMenocal, P.B., 2004. African climate change and M.J.S., Carter, J.G., 2002. Delta 18-O in mollusk faunal evolution during the Pliocene-Pleisto- shells from Pliocene Lake Hadar and modern cene. Earth and Planetary Science Letters 220 Ethiopian lakes: implications for history of the (1-2): 3-24. Ethiopian monsoon. Palaeogeography, Palaeo- Dettman, D.L., Reische, A.K., Lohmann, K.C., 1999. climatology, Palaeoecology 186 (1-2): 81-99. Controls on the stable isotope composition Hopson, A.J. (ed), 1982. Lake Turkana. A report of seasonal growth bands in aragonitic fresh- on the findings of the Lake Turkana project water bivalves (Unionidae). Geochimica et 1972-1975, Vols 1-6. UK Overseas Development Cosmochimica Acta 63 (7-8): 1049-1057. Administration, London. Feibel, C.S., 1988. Paleoenvironments of the Koobi I.A.E.A./WMO, 2006. Global Network of Isotopes Fora Formation, Turkana Basin, Northern Ken- in Precipitation. The GNIP Database. ya. The University of Utah, p 329. Kaandorp, R.J.G., Vonhof, H.B., Del Busto, C., Wes- Feibel, C.S., 1999. Basin evolution, sedimentary selingh, F.P., Ganssen, G.M., Marmol, A.E., Pitt- dynamics and hominid habitats in East Af- man, L.R., van Hinte, J.E., 2003. Seasonal stable rica: an ecosystem approach. In: Bromage, T., isotope variations of the modern Amazonian Schrenk, F. (eds), African Biogeography, Cli- freshwater bivalve Anodontites trapesialis. Pal- mate Change and Human Evolution. Oxford aeogeography, Palaeoclimatology, Palaeoecol- University Press, Oxford, pp 276-281. ogy 194 (4): 339-354. Feibel, C.S., Brown, F.H., McDougall, I., 1989. Kaandorp, R.J.G., Wesselingh, F.P., Vonhof, H.B., Stratigraphic context of fossil hominids from 2006. Ecological implications from geochemi- the Omo group deposits - northern Turkana cal records of Miocene Western Amazonian Basin, Kenya and Ethiopia. American Journal bivalves. Journal of South American Earth Sci- of Physical Anthropology 78 (4): 595-622. ences 21 (1-2): 54-74. Feibel, C.S., Harris, J.M., Brown, F.H., 1991. Neo- Kingston, J.D., 2005. Orbital controls on seasonal- gene paleoenvironments of the Turkana Basin. ity. In: Brockman, D.K., Van Schaik, C.P. (eds), In: Harris, J.M. (ed), Koobi Fora Research Pro- Seasonality in Primates: Studies of Living and ject, Volume 3 Stratigraphy, Artiodactyls and Extinct Human and Non-human Primates. 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60 3. 87Sr/86Sr as a novel climate proxy recording precessional cycles in the hominin-bearing Turkana Basin

Josephine C.A. Joordens, Hubert B. Vonhof, Craig S. Feibel, Lucas J. Lourens, Guillaume Dupont-Nivet, Jeroen H.J.L. van der Lubbe, Mark J. Sier, Gareth R. Davies, Dick Kroon (In revision: Earth and Planetary Science Letters)

Abstract Introduction

Understanding the influence of orbital climate Climate and environmental changes must have cycles on hominin evolution remains a key chal- been important forcing factors in the evolution lenge in paleoanthropology. Two major issues of the human lineage, but the causal relation- are: the unavailability of a climate proxy yield- ships as well as the evolutionary mechanisms ing high-resolution (< 20 kyr) terrestrial climate involved are still not clarified (deMenocal, 2011). records, and the lack of age control on hominin Recently it has been argued that rapid and ex- fossil occurrences at sufficiently high resolution. treme climatic-environmental fluctuations on Here we present a novel climate proxy, strontium precession (~19-23 kyr) timescales, especially isotope ratios (87Sr/86Sr) of lacustrine fish fossils during eccentricity maxima, influenced hominin from the Turkana Basin, that solves these issues evolution and dispersal in Africa ( Potts, 2007; by recording orbitally forced variation in sum- Trauth et al., 2007; Maslin and Trauth, 2009). To mer monsoon intensity over the Ethiopian High- test these hypotheses, a high-resolution (< 20 lands. We successfully applied the climate proxy kyr) climatic and environmental framework for to a ~ 150 kyr time interval of ~2 million year old hominin fossil occurrences is required. Until now, paleolake deposits containing hominin fossils. the lack of high-resolution terrestrial climate Existing age control of the studied interval was proxy records precluded reconstruction of this improved by a new magnetostratigraphic record framework (Behrensmeyer, 2006). Even in the precisely locating the base of the Olduvai chron Turkana Basin (Kenya, Ethiopia) where a chrono- (C2n) near the bottom of the sequence. Spectral logical context has been well established (Feibel analysis demonstrates that 87Sr/86Sr variability is et al., 1989; McDougall and Brown, 2006, 2008; primarily determined by precession, which en- Feibel et al., 2009; Lepre and Kent, 2010) and or- ables us to place hominin fossils in an astronom- bital climate cycles were found to be reflected in ically-tuned climate framework. The Sr climate the lithostratigraphy (e.g. Lepre et al, 2007; Mc- proxy is potentially applicable to all hominin- Dougall et al, 2008), fossil occurrences could not bearing lake deposits in the Turkana Basin, be reliably correlated to precession cycles. ranging in age from ~ 4.2 to 0.8 million years ago (Ma). Our results show that between ~ 2 and 1.85 Due to its perennial riverine connection to the Ma the Turkana Basin remained well-watered Ethiopian Highlands, the Turkana Basin (Fig. 1a) and inhabited by hominins even during periods offers the rare opportunity to capture the or- of precession maxima when summer monsoon bitally-forced monsoonal climate signal in a con- intensity was lowest. This is in contrast to other tinental setting. Convective summer monsoon basins in the East African Rift System (EARS) rainfall in the Ethiopian Highlands is and was the that were impacted heavily by precession-forced primary water source of the Turkana Basin (Ar- droughts. We hypothesize that during lake phas- onson et al., 2008). Thus, orbitally-forced rainfall es, the Turkana Basin was an aridity refugium for variation in the Ethiopian Highlands is expected permanent-water dependent fauna –including to have dominated water chemistry changes of hominins- over the precessional climate cycles. recurrent (paleo)lakes in the basin. Strontium isotope ratios (87Sr/86Sr) provide a particularly 61 a b c 110 KBS Tuff 1.869 + 0.021 Ma

F 100

Ethiopia C3 M 90 E

Kenya SUDAN 80 36°15´E 36°30´E D

4°30´N 70 Lorenyang Tuff

M C2 C2 M C 41 60 C1

Il Dura C1 LEGEND 50 O Gastropods B4 15 4°15´N ETHIOPIA M Molluscs D Diatomaceous B 131 40 O Rhizoliths 3 Lake KENYA O Abundant fish remains O Gypsum B Turkana 115 30 O Convoluted boulders 100 4°00´N M Un/disconformity B Sand (>50%) 2 20 Silt 123 Clay A B1 10 3°45´N 20 km 0 D

Figure 1. a. Location of the Turkana Basin in Kenya and Ethiopia. Detailed map shows numbered paleontological sam- pling areas. b. Composite stratigraphy of the upper Burgi Member (UBU). C1, C2 and C3 are regional marker beds. c. Sampled subsections (see Fig. S2). useful record of such lake chemistry changes, of observed 87Sr/86Sr cyclicity to existing marine because lacustrine Sr isotope variation is solely climate records. Next, hominin fossil occurrences driven by water provenance. 87Sr/86Sr values of can be placed in the astronomically-tuned terres- well-preserved aquatic fossils (e.g. fish apatite) trial climate framework. from lake sediments directly reflect 87Sr/86Sr val- ues of host water in which they lived, and are not Background affected by temperature change or ecological pa- rameters (Talbot et al., 2000; Vonhof et al., 2003). Environmental and geologic setting – The Turkana Due to its conservative behavior, the hydrochem- Basin presently contains a saline-alkaline lake fed istry of dissolved Sr is a relatively buffered sys- primarily (~ 90%) by the Omo River that drains tem (Palmer and Edmond, 1989). It is therefore the Ethiopian Highlands. Minor contribution (~ expected that the 87Sr/86Sr climate proxy system 10%) is provided by the Turkwell-Kerio drainage filters out variation in riverine sources on sub- area in the SW of the basin (Yuretich, 1979) (Fig. millennial timescales, while remaining sensitive 1a). Climatic control is drastically partitioned, to changes on orbital timescales. with a headwater region climate in Ethiopia that is warm temperate or tropical, while the lower Hence, in this study we measure variation in sedimentary basin climate is hot arid or semi- strontium isotope ratios of fish apatite from ~ 2 arid (Feibel, 1999). From ~4.2 Ma onwards, the million year old lake deposits (upper Burgi Mem- Turkana Basin contained a major fluvial system ber, UBU; Fig. 1b) in the Turkana Basin, to resolve (paleo-Omo river), which alternated with sev- and quantify monsoon-driven rainfall cyclicity eral lake phases (Brown and Feibel, 1991). These on orbital timescales. In addition, we employ lake phases correspond to long-periodic (~ 400 magnetostratigraphic analysis to precisely iden- ky) humid episodes punctuating the long-term tify the base of the Olduvai chron in the studied Plio-Pleistocene drying trend in eastern Africa sequence. The resulting improved age control (Trauth et al., 2005; Trauth et al., 2007; Maslin allows spectral analysis of the Sr isotope record and Trauth, 2009). Within the humid episodes, to reveal orbital forcing, and subsequent tuning precession- and obliquity-driven changes be- 62 tween wet and dry monsoonal conditions caused in Area 102, suggesting occurrence of the rever- significant climatic and environmental fluctua- sal. Based on linear extrapolation of existing pa- tions, as evidenced in terrigenous dust records leomagnetic and radiometric data, the age of the obtained from marine cores (deMenocal, 1995; unconformity surface at the bottom of the upper Tiedemann et al., 1994). Such fluctuations have Burgi member is roughly estimated to be ~2 Ma also been observed in Plio-Pleistocene lake (McDougall and Brown, 2008). systems in the East African Rift System (EARS) (Ashley, 2007; Kingston et al., 2007; Owen et al., Methods 2008), including the Turkana Basin (Lepre et al., 2007; McDougall et al., 2008). However, so far the Sr isotope stratigraphy – To obtain a climate record observed cyclicity proved difficult to tie into the of early Lake Lorenyang, we analyzed 87Sr/86Sr astronomically-tuned climate framework derived of fossil fish apatite sampled at 1 m resolution from marine sediment cores. from the upper Burgi Member (UBU) in the Koobi Fora Formation. Sampling of UBU sediments took Climate-proxy relationship – One of the major lake place during fieldwork in 2006 and 2010 in Area phases in the Turkana Basin is Lake Lorenyang 102, near the Koobi Fora Field Station to the East that lasted between ~ 2.0-1.7 Ma, with the paleo- of present-day Lake Turkana (Fig. 1). To obtain a Omo from the North as its main water source and complete stratigraphic succession, undisturbed small rivers from the Southwest as minor water by faults, we stacked several sub-sections in Area sources (Feibel et al., 1991). Since the catchment 102 (Fig. 1c, Fig. S2, Table S1), using regional geology of the Omo and SW drainage areas is dis- marker beds C1, C2, C3, the Lorenyang Tuff and tinct (Fig. S1), the rivers have different chemical the KBS Tuff as stratigraphic tie points. Subsec- compositions, and variation of relative river con- tions were measured and trenched, after which tribution causes changes in lake water chemistry samples of unweathered sediment were taken at (Yuretich, 1979). Today as well as in the past, the 1 m intervals. Sediment samples were wet-sieved Omo River catchment drains flood basalts with and, when present, optically well-preserved fish relatively low 87Sr/86Sr values (~0.704) whereas fossils were picked under a binocular microscope. river catchments in the SW drain metamorphic Excellent preservation of fish fossils was con- rocks with relatively high 87Sr/86Sr values (> firmed by SEM inspection (Fig. 2). Only minor

0.720) (Talbot et al., 2000). Thus, during wet pe- diagenetic CaCO3 overgrowths were encountered riods in Ethiopia, the proportion of Omo water in cracks or voids in some of the fish fossils. To in the lake is expected to be relatively high, and effectively remove such possibly contaminant 87 86 Sr/ Sr values of lake water would tend towards CaCO3 phases, fish fossil fragments were leached that of Ethiopian Flood basalts (~ 0.704). During for ~1 hour in 5N acetic acid prior to Sr separa- dry periods in Ethiopia, the proportion of Omo tion. The remaining fossil apatite was dissolved 87 86 water in the lake was lower and Sr/ Sr values of in 3N HNO3, after which Sr was separated using lake water would increase. Elchrom Sr spec ion exchange resin. 87Sr/86Sr ra- tios were analysed on Finnigan MAT 261 and 262 Age control – The age of the studied interval (early mass spectrometers at the department of Earth Lake Lorenyang) is primarily constrained by the Sciences of the VU University Amsterdam, run- occurrence of the well-dated KBS Tuff (1.869 ning a triple jump routine and applying exponen- +/- 0.021 Ma; McDougall and Brown, 2006) at the tial fractionation correction. All 87Sr/86Sr data are top of the upper Burgi Member (UBU sequence, reported relative to a value of 0.710243 for the Fig. 1b). However, the age of the bottom is poorly routinely analysed NBS 987 standard. Sr in the constrained. Previous magnetostratigraphic re- blanks typically was < 0.01% of the total Sr in the sults from Area 102 indicated that the Lorenyang samples. Tuff is of normal polarity and located in the Olduvai chron, but the results from below the tuff Magnetostratigraphy – To better constrain the were difficult to interpret because of suspected basal UBU age, paleomagnetic sampling was secondary magnetization of these sediments performed during fieldwork in 2010 at ~50 cm in- (Hillhouse, 1986). Kamau (1994) later found re- tervals in the same UBU subsections of Area 102 versed polarities extending ~ 18 m upwards from where sediment samples for Sr isotope analysis the base of his (unspecified) upper Burgi section were collected. Paleomagnetic samples consisted 63

Figure 2. a: SEM photo of a partial fossil spine of Dasyatis africana (sample number K86-2382), a marine-derived stingray first appearing in the upper Burgi Member (Feibel, 1993). b: SEM photo of a fossil fish vertebra (sample number 06KF-B12).

of standard 2.5-cm-diameter cylindrical rock Initial Natural Remanent Magnetizations (NRM) cores drilled with an electric drill mounted with had intensities varying from 2.10-4 A.m to 6.10-2 a diamond-coated bit and cooled with an electric A.m. After removal of a common normal over- air compressor, both devices powered by a por- print up to 230 °C, the Characteristic Remanent table generator. Sampling of loose sandy inter- Magnetization (ChRM) was typically determined vals was done by pressing 2.5 cm diameter quartz by a steady decay towards the origin between glass cylinders, filled with a sodium silicate so- 230 and 400 °C with a sharp drop between 300 lution for in situ hardening, into the sediment. and 350 °C such that the interval between these Samples (cores and cups) were oriented with a temperatures was then reduced to steps of 20 °C compass and clinometer and no dip corrections in following demagnetizations (Fig. 3a). ChRM were necessary for these flat lying sediments. decay often extended above 400 °C in particular Orientations were corrected for the local 1.5 de- for the samples with the highest initial NRM in- gree declination. tensities. These demagnetization behaviors are Paleomagnetic processing was performed si- typical of Ti-rich titanomagnetites carrying the multaneously in paleomagnetic laboratories of remanence since there is no increase in suscep- the Utrecht University (The Netherlands), the tibility and NRM intensity observed above 350 Rennes University (France) and the CENIEH, Bur- °C, as would be expected for iron sulfides. ChRM gos (Spain). There were no significant differences directions were calculated using least square in the results from these three laboratories. Re- analysis (Kirschvink, 1980) on a minimum of four manent magnetizations were measured on 2G DC consecutive steps of the ChRM. Line fits were not squid magnetometers. A first selection of pilot anchored to the origin. ChRM directions with samples distributed every 4 m throughout the maximum angular deviation (MAD) above 30° sampled stratigraphy was stepwise thermally were systematically rejected. The resulting set of demagnetized in detail (steps: 20, 90, 150, 200, ChRM directions cluster around antipodal nor- 230, 260, 300, 330, 360, 400, 430, 460, 490, 520, 540, mal- and reverse-polarity mean directions (Fig. 560, 580, 600, 620 °C) in order to determine char- 3b) and pass the reversals test (McFadden and acteristic demagnetization behavior, establish McElhinny, 1990) with class C, suggesting stabil- the most efficient demagnetization temperature ity of the ChRMs, successful exclusion of normal steps, and localize stratigraphic intervals with overprint bias and a reliable magnetic polarity potential paleomagnetic reversals according to zonation. methods described in Dupont-Nivet et al. (2008). Alternating field demagnetization was performed Sr isotope and magnetostratigraphic results on 15 pilot samples but thermal demagnetization of sister samples gave superior component sepa- The resulting 87Sr/86Sr record shows a trend from ration and was used in all following processing. relatively low values (0.7048) in the base of the 64 a. Typical demagnetizations

up/W 20

100

150 KA170 up/W 600 550 200 N KA036 520 360 490 300 460400 330 200 230 250 290 260 150 320 330 350 N

b. ChRM directions

Normal D = 4.3; I = 0.2 n = 44; k = 17.1

Reversed D = 180.3; I =-4.0 n = 17; k = 7.9

Figure 3. a. Vector end point of typical thermal demagnetizations of normal (left) and reversed (right) polarity direc- tions respectively. Full (open) symbols are projections on horizontal (vertical) plane. Best fit directions are indicated by line through temperature steps of the ChRM component above 230 ºC. b. Left: Characteristic Remanent Magnetization (ChRM) directions projected in lower (full symbol) and upper (open symbol) hemispheres of stereogram. Right: mean of the normal and reversed directions respectively. D = declination; I = inclination; n = number of ChRM directions; k = precision parameter of Fischer statistics. section towards relatively high values in the top in line with the expected high contribution of part of the section (> 0.7052), with distinct cyclic Omo River water to the basin. changes in Sr isotope ratios superimposed on the Two distinct paleomagnetic polarity intervals long-term trend (Fig. 4, Table S2). 87Sr/86Sr values separated by a reversal are clearly identified by are close to the Omo catchment value of ~ 0.704, the distribution of normal and reverse directions 65 1.869 + 0.021 Ma KBS Tuff

1mm Olduvai chron (C2n)

1.945 + 0.004 Ma

Figure 4. Magnetostratigraphy and Sr isotope record in Area 102, showing the exact position of the base of the 0.7056 0.7054 0.7052 0.705 0.7048 0.7046 Olduvai chron in the Sr isotope cycle. Inset photo is an 87Sr/86Sr fish apatite example of typical fossil fish apatite (in this case, a fish vertebra) used for Sr isotope analysis.

(Fig. 4, Table S3). The consistency of the polarity provided by linear fit between stratigraphic posi- directions within those polarity intervals further tions of the top of the Olduvai chron (Lepre and supports the reliability of our data. In addition, Kent, 2010) with an astronomically-tuned age of the reversal is recorded in two parallel subsec- 1.778 +/- 0.003 Ma and the newly established base tions where careful demagnetization of all col- of the Olduvai chron with an astronomically- lected samples was performed to obtain the best tuned age of 1.945 +/- 0.004 Ma (Lourens et al, possible resolution for the stratigraphic position 2004). The top of the Olduvai chron is located in of the reversal (Table S3). Correlation of this re- the KBS Member overlying the UBU in Area 102, versal to the base of the Olduvai chron (bC2n) is placed at 49 m above the KBS Tuff (Lepre and unequivocal. The KBS tuff at the top of the sec- Kent, 2010). Spectral analysis of the Sr isotope tion is clearly located within the top part of the record (see supplementary text S1) reveals one Olduvai chron. Observed polarities below the KBS significant (~90 %) peak in the orbital frequency tuff are continuously and consistently normal band around 21 ky, pointing to a dominant pre- until the observed reversal, below which the ob- cession (19-23 ky) controlled climatic origin of served polarities are exclusively reversed. Our re- the 87Sr/86Sr variability (Fig. 5). Band-pass Gauss- sults confirm the presence of and precisely locate ian filtering of the ~21 ky period shows that the the base of the Olduvai chron in our Sr isotope 87Sr/86Sr record contains ~6 precession-related record near the bottom of the section, between climate cycles (Fig. 5). a 87Sr/86Sr maximum (dry period) just below and a 87Sr/86Sr minimum (wet period) just above the Climate modeling studies have shown that during paleomagnetic transition (Fig. 4). precession minima monsoon precipitation in the Omo River catchment would be relatively high Spectral analysis and tuning of the Sr isotope (Tuenter et al., 2003; Aronson et al., 2008) causing record 87Sr/86Sr values of Turkana Basin lake water to de- crease. Hence, by tuning the precession-related A first-order chronology for the87 Sr/86Sr record is variations in the 87Sr/86Sr record to the climatic 66 a 3.0 0.8

2.0 0.4 ) ) -4 -4 1.0

Sr (10 Sr 0 (10 Sr 86 86 (detrended) (21-kyr filter) Sr/ 0.0 Sr/ 87 87

-0.4 -1.0

-2.0 -0.8 1820 1840 1860 1880 1900 1920 1940 1960 Linear interpolated age (ka)

1E-006 b 21.1 kyr

1E-007 95% (χ2) Gxx_corr 90% (χ2) 80% (χ2)

1E-008 0 0.05 0.1 0.15 0.2 0.25 Frequency (1/kyr)

Figure 5. a. Band pass Gaussian filtering of the detrended Sr isotope record according to the linear paleomagnetic constraint age model. b. Bias-corrected spectrum (Gxx_corr) of the 87Sr/86Sr record according to the linear paleomagnetic constraint age model. precession index we were able to increase the constant sedimentation rate. In the first option chronological resolution of the studied sedi- (Age model 1), the oldest 87Sr/86Sr maximum was ments. For tuning we applied the 65°N summer tuned to a minimum insolation value, numbered insolation of the La2004(1,1) astronomical solution i-189 (Lourens et al., 1996), at 1.958 Ma (Fig. S3). (Laskar et al., 2004), because this target curve Subsequently, all successive minima (maxima) in clearly reflects the distinct precession-obliquity the filtered87 Sr/86Sr record were correlated to the interference patterns recorded by the monsoon successive maximum (minimum) insolation val- intensity related sapropel depositions in the ues. This age model results in a tuned age for the Mediterranean (Lourens et al., 1996; 2004). bC2n of ~ 1.949 Ma being close to the ATNTS2004 age of 1.945 +/- 0.004 Ma (Lourens et al., 2004). Taking the position of the base of the Olduvai However, the tuned age of the KBS (1.841 Ma) is chron as time anchor, four tuning options will be more than one precession cycle younger than its discussed (Fig. 6). The first age model assumes a radiometric age of 1.869 +/- 0.021 Ma (McDou- 67 1750 Olduvai (top) Radiometric ages Olduvai Age 1 1800 Age 2 Age 3 Age 4

1850 Malbe tuff

ge (ka ) KBS tuff A

1900

Olduvai (base) 1950

2000 160 120 80 40 0 -40 Position (m)

Figure 6. Age versus depth plot of top and base of the Olduvai chron, and of the KBS and Malbe Tuffs. Coloured lines indicate sedimentation rates for the four tuning options Age 1, Age 2, Age 3, Age 4.

gall and Brown, 2006). In our second option (Age the 87Sr/86Sr record. In addition, we considered model 2), we shifted the tuning of the 87Sr/86Sr that the oldest part of the record represents two record by one cycle older (Fig. S4). This results instead of one precession-related cycle due to the in a tuned age for the KBS of 1.863 Ma, close to low sedimentation rates associated with the clay- its radiometric derived age, but in this case the rich depositions in this interval. In the third op- resulting age of the bC2n becomes ~25 kyr older tion (Age model 3) we tuned the oldest 87Sr/86Sr than the astronomically-tuned age (Lourens et maximum of these two cycles to the minimum al., 2004). insolation value, numbered i-191 (Fig. 7), and in the fourth option (Age model 4, Fig. S5) to i-193 In the next two age models, we inferred the pos- (Lourens et al., 1996). Age model 3 results in an sibility of variable sedimentation rates between age for the bC2n of ~ 1.955 Ma, ~10 kyr older than the of clay and sandy deposits (Fig. 6). In par- the astronomically-tuned age, while the bC2n be- ticular, assuming that the thick sandy interval comes ~10 kyr younger according to Age model 4. between ~25 and 45 m represents an interval of Following Age model 3, the tuned age of the KBS high sedimentation rates, this might have intro- Tuff (i.e., 1.863 Ma) is more consistent with its ra- duced an artificial precession-related cycle in diometric age of 1.869 +/- 0.021 than that in Age 68 model 4 (i.e., 1.841 Ma). For this reason we cur- For the Omo River catchment we chose a typical- rently prefer Age model 3. An argument that may ly basaltic 87Sr/86Sr value of 0.7046 and a typical plead for Age model 4, however, could be that Sr concentration of 0.079 ppm (Table S4). These the pattern of the 87Sr/86Sr record fits better with end members values were subsequently used to the estimated dust records of Site 659 off North- calculate what percentual changes of Omo versus west Africa (Tiedemann et al., 1994) and of Site SW river catchment contribution are required to 721/722 off Oman (deMenocal, 1995; not shown), cause the observed 87Sr/86Sr cyclicity on preces- and with the precession-obliquity interference sion time scales (Fig. S6). In this context, the long patterns in the Mediterranean sapropel succes- linear trend towards higher 87Sr/86Sr values in sion (compare Figs. 7 and S5). In view of the on- the UBU record (Fig. 4) can either be considered going debate on the accuracy of radiometrically to represent slowly changing water chemistry dated tuff ages (Kuiper et al., 2008; Channell et in any of the two catchments, or to reflect a al., 2010, Renne et al., 2010), we cannot exclude gradual relative decrease of rainfall in the Omo the possibility that the KBS Tuff may ultimately catchment. Since the purpose here is to quantify turn out to be younger or older than currently changes on precession time scales, we removed accepted. Given these uncertainties, we chose to the long trend prior to our calculations. It is fur- discuss here the implications of Age model 3 for ther relevant to note that geologically reasonable the hominin fossil occurrences in relation to re- variation in end member values (Sr isotope ratio gional climate conditions and glacial-interglacial and Sr concentration) has little to no effect on variability, while the full comparison of the alter- the percentual changes in catchment contribu- native age models are presented in the supple- tion as calculated by the binary mixing model. mentary figures S3-S5. These calculations demonstrate that no more than 5-10% variation in Omo catchment input is Modeling precession-related variation in required to explain the precession-related varia- Omo River input tions in the 87Sr/86Sr cycles (Fig. 7, Fig. S3-S5).

In order to assess the impact of precessional Placing hominin fossils in the climate frame- modulation on hominin environments in the work Turkana Basin, we quantified the monsoon- driven rainfall cyclicity reflected in the Sr iso- Since the upper Burgi deposits in Area 102 com- tope record. Since 87Sr/86Sr is essentially a water prise mostly pelagic and prodeltaic sediments provenance indicator, relative changes in water (Feibel, 1988), fossils from terrestrial fauna such contribution of Omo and SW catchments to the as hominins are rare. Most hominin fossils (rep- Turkana Basin can be calculated by applying a bi- resenting possibly three different species) from nary mixing model (Vonhof et al., 2003; Joordens the UBU derive from deltaic sediments in the et al., 2009). Required model input parameters Bura Hasuma and Karari Ridge regions (Feibel et are the Sr isotope ratio and the Sr concentra- al., 1989; Fig. 1). To place hominin fossil occur- tion of both catchments. Modern river water rences from these regions in the astronomically- chemistry of these catchments is not necessarily tuned framework obtained from the Sr record in representative for the Lower Pleistocene (~ 2 Ma) Area 102, UBU deposits in Area 102 and other re- situation due to anthropogenic influence on Omo gions have to be correlated. Thickness and pres- and SW river chemistry, and significant Middle ervation of UBU deposits differ between regions and Upper Pleistocene changes in the geology of in the Turkana Basin (Brown and Feibel, 1991). To the SW catchment. Therefore we approximated correlate UBU deposits in different regions, we Lower Pleistocene riverine end member values employed lithostratigraphic scaling in combina- by adapting values given for comparable catch- tion with Sr isotope stratigraphy (see supplemen- ments elsewhere (Palmer and Edmond, 1989; tary text S2). Talbot et al., 2000; Vonhof et al., 2003). For the SW rivers end member we chose a typically cra- Beased on the obtained correlations, we cal- tonic 87Sr/86Sr value of 0.724 (Table S4). The cor- culated tuned ages for 12 hominin fossils from responding Sr concentration of 0.0107 ppm is the UBU deposits in Areas 123, 102 and 100 (Feibel average value that was applied for similar craton- et al., 1989; Table S6). These 12 hominin fossils ic catchments in Amazonia (Vonhof et al., 2003). are placed in the cyclostratigraphic framework. 69 Age model 3

Mediterranean sapropel (s) 560 a 65N summer insolation s s s s s 520 s s 2 m / 480 W 440 b 17 9 18 1 18 3 18 5 18 7 18 9 17 7 17 3 17 5 19 1 19 3 ------i i i i i i i i i i 20.0 i ) %

( 30.0 t s

u 40.0 D 50.0 ODP 659

c Turkana -2 95% Omo contr. ) 4 -

0 -1 ed ) 1 ( d

n 90% Omo contr.

Sr 0 6 tr e 8 Sr / (d e 7 1 8 85% Omo contr. 2

d Hominin fossils FwJj20 KBS Lorenyang e Tuff layers KBS base Olduvai 3.2 f

) 3.4 ‰ ( 3.6 O 8 1 δ 3.8 68

4 62 66 70 72 64 74 Pleistocene Pliocene Olduvai

1750 1800 1850 1900 1950 2000 Age (ka)

70 The resulting pattern has distinct stratigraphic through the precessional wet-dry climate cycles gaps in fossil occurrence (Figs. 7, Fig. S3-S5). of the studied time interval. Such a small change Significantly, these gaps bear no clear relation is unlikely to have had a significant effect on to precesional cyclicity, but relate to facies pat- Turkana Basin water balance. Our calculations terns in the early Lake Lorenyang sequence, with suggest that sustained input of Omo River water hominin fossils derived primarily from deltaic to the Turkana Basin maintained river, delta and deposits. Our results indicate that hominin fos- lake margin habitats throughout the precession- sils are present in sediments deposited during driven climate cycles (and obliquity-driven wet as well as during dry periods. The hominin glacial-interglacial variability) in early Lake Lo- site FwJj20 (Area 41; Fig. 1), stratigraphically lo- renyang times. In contrast, records from other cated just below the base of the Olduvai chron EARS lake basins show severe drought and chang- (Braun et al, 2010), can also reliably be placed in es in lake level and chemistry to occur at preces- the cyclostratigraphic framework indicating that sion frequencies (Kingston et al., 2007; Trauth et it (in both Age models 3 and 4) occurred in a dry al., 2007; Owen et al., 2008; Maslin and Trauth, period. 2009; Trauth et al., 2010).

Discussion and conclusions This spatial heterogeneity in environmental response to climate forcing can largely be ex- Our data demonstrate that the new 87Sr/86Sr plained by the exceptional hydrology of the climate proxy, providing its application is well Turkana Basin, with a perennial watersource constrained in time, allows unprecedented in the vast Ethiopean Highlands (Feibel, 1999). high-resolution astronomical tuning of the rich Where neighboring lake basins were impacted Turkana Basin fossil record with an uncertainty dramatically by precessional climate cyclicity, of one precession cycle. For the first time it has the lacustrine Turkana Basin remained relatively been unequivocally demonstrated with a terres- impervious to precession-forced extreme climate trial climate proxy that precession cycles are the fluctuations or glacial cyclicity. We hypothesize main driver of orbital fluctuations in Omo river that as such, it could function as an aridity refu- water input into the Turkana Basin, and hence gium for permanent-water dependent lake shore of orbital fluctuations in monsoon intensity over and delta-dwelling terrestrial fauna (likely in- the Ethiopian Highlands. The climate proxy is cluding hominins) during regionally dry periods. potentially applicable to all fossil-bearing lake Our results show that hominins appear to have phase deposits in the Turkana Basin, ranging in been present during both wet and dry periods of age from ~ 4.2 to 0.8 Ma and covering a total time the precession cycles. Particularly, the magneto- of ~ 950 ky (Brown and Feibel, 1991). It offers im- stratigraphically well constrained hominin local- proved age control coupled with high-resolution ity FwJj20 (Braun et al., 2010) suggests that re- regional climate information. This combination markably well-watered, vegetated environments of data is pivotal for further testing and refining were present during a dry period of precession of climate-evolution hypotheses (e.g. Maslin and maximum configuration. The Turkana Basin thus Trauth, 2009). appears to occupy a unique position among EARS basins over the past 4 My, due to its geographi- Based on the binary mixing model, we recon- cal setting “at the mouth of the funnel” draining structed fluctuations in Omo River water input the Ethiopian Highlands. These exceptional hy- to the Turkana Basin of no more than 5-10%, drological conditions, sustaining lake shore and

Figure 7 (left). Tuning option Age 3. a. Summer insolation at 65º N according to the La2004(1,1) solution (Laskar et al., 2004; Lourens et al., 2004), with positions of the Mediterranean sapropels indicated (Lourens et al., 1996). b. Dust record of Site 659 off Northwest Africa (Tiedemann et al., 1994). c. Detrended and tuned Sr isotope record from Area 102 in the Turkana Basin. Dashed lines show the proportion of Omo River water in the lake calculated with a binary mixing model. d. Hominin fossil occurrences plotted relative to wet and dry periods (vertical yellow bars) of the precession-driven cli- mate cycles. Also indicated (full circle) is the hominin site FwJj20 in Area 41 of the E Turkana Basin (Braun et al., 2010). e. Stratigraphic positions of KBS and Lorenyang Tuff layers and bC2n in the tuned Sr isotope record. Open diamond symbol = radiometric age of the KBS Tuff. f. ∂18O stack based on ODP Leg 154 sites with numbered Marine Isotope Stages (Bickert et al., 1997; Wang et al., 2010). 71 delta habitats throughout precession cycles, may al Atlantic deep-water circulation: inferences in part explain the richness of the Turkana Basin from benthic stable isotopes. In: Shackleton, hominin fossil record during the Lorenyang lake N.J., Curry, W.B., Richter, C., Bralower, T.J. phase. (Eds.), Proc. ODP, Sci. Results 154: 239-253. Brown, F.H., Feibel, C.S., 1991. Stratigraphy, depo- Acknowledgements sitional environments and paleogeography of the Koobi Fora Formation. In: Harris, J.M. (Ed.), This study was supported by: the Netherlands Koobi Fora Research Project, Volume 3 Stratig- Organisation for Scientific Research (NWO), the raphy, Artiodactyls and Paleoenvironments, Center for Human Evolutionary Studies (CHES, Clarendon Press, Oxford, pp. 1-30. Rutgers University), the National Science Foun- Channell, J.E.T., Hodell, D.A., Singer, B.S., Xuan, dation (NSF USA) and the Leakey Foundation. We C., 2010. Reconciling astrochronological and gratefully acknowledge the National Museums 40Ar/39Ar ages for the Matuyama-Brunhes of Kenya and the Government of Kenya for fa- boundary and late Matuayama Chron. G3, doi: cilitating our research in the Koobi Fora region. 10.1029/2010GC003203. We thank Rhonda Quinn, Chris Lepre and Hen- deMenocal, P.B., 1995. Plio-Pleistocene African ning Scholz for cooperation in the field. We owe climate. Science 270: 53-59. thanks to Kamoya Kimeu, Paul Mulinge, Ndolo deMenocal, P.B., 2011. Climate and human evolu- Muthoka, Muthoka Kivingo, Halewijn Scheuer- tion. Science 331: 540-541. man†, the Koobi Fora Research Project (Louise Dupont-Nivet, G., Sier., M., Campisano, C.J., Ar- Leakey, Meave Leakey) and the Turkana Basin rowsmith, J.R., DiMaggio, E., Reed, K., Lock- Institute for logistical support in the field. Saskia wood, C., Franke, C., Hüsing, S., 2008. Mag- Kars conducted Scanning Electron Microscopy netostratigraphy of the eastern Hadar Basin on the fish apatite. Marin Waaijer, Martijn Klaver, (Ledi-Geraru research area, Ethiopia) and Trine Kellberg Nielsen, Monika Knul and Krijn implications for hominin paleoenvironments. Boom provided analytical assistance. Comments In J. Quade & J.G. Wynn (Eds.), The geology of by Fred Spoor, Adam Jagich, Martin Trauth, Peter early humans in the Horn of Africa: Geol. Soc. deMenocal and anonymous reviewers greatly im- Am. Special Paper 446: 67-85. proved an earlier version of this manuscript. This Feibel, C.S., 1993. 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Supplementary information

S1. Spectral analysis and tuning – We applied the time series was filtered using a Gaussian filter computational spectral analysis program, REDFIT as implemented in the freeware AnalySeries 2.2 version 3.8 (Schulz and Mudelsee, 2002) on the (Paillard et al., 1996). The filtered frequency was detrended 87Sr/86Sr record. In this model a first- centered at 0.047 ± 0.005. order autoregressive progress (AR1), which is assumed to present a good estimate of the red- S2. Placing hominins in the cyclostratigraphic noise signature, is estimated directly from the framework – Due to conservative behaviour of Sr (unevenly spaced) time series and, subsequently, in lake water (Faure, 1986) temporal Sr-isotope transferred into the frequency domain using evolution of well-mixed lake water will be the Lomb-Scargle algorithm. Confidence levels identical at all regions under study in the eastern based on a χ² distribution are calculated from Turkana Basin. Temporal Sr-isotope changes the AR1-noise and from percentiles of the Monte during Lake Lorenyang times were influenced by Carlo ensemble (not shown). For the analysis, we climatic fluctuations on precession timescales, applied one WOSA segment (n50=1), 2000 Monte but also by processes occurring on longer Carlo simulations (Nsim=2000), an oversampling timescales: i.e. any long-term climatic trend factor (OFAC=4) and a rectangular window and/or reorganization in the Omo and/or SW (Iwin=0). The analysis was performed on the catchment areas, such as autocyclic progradation linear age model constrained by the top and base of the Omo delta down the eastern lake margin of the Olduvai, resulting in an average sampling over time (Feibel, 1988). Lake deposits from Area resolution for the 87Sr/86Sr record of 1.9 kyr. 102 recorded a temporal trend in 87Sr/86Sr values The ~21 ky component of the untuned 87Sr/86Sr (Fig. 4) analogous to the long-term temporal 74 Section Subsection Latitude Longitude Marker bed

Abegin 3.57382 36.14379

Amid 3.57310 36.14450 Gypsum bed

Aend 3.57303 36.14455

B1 begin 3.57401 36.14585 B 3.57390 36.14600 Gypsum bed 1 end B 3.57334 36.14597 Gypsum bed 2 begin B2 mid 3.57326 36.14591 Cemented bed with molluscs

B2 mid 3.57318 36.14597 Cemented bed with molluscs

B2 end 3.57310 36.14588 B 3.57301 36.14606 3 B 3.57295 36.14602 3 B4 3.57289 36.14621

B4 3.57283 36.14624 C1

C1 begin 3.57215 36.14318 C1

C1 end 3.57220 36.14323 C2

C2 begin 3.57154 36.14312 C2

C2 end 3.57149 36.14315 Lorenyang Tuff

D1 begin 3.56888 36.13914 Lorenyang Tuff

D1 end 3.56837 36.13766 Sandstone bed

E1 begin 3.56857 36.13919 Sandstone bed

E1 end 3.56834 36.13764 C3

F1 begin 3.56902 36.13680 C4

F1 end 3.56900 36.13674 3.56915 36.13658 KBS Tuff

Table S1. GPS control points for sections and subsections of UBU in Area 102 (see Fig. A2). GPS coordinates are given using the WGS1984 datum.

trend in Sr isotope ratios of seawater that can and C1 in Area 102. Next, Sr isotope ratios of be used for chronology (Faure, 1986). This Sr fish fossils from Areas 123, 104 and 102* were reference curve can be employed as a first-order plotted on the Sr isotope record of Area 102 stratigraphic tool to corroborate or establish (Fig. S7), showing that the values coincide with correlations between UBU in Area 102 and UBU those of the Sr isotope reference curve from sections cropping out in other regions east of the Area 102, thus corroborating the correlations. lake. Because the hominin-rich UBU deposits at the Karari Ridge do not share marker beds To this end, we analyzed Sr isotope ratios of with Area 102, stratigraphic scaling cannot be aquatic fossil samples collected in different used for correlation. The consistently low Sr regions (Bura Hasuma, Koobi Fora Ridge, Karari isotope ratios of the Karari fish fossils (Table Ridge) in the eastern Turkana Basin (Fig. 1, S5) suggest that the deposits below marker bed Table S5). To correlate UBU deposits from Area LCC at the Karari Ridge match with the Area 102 123 and Area 102, we used stratigraphic scaling UBU deposits just above and further below the with marker bed C4 (Feibel et al., 2009) as a tie base of the Olduvai chron. However, Sr isotope point to calculate a scaling factor to convert stratigraphy and magnetostratigraphy needs “local m levels” in Area 123 into “m levels in to be done at the Karari Ridge before hominin Area 102”. Aquatic fossils obtained from securely fossils from this region can be reliably placed in identified levels (C2 complex, C1) in Areas the cyclostratigraphic framework. 123, 104 and 102* (see caption Table S5) were assigned to the typical m level for C2 complex 75 Comp. m Comp. m Sample level 87Sr/86Sr 2-sigma Sample level 87Sr/86Sr 2-sigma K85-2242 106 0.705292 0.000009 06KF-B34II 43.5 0.704955 0.000012 K7 103 0.705602 0.000009 06KF-B32II 41.5 0.704953 0.000015 06KF-BaseC3 93 0.705344 0.000013 06KF-B29II 38.5 0.704936 0.000009 C3-10 cm-1 92.9 0.70534 0.000009 06KF-B28II 37.5 0.70491 0.000011 C3-10cm-2 92.8 0.70529 0.000006 06KF-B25II 34.5 0.704904 0.00001 06KF-B24 90 0.705309 0.000007 06KF-B22II 31.5 0.704876 0.00001 06KF-B22 88 0.705272 0.00007 06KF-B21II 30.5 0.704934 0.000009 06KF-B18 84 0.705372 0.000014 06KF-B20II 29.5 0.704894 0.000009 06KF-B16 82 0.705267 0.000008 18-22 m a.u. 28.5 0.704831 0.000011 06KF-B14 80 0.705368 0.000012 06KF-B18II 27.5 0.704923 0.000011 06KF-B12 78 0.70548 0.00002 06KF-B17II 26.5 0.705022 0.000014 06KF-B10 76 0.705425 0.000013 06KF-B15II 24.5 0.705074 0.000009 06KF-B8 74 0.705446 0.00002 06KF-B14II 23.5 0.705145 0.000014 06KF-B4 70 0.705354 0.000016 06KF-B13II 22.5 0.705145 0.000017 06KF-B60II 69.5 0.705251 0.00001 06KF-B8II 17.5 0.704839 0.000012 06KF-B59II 68.5 0.705281 0.000004 10KF-B16 16 0.704844 0.000007 06KF-B2 68 0.705146 0.000016 06KF-B6II 15.5 0.704821 0.00001 06KF-B58II 67.5 0.705014 0.000026 10KF-B15 15 0.704817 0.000008 06KF-B58II 67.5 0.704999 0.000006 06KF-B4II 13.5 0.704742 0.00001 06KF-B0 67 0.704934 0.000016 06KF-G3II 12.5 0.704738 0.00001 06KF-B56II 65.5 0.705158 0.000008 10KF-B12 11.5 0.704872 0.000011 06KF-B54II 63.5 0.705181 0.000011 06KF-B2II 11.5 0.704996 0.000024 06KF-B52II 61.5 0.705214 0.000008 10KF-B11 10.5 0.705072 0.000009 06KF-B51II 60.5 0.705188 0.00001 10KF-B10 10 0.705047 0.000012 06KF-B50II 59.5 0.70529 0.000009 06KF-B0II# 9.5 0.705066 0.000012 06KF-B49II 58.5 0.705267 0.000018 10KF-B8 8 0.704803 0.000009 06KFB46II 55.5 0.705131 0.000009 10KF-B7 7 0.704842 0.000011 06KF-B46II* 55.5 0.705094 0.000011 10KF-B6 6 0.70501 0.000008 06KF-B44II 53.5 0.705088 0.000007 KJ10-2 5 0.705015 0.00001 06KF-B42II 51.5 0.705055 0.00001 10KF-B4 4 0.704984 0.000017 06KF-B40II 49.5 0.705054 0.000009 10KF-B3 3 0.70506 0.000009 06KF-B38II 47.5 0.705049 0.000011 10KF-B2 2 0.704891 0.000009 06KF-B36II 45.5 0.704947 0.000021 10KF-B1 1 No data Diatomite 10KF-B0 0 No date Diatomite

Table S2. Sr isotope ratios of aquatic fossils sampled from Area 102. Comp. m level: meter level in the composite sec- tion.

76 Sample level Dec Inc NRM MAD Pol Sample level Dec Inc NRM MAD Pol (m) (°) (°) mA.m (°) (m) (°) (°) mA.m (°) Main New section section (B) (A) KA157 93.5 352.4 -11.3 55.9 6.1 N KA060 22.0 358.1 -11.4 5.1 4.9 N KA158 92.5 348.5 18.4 37.4 15.1 N KA059 21.5 14.9 -9.2 2.7 13.4 N KA159 91.9 347.5 -20.1 19.1 4.3 N KA056 20.0 15.8 3.3 1.1 25.6 N KA161 89.6 1.0 3.3 8.4 4.3 N KA052 18.0 20.0 -11.1 0.7 11.7 N KA162 88.6 17.7 -16.0 10.3 19.5 N KA050 16.5 35.6 -5.1 0.5 12.2 N KA163 88.2 17.1 -8.2 34.3 6.2 N KA049 15.5 341.2 -7.6 3.2 8.8 N KA171 81.2 6.6 6.3 15.1 5.4 N KA048 14.5 340.2 -18.0 1.0 9.2 N KA175 78.0 9.3 22.4 35.9 11.1 N KA047 13.5 335.1 4.9 1.4 5.3 N KA146 70.5 0.2 16.9 5.6 6.8 N KA046 13.0 30.0 5.7 2.0 14.4 N KA153 66.5 2.0 14.8 22.2 8.7 N KA045 12.5 143.2 -49.4 2.7 13.5 R KA133 61.3 12.6 1.1 7.4 4.4 N KA044 12.0 191.2 24.0 0.4 21.0 R KA134 60.5 9.9 -9.0 5.2 3.8 N KA043 11.5 224.5 4.8 3.3 15.5 R KA109 60.3 356.3 2.4 8.1 2.6 N KA042 11.0 190.0 -6.2 2.8 18.4 R KA093 53.9 11.1 -5.3 8.6 12.3 N KA041 10.5 185.1 -17.8 1.9 27.8 R KA095 52.8 45.3 0.2 21.0 3.3 N KA040 10.0 153.3 -16.7 0.3 11.4 R KA102 49.0 17.2 19.4 56.8 8.7 N KA039 9.5 183.9 17.6 0.8 1.4 R KA105 46.5 13.9 5.8 2.9 6.6 N KA036 8.0 172.5 -18.9 0.7 7.2 R KA106 46.0 359.8 -4.1 2.7 6.3 N KA032 6.0 191.9 -4.2 0.9 9.0 R KA079 45.9 353.1 -1.0 6.6 3.0 N KA028 4.0 216.8 -13.5 0.4 14.8 R KA090 39.5 1.0 -11.0 3.6 10.8 N KA027 3.5 170.3 20.0 1.3 7.7 R KA123 31.6 358.3 11.6 11.7 4.1 N KA025B 2.5 154.9 11.7 0.2 10.6 R KA121 29.2 344.9 -5.5 9.9 4.5 N KA024A 2.0 180.6 14.1 0.4 9.4 R KA077A 28.4 333.4 -4.4 20.3 2.2 N KA022B 1.0 177.3 2.5 13.1 8.9 R KA074 26.7 349.0 3.1 5.4 12.7 N KA021A 0.5 180.2 2.6 1.1 3.7 R KA071 24.3 8.4 15.8 18.9 18.5 N KA020A 0.0 185.3 1.0 0.2 18.8 R KA064 20.0 5.7 9.5 1.8 9.0 N KA019A 17.5 351.0 7.5 4.3 15.9 N KA016A 15.5 4.1 4.2 1.3 14.3 N KA014A 14.0 0.6 0.7 2.9 18.4 N KA013A 13.3 1.2 -6.3 3.5 13.9 N KA008B 8.1 6.4 -10.3 2.4 13.9 N KA007B 7.3 24.7 -2.5 0.4 9.7 N KA005B 5.0 32.7 -13.9 2.1 25.9 N KA004B 3.8 342.8 13.5 1.5 8.7 N KA003B 2.9 6.6 -6.2 0.6 2.7 N KA002A 1.9 41.4 20.1 1.7 5.8 N KA001A 1.5 143.1 -39.8 1.3 7.9 R

Table S3. Magnetostratigraphic results. Sample: sample identification; Level: stratigraphic level above base of section B (left column) and A (right column); Dec: Declination of ChRM direction; Inc: Declination of ChRM direction; Int: Intensity of ChRM; MAD: Maximum Angular Deviation; Pol: Observed polarity. N: Normal; R: Reversed.

[Sr] Omo River 0.079 ppm [Sr] SW Rivers 0.0107 ppm 87Sr/86Sr Omo River 0.7046 87Sr/86Sr SW Rivers 0.7240

Table S4. Input values binary mixing model. [Sr] = Strontium concentration in ppm (parts per million).

77 Area Strat. level Sample code Sample type local m m in 102 87Sr/86Sr 2-sigma 123 C4-5m K85-2281 stingray sting 55 98.5 0.705293 0.000006 123 C4-7m K86-2391 stingray sting 53 94.9 0.705390 0.000010 123 C2 compl. KJ06-30 shell 58.0 0.705117 0.000006 123 OS K86-2356 fish tooth 32 57.3 0.704955 0.000008

104 C2 compl. K05-7555 shell fragment 58.0 0.705089 0.000011 102* C2 compl. K85-2241 fish tooth 58.0 0.704987 0.000007 102* C1 K86-2341 fish tooth 46.0 0.705069 0.000008

105 LCC K86-2380 stingray sting 0.704946 0.000008 105 LCC-1m K86-2381 stingray sting 0.704826 0.000008 105 GPC K86-2397 fish tooth 0.704932 0.000008 105 F+ K86-2382* stingray sting 0.704924 0.000008 105 F K86-2382 stingray sting 0.704967 0.000009

117 GPC K86-2379 stingray sting 0.704852 0.000012 117 GPC- K86-2489 stingray sting 0.704845 0.000009 118 F K86-2395 stingray sting 0.704744 0.000008 115 F K86-4015 stingray sting 0.704902 0.000009 131 KBS-36 K85-2278 stingray sting 0.704759 0.000009

Table S5. Sr isotope ratios of fish fossils from Areas 123, 104, 102, 105, 115, 117, 118 and 131 (Fig. 1). These samples (except KJ06-30) were collected by CSF in 1985, 1986 and 2005. The samples from “Area 102*” were collected in Area 102 in 1985-1986, not from the stacked sequence sampled in Area 102 in 2006. Sample KJ06-30 was collected by JJ and CSF in 2006. Stratigraphic provenance of fish fossils is logged in relation to m level above/below marker beds in the find areas: C1, C2 compl. (C2 Complex), C4, OS (Ostracod Sands), LCC (Limonite Chunk Conglomerate), GPC (Gold Pebble Conglomerate), f, and KBS (KBS Tuff) (Feibel,1988; Feibel et al., 1989; Feibel et al., 2009).

local m m level in Fossil KNM-ER Taxon Area Strat. level level 102 Tuned age (Ma) 1501 Homo sp. 123 C4-40 m 20 35.8 1.9212 1502 Homo sp. 123 C4-12 m 48 85.9 1.8693 5879 Homo sp. 123 C4-12m 48 85.9 1.8693 1813 Homo sp. 123 C4-11m 49 87.7 1.8683 1810 postcranial 123 C4-7m 53 94.9 1.8641 1812 Homo sp. 123 C4-7m 53 94.9 1.8641 1503 postcranial 123 C4-5m 55 98.5 1.8621 1504 postcranial 123 C4-5m 55 98.5 1.8621 1822 postcranial 123 C4-5m 55 98.5 1.8621 1505 postcranial 123 C4-5m 55 98.5 1.8621 3228 postcranial 102 C1-10m 36 36.0 1.9211 3728 postcranial 100 C2+5m 63 63.0 1.8977

Table S6. Tuned ages (according to Age model 3) of hominin fossils from the upper Burgi Member (Feibel et al., 1989; Wood, 1991). KNM-ER: National Museums of Kenya fossil accession number. Postcranial fossils presently cannot be attributed to Australopithecus or Homo. Stratigraphical level: in m above/below marker beds C4 (Feibel et al., 2009), C2 and C1.

78

Figure S1. Geological map of the Turkana Basin drainage area. The Omo River mainly drains Ethiopian Traps basalts (Tertiary Igneous), the SW rivers mainly drain Precambrian rocks. Quaternary sediments were mostly not yet present in UBU Member times. Map compiled with data from the U.S. Geological Survey. http://eros.usgs.gov/#Find_Data/Products_and_Data_Available/gtopo30/README

79 B N A

C

F E D

Figure S2. Locations in Koobi Fora Area 102 (Google Earth image), where sections A-F of the upper Burgi Member (UBU) were sampled. GPS coordinates of the sections and subsections are listed in Table S1.

Figure S3 (opposite). Tuning option Age model 1 a. Summer insolation at 65º N according to the La2004(1,1) solution (Laskar et al., 2004; Lourens et al., 2004), with positions of the Mediterranean sapropels indicated (Lourens et al., 1996). b. Dust record of Site 659 off Northwest Africa (Tiedemann et al., 1994). c. Detrended and tuned Sr isotope record from Area 102 in the Turkana Basin. Dashed lines show the proportion of Omo River water in the lake calculated with a binary mixing model. d. Hominin fossil occurrences plotted relative to wet and dry periods (vertical yellow bars) of the preces- sion-driven climate cycles. Also indicated (full circle) is the hominin site FwJj20 in Area 41 of the E Turkana Basin (Braun et al., 2010). e. Stratigraphic positions of KBS and Lorenyang Tuff layers and bC2n in the tuned Sr isotope record. Open diamond symbol = radiometric age of the KBS Tuff. f. ∂18O stack based on ODP Leg 154 sites with numbered Marine Isotope Stages (Bickert et al., 1997; Wang et al., 2010)

Figure S4 (next spread, left). Tuning option Age model 2. a. Summer insolation at 65º N according to the La2004(1,1) solution (Laskar et al., 2004; Lourens et al., 2004), with positions of the Mediterranean sapropels indicated (Lourens et al., 1996). b. Dust record of Site 659 off Northwest Africa (Tiedemann et al., 1994). c. Detrended and tuned Sr isotope record from Area 102 in the Turkana Basin. Dashed lines show the proportion of Omo River water in the lake calculated with a binary mixing model. d. Hominin fossil occurrences plotted relative to wet and dry periods (vertical yellow bars) of the precession-driven climate cycles. Also indicated (full circle) is the hominin site FwJj20 in Area 41 of the E Turkana Basin (Braun et al., 2010). e. Stratigraphic positions of KBS and Lorenyang Tuff layers and bC2n in the tuned Sr isotope record. Open diamond symbol = radiometric age of the KBS Tuff. f. ∂18O stack based on ODP Leg 154 sites with num- bered Marine Isotope Stages (Bickert et al., 1997; Wang et al., 2010)

Figure S5 (next spread, right). Tuning option Age model 4. a. Summer insolation at 65º N according to the La2004(1,1) solution (Laskar et al., 2004; Lourens et al., 2004), with positions of the Mediterranean sapropels indicated (Lourens et al., 1996). b. Dust record of Site 659 off Northwest Africa (Tiedemann et al., 1994). c. Detrended and tuned Sr isotope record from Area 102 in the Turkana Basin. Dashed lines show the proportion of Omo River water in the lake calculated with a binary mixing model. d. Hominin fossil occurrences plotted relative to wet and dry periods (vertical yellow bars) of the precession-driven climate cycles. Also indicated (full circle) is the hominin site FwJj20 in Area 41 of the E Turkana Basin (Braun et al., 2010). e. Stratigraphic positions of KBS and Lorenyang Tuff layers and bC2n in the tuned Sr isotope record. Open diamond symbol = radiometric age of the KBS Tuff. f. ∂18O stack based on ODP Leg 154 sites with num- bered Marine Isotope Stages (Bickert et al., 1997; Wang et al., 2010) 80 Age model 1

Mediterranean sapropel (s) 560 a 65N summer insolation s s s s s 520 s s 2 m / 480 W 440 b 17 9 18 1 18 3 18 5 18 7 18 9 17 7 17 3 17 5 19 1 19 3 ------i i i i i i i i i i 20.0 i ) %

( 30.0 t s

u 40.0 D 50.0 ODP 659

c Turkana -2 95% Omo contr. ) 4 -

0 -1 ed ) 1 ( d

n 90% Omo contr.

Sr 0 6 tr e 8 Sr / (d e 7 1 8 85% Omo contr. 2

d Hominin fossils FwJj20 KBS Lorenyang e Tuff layers KBS base Olduvai 3.2 f

) 3.4 ‰ ( 3.6 O 8 1 δ 3.8 68

4 62 66 70 72 64 74 Pleistocene Pliocene Olduvai

1750 1800 1850 1900 1950 2000 Age (ka)

81 Age model 2

Mediterranean sapropel (s) 560 a 65N summer insolation s s s s s 520 s s 2 m / 480 W 440 b 17 9 18 1 18 3 18 5 18 7 18 9 17 7 17 3 17 5 19 1 19 3 ------i i i i i i i i i i 20.0 i ) %

( 30.0 t s

u 40.0 D 50.0 ODP 659

c Turkana -2 95% Omo contr. ) 4 -

0 -1 ed ) 1 ( d

n 90% Omo contr.

Sr 0 6 tr e 8 Sr / (d e 7 1 8 85% Omo contr. 2

d Hominin fossils FwJj20 KBS Lorenyang e Tuff layers KBS base Olduvai 3.2 f

) 3.4 ‰ ( 3.6 O 8 1 δ 3.8 68

4 62 66 70 72 64 74 Pleistocene Pliocene Olduvai

1750 1800 1850 1900 1950 2000 Age (ka)

82 Age model 4

Mediterranean sapropel (s) 560 a 65N summer insolation s s s s s 520 s s 2 m / 480 W 440 b 17 9 18 1 18 3 18 5 18 7 18 9 17 7 17 3 17 5 19 1 19 3 ------i i i i i i i i i i 20.0 i ) %

( 30.0 t s

u 40.0 D 50.0 ODP 659

c Turkana -2 95% Omo contr. ) 4 -

0 -1 ed ) 1 ( d

n 90% Omo contr.

Sr 0 6 tr e 8 Sr / (d e 7 1 8 85% Omo contr. 2

d Hominin fossils FwJj20 KBS Lorenyang e Tuff layers KBS base Olduvai 3.2 f

) 3.4 ‰ ( 3.6 O 8 1 δ 3.8 68

4 62 66 70 72 64 74 Pleistocene Pliocene Olduvai

1750 1800 1850 1900 1950 2000 Age (ka)

83 mixing hyperbola SW catchment vs Omo water

0.7054

0.7052

Sr 0.7050 86 Sr/ 87

0.7048

0.7046

0.7044 0.70 0.75 0.80 0.85 0.90 0.95 1.00 fraction Omo water

Figure S6. Mixing hyperbola following from the binary mixing model. Blue line: mixing curve of SW rivers versus Omo River waters. The vertical part of the red rectangle covers the range of 87Sr/86Sr values measured, and the horizontal part of the rectangle indicates the concomitant fraction of Omo River water in Lake Lorenyang.

UBU Sr isotope data from E Turkana areas 0.7057

102 0.7056 Area 123 0.7055 Area 104

Area 102* 0.7054 Sr

0.7053 86 Sr/ 87 0.7052

0.7051

0.705

0.7049

0.7048

0.7047 120 110 100 90 80 70 60 50 40 30 20 10 0 Composite m level Area 102

Figure S7. Sr isotope record (87Sr/86Sr) of aquatic fossils from the composite section in Area 102 (Fig. 1, Table S2), with 87Sr/86Sr values of aquatic fossils from other areas in the Eastern Turkana Basin (Fig. 1, Table S5) plotted on the record. Area 102*: samples collected in Area 102 in 1985-1986, not in 2006 (see caption Table S5).

84 References supplementary material

Brown, F.H., Feibel, C.S., 1991. Stratigraphy, Lepre, C.J., Kent, D.V., 2010. New depositional environments and magnetostratigraphy for the Olduvai paleogeography of the Koobi Fora Formation. Subchron in the Koobi Fora Formation, In: Harris, J.M. (Ed.), Koobi Fora Research northwest Kenya, with implications for early Project, Volume 3 Stratigraphy, Artiodactyls Homo. Earth Planet. Sci. Lett. 290 (3-4): 362- and Paleoenvironments. Clarendon Press, 374. Oxford, pp 1-30. Lourens, L.J., Hilgen, F.J., Shackleton, N.J., Laskar, Faure, G., 1986. Principles of Isotope Geology, J., Wilson, D., 2004. The Neogene period. In: second ed. John Wiley & Sons, New York. Gradstein, F., Ogg, J., Smith, A.G. (Eds.), A Feibel, C.S., 1988. Paleoenvironments of the Koobi Geologic Timescale, Cambridge University Fora Formation, Turkana Basin, Northern Press, Cambridge, pp 409-430. Kenya. PhD Thesis, The University of Utah. McDougall, I., Brown, F.H., 2006. Precise 40Ar/39Ar Feibel, C.S., Brown, F.H., McDougall, I., 1989. geochronology for the upper Koobi Fora Stratigraphic context of fossil hominids from Formation, Turkana Basin, northern Kenya. J. the Omo group deposits - northern Turkana Geol. Soc. 163: 205-220. Basin, Kenya and Ethiopia. Am. J. Phys. Paillard, D., Labeyrie, L., Yiou, P., 1996. Macintosh Anthropol. 78 (4): 595-622. program performs time-series analysis. Eos 77: Feibel, C.S., Lepre, C.J., Quinn, R.L., 2009. 379. Stratigraphy, correlation, and age estimates Schulz, M., Mudelsee, M., 2002. REDFIT: for fossils from Area 123, Koobi Fora. J. Hum. estimating rednoise spectra directly from Evol. 57 (2): 112-122. unevenly spaced paleoclimate series. Comput. Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Geosci. 28 (3): 421. Correia, A.C.M., Levrard, B., 2004. A long- Wood, B.A., (Ed.), 1991. Koobi Fora Research term numerical solution for the insolation Project Volume 4, Hominid Cranial Remains, quantities of the Earth. Astron. Astrophys. 428 Oxford University Press, Oxford. (1): 261-285.

85 86 Epilogue: the evolutionary and societal relevance of aquatic resource use by hominins

Josephine C.A. Joordens

In this thesis, we propose that aquatic resources vitamin D and micronutrients such as iodine and were exploited by Homo erectus on Java (Chapter selenium, which have a strong impact on human 1), and likely by even older hominins in Africa. physiology, brain growth and development (Cun- So far, the earliest aquatic resource use (cat- nane and Stewart, 2010; Muskiet, 2010). DHA is a fish, turtle, crocodile) by hominins was found long-chain polyunsaturated fatty acid (LC-PUFA) at ~ 1.95 Ma in the Turkana Basin (Braun et al., synthesized by phytoplankton, and progressively 2010). It is, especially for very ancient hominin bio-accumulated by aquatic organisms higher up sites, difficult to establish unequivocally that in the food chain (Sargent et al. 1995; Kainz et al., hominins processed and consumed aquatic re- 2004). In contrast, DHA is rarely available (with sources. Stone tools associated with cut-marked the exception of e.g. mammalian brain tissue) or terrestrial mammalian bones demonstrate in a occurring in low amounts (e.g. in eggs) in foods straightforward way that local hominins were deriving from terrestrial ecosystems (Carlson and involved in food procurement. In contrast, cut Kingston, 2007). marks on processed fish bones are very rare, and rarely identified (Stewart, 1991; Willis et al., 2008; Modern humans can synthesize DHA from its Braun et al., 2010). Aquatic molluscan shells pose plant-derived precursor alpha-linolenic acid similar problems. When found in a cave setting (ALA) but the synthesis capacity is low: the over- together with hominin bones or tools, they pro- all efficiency of the conversion of ALA to DHA is vide evidence for hominin consumption (van Es, ~ 0.05% (Burdge and Calder, 2005; Brenna, 2010). 1930; Stiner, 1994; Marean et al., 2007; Stringer As a consequence, consumption of preformed et al., 2008). Also, conspicuous large-scale shell DHA, for instance by eating fish or shellfish, can middens, often containing tools, reliably show confer direct individual advantages with pos- hominin involvement in aquatic resource use sible evolutionary consequences. If preformed (Claassen, 1998). However, in many other cases it DHA is taken up by hominins, they do not have is difficult to distinguish between natural (physi- to synthesize DHA from ALA, thus downregulat- cal or non-hominin animal) shell accumulations, ing or eliminating a metabolically costly pathway and shells accumulated by hominin foraging ac- involving enzymes for fatty acid chain elongation tivities (Rosendahl et al., 2007). and desaturation (Brenna, 2010). Such downreg- ulation-elimination has been inferred in a Green- Why should scientists bother to look for subtle land Inuit population with a very high intake clues of aquatic resource use by early hominins? of long-chain polyunsaturated fatty acids from How relevant is it to be able to assess the relative fish and seals (Horrobin, 1987). Recently, genetic contribution of animal protein and other nutri- polymorphisms of fatty acid desaturases (en- ents derived from terrestrial and aquatic food zymes) FADS1 and FADS2 have been discovered, chains in hominin diets? Several important and with lower activities in their conversion of ALA unique characteristics of aquatic foods render it and LA (linoleic acid) to long-chain polyunsatu- worth wile to explore the potential role of aquat- rated fatty acids (see Lattka et al., 2010 for a re- ic foods in hominin evolution. Aquatic foods view). The conservation of these polymorphisms contain relatively high amounts of DHA (doco- in human populations indicates that when these sahexaenoic acid), EPA (eicosapentaenoic acid), mutations emerged they did not have negative 113 effects on survival -and may have had positive ef- uity of earliest aquatic resource use by hominins, fects-, suggesting that at that time easily obtain- and to assess the relative contribution of aquatic able preformed dietary LC-PUFA compensated for versus terrestrial food resources in hominin diet the lower LC-PUFA synthesis. (Muskiet and Kuipers, 2010; Kuipers et al., 2010).

Experimental studies on rats have shown that Is there, beyond satisfying a deep psychologi- consumption of preformed DHA led to signifi- cal need to know our origins, any societal sig- cant changes in expression of several genes in nificance in reconstructing the composition of the central nervous system (Kitajka et al., 2004) hominin resource use? What would be the impli- and promoted neurite growth in hippocampal cation of finding an ancient (millions of years) neurons (Calderon and Kim, 2004). Kawakita et systematic hominin connection with the DHA- al. (2006) have shown that dietary DHA promotes rich aquatic food chain? Recently, a whole body neurogenesis both in vitro and in vivo, and con- of literature has been drawing attention to the cluded that DHA imparts beneficial properties to role of long-chain polyunsaturated fatty acids, the function of learning and memory in rats. For in particular DHA, in human development and modern humans, Hibbeln et al. (2007) suggested health. For instance, low DHA (and EPA) status is that higher maternal consumption of seafood is implicated in coronary heart disease, inflamma- associated with better neurological development tory diseases, peri-, post-natal and major depres- of their children (verbal intelligence, prosocial sion, behavioural problems and impaired visual behaviour, fine motor, communication and social and neurological development of children (Otto development scores). et al., 2003; Krabbendam et al., 2007; Rees et al., 2009; Muskiet, 2010). These diseases and disor- Another possibly relevant and related factor may ders have a high prevalence in modern societies, be hominin maternal consumption of relatively causing major human suffering and economic high amounts of iodine and exogenous thyroid costs. Low DHA status is also related to aggressive hormone (thyroxin) from marine organisms and antisocial behaviour, and even homicide, in (Venturi and Begin, 2010). Thyroid hormone ex- Western societies (Hibbeln et al., 2004; Hibbeln erts a direct action on the expression of genes in et al., 2006). In a by now classical (double-blind, the foetal brain that are important for neurologi- placebo-controlled, randomized) trial by Gesch et cal development (Dowling et al., 2000; Chantoux al. (2002) it was shown that antisocial and violent and Francon, 2002; Zoeller and Rovett, 2004). behaviour of young adult prisoners was mark- Maternal consumption of iodine and exogenous edly reduced by supplementation with vitamins, thyroid hormones may cause heterochronic de- minerals and essential fatty acids. This outcome velopmental shifts in a foetus, precipitating phe- led to a similar study in Dutch prisons. Dietary notypic and behavioural changes with evolution- supplementation over a period of 1-3 months ary implications (Crockford, 2003, 2004, 2008). In resulted in significant reduction in incidents of rats it has been shown that hyperthyroid dams rule-breaking and aggressive behaviour by pris- (i.e. females with higher than normal thyroid oners who received nutritional supplements, hormone concentrations) have foetuses with a compared with prisoners taking placebos (Zaal- marginally higher brain weight than normal or berg et al., 2009). hypothyroid dams (Evans et al., 2002). The studies mentioned above demonstrate that The studies mentioned above demonstrate that efforts directed at establishing the composition aquatic foods contain constituents such as DHA, of hominin paleodiet are no trivial pursuit. If the iodine and thyroxin with considerable effects increasingly recognized modern human need for specifically on development and growth of brains preformed LC-PUFA in the diet (in order to stay and cognition. Consumption of aquatic food physically and mentally healthy) can be placed sources over millions of years would therefore in an evolutionary context, crucial recommenda- constitute a direct and powerful physiological tions for dietary change will carry more weight mechanism in the evolution of the hominin lin- (Joordens et al., 2007; Muskiet et al., 2007). As eage. Hence, despite the difficulties in finding Muskiet (2005) pointed out, “you are what you and interpreting subtle clues for aquatic exploita- eat, but you need to become what you ate”: in tion, it is worth the effort to establish the antiq- terms of fatty acid composition, our present-day 114 diet should be like the diet our genome originally gender and age on conversion to longer-chain evolved on. In view of present-day overfishing of polyunsaturated fatty acids. European Journal the world’s oceans, recommendations for such a on Lipid Science and Technology 107 (6): 426- dietary change should not entail a plea for con- 439. suming more fish or fish oil, but a plea for deriv- Calderon, F., Kim, H.-Y., 2004. Docosahexaenoic ing our essential long-chain polyunsaturated acid promotes neurite growth in hippocampal fatty acids (DHA and EPA) directly from cultured neurons. Journal of Neurochemistry 90: 979- phytoplankton, the green base of the aquatic 988. food chain (Arterburn et al, 2008; van Beelen Carlson, B.A., Kingston, J.D., 2007. Docosahexae- et al., 2009). Different phytoplankton species noic acid, the aquatic diet, and hominin en- produce different proportions and amounts of cephalization: difficulties in establishing evo- long-chain fatty acids. For instance diatoms yield lutionary links. American Journal of Human relatively large amounts of EPA, while flagellates Biology 19: 132-141. yield relatively large amounts of DHA (Sargent, Chantoux, F., Francon, J., 2002. Thyroid hormone 1997; Mansour et al., 2005). Culturing different regulates the expression of NeuroD/BHF1 dur- phytoplankton groups will allow production of ing development in the rat cerebellum. Molec- well-balanced long-chain polyunsaturated fatty ular and Cellular Endocrinology 194: 157-163. acid mixtures to be used as supplements to or ba- Claassen, C., 1998. Shells. Cambridge University sis of modern human food. My proposition is that Press. ultimately, phytoplankton made us human, and is Crockford, S.J., 2003. Thyroid rhythm pheno- needed to keep us humane. types and hominid evolution: a new paradigm implicates pulsatile hormone secretion in Acknowledgements speciation and adaptation changes. 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117 118 Dankwoord / Acknowledgements

“Ik denk dat de kunst vaak vaak aan de wetenschap vooraf gaat. Dat komt omdat de kunstenaar niet belemmerd wordt door de strakke regels die in de wetenschap zijn voorgeschreven.” (Dick Hillenius (1927-1987), bioloog, schrijver en dichter)

Dit proefschrift is geboren uit de kunst, en ont- ning Scholz, Matthias Glaubrecht, Anne Schulp, wikkeld in de wetenschap. Dank aan Tijs Gold- the Koobi Fora Research Project (Louise Leakey schmidt en Henri Roquas voor de inspiratie om and Meave Leakey) and the Turkana Basin In- na te gaan denken over menselijke evolutie en de stitute for co-operation and logistical support geologie van Oost-Afrika. Sinds het begin van dit in the field. Frits Muskiet, Remko Kuipers en avontuur, ongeveer 10 jaar geleden, hebben tal- Jan Wanink, dank voor inspiratie, discussie en loze mensen me geholpen om stappen te zetten nieuwe inzichten! Dank aan alle co-auteurs voor op de ingeslagen weg. Ik dank allen daarvoor, met de intensieve en goede samenwerking: Gareth name Bert van der Zwaan, Piet Oosterom, Tom Davies, Guillaume Dupont-Nivet, Craig Feibel, Veldkamp, Hans Beeckman, Auke Bijlsma en Mat- Dick Kroon, Luc Lourens, Marlijn Noback, Anne thias Glaubrecht voor hun steun in het prille be- Schulp, Mark Sier, Jeroen van der Lubbe, Hubert gin. Toen het idee verder uitkristaliseerde -door Vonhof, John de Vos en Frank Wesselingh. correspondentie en een indrukwekkend veldwerk in Turkana met Craig Feibel- kwamen Frank I thank Wil Roebroeks and the Human Origins Wesselingh, Hubert Vonhof, John de Vos en Dick Group (Faculty of Archaeology, Leiden University) Kroon in beeld. Hubert, Dick en ik schreven een for taking me on board in April 2010 and for sha- onderzoeksvoorstel dat uiteindelijk in 2005 door ring a wonderful and inspiring working environ- NWO-ALW gehonoreerd werd. Mijn onderzoek ment. I am very grateful to the reading commit- werd gefinancierd door NWO-ALW, het Dr. Catha- tee for critically reading my thesis manuscript: rina van Tussenbroekfonds, het Prins Bernhard Bert Boekschoten, Craig Feibel, Meave Leakey, Wil Cultuurfonds en de Leakey Foundation. Subsidies Roebroeks, Fred Spoor, and John de Vos. Anne voor reizen en congresbezoek werden gegeven Schulp was een baken van rust en competentie door de Universiteit Utrecht en door het Promo- in de laatste chaotische weken toen alles tegelijk vendifonds van de VU Amsterdam. af moest: dank voor de prachtige opmaak! Jeroen van der Lubbe en Jeroen van Wetten, beiden Tur- In september 2005 begon ik als promovenda aan kana-gangers, waren bereid om me bij te staan de VU en deelde met groot plezier een kamer als paranimf. Wat er ook gebeurt, zij redden de (en lief en leed) met Aafke Brader en Emma Ver- situatie: you have never let me down! steegh. Mijn dank aan alle VU collega’s voor de steun, gezelligheid en leerzame tijd! Saskia Kars, Ik heb onnoemelijk veel geleerd van mijn promo- Wynanda Koot, Wim Lustenhouwer, Suzanne Ver- tor Dick Kroon, copromotor Hubert Vonhof en degaal, Simon Jung, Gareth Davies, Onno Postma, mentor Craig Feibel. Dank voor jullie nabijheid Richard Smeets, Ron Lootens, Marin Waaijer, (ook van ver), vriendschap en vertrouwen. Martijn Klaver, Martin Konert, Pieter Vroon, John Dank aan alle vrienden, voor jullie warme be- Visser, en Bas van der Wagt boden onmisbare langstelling, steun en begrip. Tenslotte: zonder hulp bij fotografie, electronenmicroscopie, lab- mijn ouders Marc Joordens en Mariet Joordens- werk en metingen op de massaspectrometers. Wolters, mijn lief Jan Willem Dogger en onze geweldige kinderen Yann en Julie, had dit boekje I am grafeful to Rhonda Quinn, Chris Lepre, niet bestaan. Dank. Kamoya Kimeu, Halewijn Scheuerman†, Hen- 119 120