Recent Research Into Oldowan Hominin Activities at Kanjera South, Western Kenya

Afr Archaeol Rev DOI 10.1007/s10437-006-9006-1 ORIGINAL ARTICLE

Recent Research into Oldowan Hominin Activities at Kanjera South, Western Kenya

L. C. Bishop · T. W. Plummer · J. V. Ferraro · D. Braun · P. W. Ditchﬁeld · F. Hertel · J. D. Kingston · J. Hicks · R. Potts

C Springer Science+Business Media, Inc. 2006

Abstract This paper presents the initial results of excavations at Kanjera South, located on the Homa Peninsula in Western Kenya. Since 1995, our exploration of this locality has yielded a combination of artefacts and well preserved faunal remains in a sedimentary context that also allows for environmental reconstruction. Here we examine the history of exploration of Kanjera and its significance in the development of palaeoanthropological research in East Africa. We also summarise our findings from the recently discovered Oldowan site. Taphonomic analyses suggest that the archaeological layers were formed at least partially by hominin activity. Artefacts made from a wide variety of raw materials are abundant, as are animal bones. Results of our first analyses confirm that Oldowan hominins had considerable behavioural flexibility and occupied a range of habitats. Cet article presente« des resultats« preliminaires« de nos fouilles au site de Kanjera South, situesurlap« eninsule« de Homa au Kenya occidental. Depuis 1995 nos explorations a` cette localite« ont produit une combinaison des outils lithiques et des restes fossils dans un bon etat«

L. C. Bishop () School of Biological and Earth Sciences, Liverpool John Moores University, Liverpool, Byrom Street, Liverpool L3 3AF, United Kingdom e-mail: [email protected]

T. W. Plummer Anthropology Laboratory, Kissena Hall, Queens College, CUNY, New York, USA

J. V. Ferraro Department of Anthropology, University of California, Los Angeles, USA

D. Braun Department of Anthropology, Rutgers University, New Jersey, USA

P. W. Ditchfield Research Laboratory for Archaeology and the History of Art, University of Oxford, Oxford, United Kingdom Springer Afr Archaeol Rev de conservation venant d’un contexte sedimentaire« qui permet egalement« les reconstitutions paleoenvironnementaux. Ici nous examinons l’histoire de l’exploration de Kanjera et de son importance dans le developpement« de la recherche paleoanthropologique en Afrique de l’Est. Nous recapitulons« egalement« nos resultats« du gisement recemment« decouvert« d’Oldowan. L’etude« taphonomique suggere` que les couches archeologiques« ont et« eform« ees« au moins partiellement par l’activite« des hominins. Les objets fabriques« faits a` partir d’une grande variet« edemati« eres` lithiques sont abondants, de memeˆ que les os animaux. Les resultats« de nos premieres` analyses confirment que les hominins d’Oldowan ont eu une flexibilitede« comportement considerable« et ont occupe« une gamme d’habitats differents.«

Keywords Kenya . Plio-Pleistocene . Early Stone Age . Oldowan . Hominin behaviour . Palaeoenvironments

Introduction

Kanjera South is part of the Kanjera site complex, situated on the Homa Peninsula. It is located between the two branches of the East African Rift Valley on the southern margin of the Winam Gulf of Lake Victoria, SW Kenya (Fig. 1). The peninsula is dominated by the Homa Mountain carbonatite complex, active from the late Miocene into the Pleistocene (Le Bas, 1977). Fluvial-lacustrine sediments were deposited on the flanks of the mountain intermittently over the last 6 million years (Ma) (Behrensmeyer et al., 1995; Ditchfield, Hicks, Plummer, Bishop, & Potts, 1999; Plummer, Bishop, Ditchfield, & Hicks, 1999). The locality of Kanjera is well known to researchers looking at the history of Eastern Africa. There is a documented history of palaeoanthropological research and exploration in the area from at least 1911, when the region was first visited by Oswald (1914). Fossils, in- cluding those of hominids, have been collected in the area throughout most of the last century (Plummer & Potts, 1995). Mammalian paleontological collections have included the type specimens of the cercopithecid Theropithecus oswaldi (Kanjera), the suids Nyanzachoerus kanamensis (Kanam West) and Metridiochoerus andrewsi (locality unrecorded), the giraffid Giraffa jumae (Rawi) and the gomphotherid Anancus kenyensis (Kanam East). Perhaps the most significant events in the history of exploration at Kanjera were LSB Leakey’s expeditions in 1932Ð1935, which revealed fragments of four anatomically modern hominins associated with Pleistocene mammal fossils on the surface of the site (Leakey, 1935; Plummer & Potts, 1995). Kanam West, a nearby locality, yielded a hominin mandible

F. Hertel Department of Biology, California State University, Northridge, California, USA

J. D. Kingston Department of Anthropology, Emory University, Atlanta, Georgia, USA

J. Hicks Denver Museum of Nature and Science, Department of Earth and Space Sciences, Denver, Colorado, USA

R. Potts National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, Division of Palaeontology, National Museums of Kenya, Nairobi, Kenya Springer Afr Archaeol Rev

Fig. 1 Location of the Homa Peninsula in Kenya and a partial topographic map showing the Northern, Middle and Southern Exposures of Kanjera (Behrensmeyer et al., 1995,Fig.2) fragment (Pickford, 1987). Leakey, Reck, Boswell, Hopwood, & Solomon (1933) and Leakey (1935) suggested that the Kanam hominin was from early Pleistocene sediments, which in conjunction with the Kanjera hominins from what he took to be middle Pleistocene sediments, supported the view that modern human morphology had considerable antiquity. This claim was challenged by Boswell (1935), who argued that associations between the hominins and much earlier fauna at both Kanam and Kanjera were spurious and caused by mixing of fauna from different geological strata. Springer Afr Archaeol Rev

Boswell’s (1935) conclusions did little to enhance the reputation of either Leakey or Kanjera, but this seems not to have deterred future research at the site. Subsequent expeditions to the area by Pilbeam (1974) and Pickford (1984) recovered many fossils and Acheulian, Middle Stone Age (MSA) and Late Stone Age (LSA) artefacts. Work at Kan- jera continued with expeditions by a Smithsonian Institution team co-directed by Potts and Plummer beginning in 1987 (Plummer & Potts, 1989) These excavations, like most previous work at the site, focussed on the early and middle Pleistocene Northern Exposures at Kanjera (Plummer, 1992).

Current research at Kanjera

Our discoveries in the Southern Exposures of Kanjera challenge previous ideas about the scope and antiquity of the site. Sediments in the Southern Exposures were initially thought to be coeval with the sediments in the Northern Exposures. In 1995, Oldowan artefacts and Plio-Pleistocene faunal elements were surface collected from Kanjera South. These finds were followed by a programme of test pits that revealed several rich layers of artefacts and fauna. Fieldwork in 1996 and 1997 refined the geology and geochronology of the Kanjera Formation (South) and documented the context and nature of the Oldowan archaeological occurrences (Plummer et al., 1999; Ditchfield et al., 1999). Subsequent field seasons in 2000 and 2001 expanded the fossil and artefact samples and refined our picture of hominin activities in Kanjera South.

Geology

The Kanjera Formation contains fossils and artefacts and crops out in the Northern, Mid- dle and Southern Exposures (Fig. 1) which are approximately 0.5 km apart. Lithological differences between sediments in the North and in the South are indicated by separate bed designations, KN for the North and KS for the South. Fluvio-lacustrine sediments, 12 m thick, are divided into six beds designated KS1-KS6, from oldest to youngest. Magneto- and biostratigraphy indicate that sedimentation began in the late Pliocene (Fig. 2). The Olduvai subchron (1.95Ð1.77 Ma) in Beds KS-5 and KS-6 overlies the artefact and fossil bearing levels in Beds KS-1 to KS-3. Sediments at Kanjera South were deposited in a lake-margin setting, with palaeoflow directed towards the depositional low to the North (Behrensmeyer et al., 1995; Ditchfield et al., 1999). KS-1 is a sandy silt to fine sand, with occasional pebble and granule lenses. It was probably deposited in a marginal lake plain environment. KS-2 has two facies, a fine, pebbly sand (KS-2 PS) and a thin, patchy conglomerate (KS-2 CP). These were deposited by an ephemerally flowing system of small shallow channels with diffuse flow. The KS-2 PS was deposited by relatively gentle flow, whilst the KS-2 CP conglomerate represents episodes of more rapid (perhaps sheet) flow. KS-3 is a sandy silt with occasional lenses of conglomerate, again deposited in shallow channels. Poor to moderate palaeosol formation indicates that stable land surfaces formed during depositional hiatuses. Oldowan artefacts and fauna have been found from the top of KS-1 through KS-3, with dense concentrations of archaeological materials in KS-2 and KS-3. Preliminary faunal analyses and stable isotopic analysis of palaeosol carbonates indicate that Kanjera South was a relatively open, grass-dominated habitat during the deposition of Beds KS-1 through KS-3 (Plummer et al., 1999). Springer Afr Archaeol Rev

Fig. 2 Summary plot of the magneto- and biostratigraphy of the Kanjera Fm (S). Filled circles and dark bands in the column represent magnetically normal intervals. Open circles and white bands in the column represent intervals of reversed magnetic polarity (Timescale after Brain, 1981). The best match for normal band B+ is the Olduvai Subchron (Plummer et al., 1999)

Excavations

Beginning in 1996, taphonomically controlled excavations have been carried out over four field seasons at Kanjera South. Two large excavations (Excavations 1 and 2) and three small excavations (Excavations 5, 6 and 7) were placed along a 70 m transect of outcrop (Fig. 3). Excavation 1 is the largest, now covering an area of approximately 175 m2. Excavation 2 is 15 m2 and the smaller excavations are each 4 m2. Artefacts and fossil fauna were recovered from each of the five excavations. Object density was highest in the two largest excavations. A meter thickness of sediment from Excavation 1 has yielded approximately 3,000 fossils and 4,000 artefacts. Each recovered object was given three-dimensional coordinates using a Topcon Laser transit. Thousands of additional objects were recovered through sieving and spit bags and have provenance to square meter and 5-cm spit. Preliminary results from this excavation will be discussed further below. Many of the finds from Excavation 1 derive from KS-1 and KS-2; some overlying KS-3 had eroded away. In contrast, the Excavation 2 archaeological sample derives al- most entirely from KS-3. The remains recovered include a complete hippopotamus pelvis with five articulated vertebrae, ribs and a canine tooth in direct spatial association with five flakes. A complete hippopotamus femur was recovered from the same microstratigraphic level in Excavation 1, and may be a dispersed element from the hippopotamus in Excavation 2. Artefacts associated with an array of isolated bovid and equid fossils were recovered below the hippopotamus skeleton in Excavation 2.

Preliminary Results

Excavations were stopped temporarily in 2001 to allow for cleaning and preparation of the recovered objects. Preparation took place in laboratories at the National Museums of Kenya over 2 years. Fossil bones and teeth are frequently well preserved, but due to the high levels Springer Afr Archaeol Rev

Fig. 3 Excavations at Kanjera South. Locations of the numbered excavations are shown on a topographic map of the Southern Exposures. Results from Excavation 1, the largest excavation, are presented in this paper of free carbonates in local ground water, finds were often covered with carbonate nodules and other concretions. Thus far we have completed most of the taxonomic and skeletal part identifications of the fauna recovered. A preliminary report of the lithic analysis can also be summarised here. Except for the conglomerate occurrences, water flow was not the main agent of accumu- lation of the Kanjera archaeological materials (Plummer et al., 1999). In the lower part of the sequence, particularly KS-2 and KS-3, there is a clear spatial relationship between the artefacts and fauna. Sedimentary clast size and orientation analyses reveal that many objects are outsized clasts relative to grain size and objects show no preferred orientation. Skeletal part analysis shows that all skeletal parts are represented. Systematic study of bone modification and damage is still underway. During our initial analysis of the fossil bone, both hominin and carnivore damage have been noted. Some fossil and artefact refits have also been identified. The high concentration of artefacts and fauna, some of which exhibit hominin modifications, in association with abundant Oldowan artefacts, suggest that hominins were at least partially responsible for collecting and processing the archaeological fauna. Taxonomic identification of the piece-plotted fauna from Excavation 1 (n = 1343) has produced a diverse faunal list (Table 1). Over 99% of the faunal assemblage recovered from Excavation 1 consists of mammalian fossils. The vast majority of these (88%) are antelopes (Mammalia: Bovidae) (Table 2). Horses (Equidae) and pigs (Suidae) are the next most abundant mammals. All regions of the skeleton are represented. Of 1,649 bones identifiable to skeletal part, cranial elements make up 37%, vertebrae and ribs 16%, girdle elements Springer Afr Archaeol Rev

Table 1 Faunal list Cercopithecidae Cercopithicinae indet.∗ Theropithecus oswaldi∗

Carnivora Carnivora, size 2∗ Felidae, size 3 Crocuta sp.∗

Suidae Metridiocheorus andrewsi Metridiochoerus modestus∗ Kolpochoerus sp.

Hippopotamidae Hippopotamus, size 6∗

Bovidae Tragelaphini, size 3∗ Tragelaphus cf. scriptus Tragelaphus, size 2 Bovini∗ Reduncini, size 1Ð3∗ Kobus sp.∗ Alcelaphini, size 2 and 3∗ Antilopini, size 1 and 2∗ Antidorcas cf. recki∗

Equidae Equus sp.∗ Note. ∗ Numerous mammalian Hipparionine fossils have been recovered from Kanjera South. This table shows Rhinocerotidae indet∗ the taxa to which identiﬁable specimens have been assigned. ∗ Proboscoidea An asterisk ( ) indicates taxa Elephantidae, indet.∗ previously reported from Deinotherium sp. Kanjera.

7% and limbs 40%. The broad representation of the different parts of the skeleton suggests that some relatively complete carcasses were originally introduced to the site. Remains of frequently immature size 1 and 2 mammals (Brain, 1981) are numerous in comparison to zooarcheological samples from slightly younger sites from Bed I Gorge, Tanzania (Potts, 1988). We are currently testing the hypothesis that hominins secured early access to at least some of these individuals.

Lithic technology

Numerous stone artefacts have also been recovered from the excavations at Kanjera South. The Homa Peninsula has a heterogenous geology reﬂected in the diversity of raw materials in the Kanjera South artefact assemblage. Although many artifacts were made from locally available sources, such as ﬁne grained basic igneous rocks and fenitized rocks from the Homa Mountain carbonatite complex, a suite of metamorphic and sedimentary rocks were also utilized. Many artefacts were made from rocks that were not present in the Kanjera Springer Afr Archaeol Rev

Table 2 Identiﬁable Fauna from Excavation 1

Taxonomic group NISP Percent (%)

Bovidae 1179 87.79 Equidae 131 9.75 Suidae 14 1.04 Primates 5 0.37 Carnivora 4 0.30 Hippopotamidae 4 0.30 Rodentia 3 0.22 Rhinocerotidae 2 0.15 Proboscidea 1 0.07 N = 1343 100.00

Note. The taxon, number of identifiable specimens (NISP) and percentage remains identifiable to each are shown. Note the overwhelming majority of identifiable specimens are attributed to the antelope family, the Bovidae.

South drainage during the Plio-Pleistocene. An extensive sourcing project is underway to determine the primary and secondary sources of artefact raw materials. The technological systems at Kanjera South may show stark contrasts with other Oldowan sites. Pliocene Oldowan sites often exhibit high frequencies of unifacial forms at Gona (Semaw, 2000;Semaw,etal.,2003) or bipolar cores at Omo Shungura (Chavaillan, 1976; Merrick, 1976; Marrick & Marrick, 1976; Howells et al., 1987). Preliminary technological analyses at Kanjera South have shown that radial and discoidal techniques were often employed. Technological variability within the assemblage may follow raw material divisions (Fig. 4). The raw material diversity of the Kanjera South assemblage provides a unique opportunity to understand differential levels of raw material utilization in the Oldowan. Preliminary evidence for intensive utilization of stone resources comes from techniques that were possibly designed to extend the use life of cores (e.g. core rejuvenation ﬂakes). Some

Fig. 4 An artefact from Kanjera South. Core made on a rhyolite flake, from KS-2 within Excavation 1. (Field Number KJS 16184a). Drawing by Simon Hounsell Springer Afr Archaeol Rev raw materials show many flakes from later reduction stages (flake types IVÐVI in Toth, 1985, 1987). It is possible that some raw materials were flaked prior to transport to the Kanjera South site. Overall the assemblage is characterized by a diversity of artifact types and raw materials.

Conclusion

Excavation 1 at Kanjera South provides the ﬁrst substantial Pliocene site assemblage of associated Oldowan artefacts and archaeological fauna outside Olduvai Gorge, Tanzania. Preliminary results suggest differences in palaeoenvironmental setting, faunal usage and lithic technology from other Oldowan sites. A diverse assemblage of fossils shows evidence of interactions between hominins and the fauna, with carnivores also contributing to bone surface damage. The lithic technology recovered from the excavations shows a variety of core production modes (Roche, 2000). Analyses of all aspects of the recovered materials are ongoing. However, even these initial ﬁndings indicate that Kanjera South has great potential to increase our understanding of the range of behaviour of Oldowan hominins.

Acknowledgments We thank the Office of the President, Republic of Kenya and the National Museums of Kenya for permission and support to conduct the field and laboratory studies described here. The research was conducted under the co-operative agreement between the National Museums of Kenya and the Smithsonian Institution. Funding for this research has been provided by the National Science Foundation, the National Geographic Society, the Wenner-Gren Foundation, the L.S.B. Leakey Foundation and the Boise Fund. Logis- tical support was provided by the Human Origins Program of the Smithsonian Institution. LB would like to acknowledge the support of NERC and the Nuffield Foundation. Thanks to Jim McCloskey for help with the preparation of the figures.

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