Current events

Sally McBrearty Variability in traces of Middle Department of , Pleistocene hominid behavior in the University of Connecticut, Storrs, Connecticut 06269, U.S.A. Kapthurin Formation, Baringo,

Laura Bishop Department of Human Anatomy and Cell Biology, University of Liverpool, Liverpool L69 3BX, U.K.

John Kingston Department of Geology and Geophysics, , New Haven, Connecticut 06520, U.S.A. Journal of (1996) 30, 563–580

Introduction and background New research in the Kapthurin Formation, Kenya, suggests a greater degree of variability in hominid behavior during the late Middle Pleistocene than has previously been suspected. The Middle Pleistocene commences with the shift from reversed to normal magnetic polarity at about 780 ka, and ends at the beginning of the last interglacial, at approximately 130 ka (Butzer & Isaac, 1975; Imbrie & Imbrie, 1980; Berger et al., 1984; Martinson et al., 1987; Cande & Kent, 1992; Baksi et al., 1992). Homo erectus was replaced in Africa around 500 ka by hominids termed archaic Homo sapiens. Anatomically modern H. sapiens is represented by fossil evidence dating to ca. 130 ka from East Africa and by fossils dating to at least 90 ka from South Africa (Day & Stringer, 1982; Stringer & Andrews, 1988; Grün & Stringer, 1991; Foley & Lahr, 1992; Deacon, 1993). Statistical principles suggest that known age range is in part a function of sample size, and it has been empirically demonstrated that expanded sample sizes can affect first and last appearance data for both vertebrate and invertebrate fossil taxa, including hominoids (Strauss & Sadler, 1989; Marshall, 1990; Springer, 1990; Hill, 1987; Flynn et al., 1995). Due to the extremely small size of the early anatomically modern H. sapiens sample, it is unlikely that the dates of 130 ka or 90 ka represent the true first appearance of modern humans in Africa. Evidence for the processes leading to the last major event in human evolution, the origin of modern humans, must therefore be sought in the late Middle Pleistocene. A conspicuous late Middle Pleistocene archaeological event in Africa is the end of the Earlier (ESA) and the beginning of the (MSA). The ESA Acheulian disappeared, giving way to more diverse MSA traditions. K–Ar dates at the site of Gaddemotte, Ethiopia, indicating that the MSA occurrence there may be as old as 180 ka (Wendorf et al., 1975) have been widely cited, although it is possible that the MSA has even greater antiquity (Evernden & Curtis, 1965). The Kapthurin Formation itself provides one of the few reliable datum points for the age of the terminal Acheulian. Here late Acheulian artefacts are capped by a tuff dated by K–Ar to 240–250 ka (Tallon, 1978). Because stone tools are the products of hominid behavior, examining the shift from Acheulian to MSA technology is useful in showing how hominid adaptations changed

0047–2484/96/060563+17 $18.00/0  1996 Academic Press Limited 564 .  ET AL. coincident with the replacement of H. erectus by H. sapiens, and perhaps ultimately in clarifying the of the speciation event itself. The Acheulian contains large bifaces, while the MSA is characterized by smaller tools, often made on flakes struck from prepared cores. Because both early H. erectus (H. ergaster of Wood, 1992) and the Acheulian industry appeared in Africa between 1·7 and 1·8 Ma (Feibel et al., 1989; Roche et al., 1994), it is tempting to see the two events as linked. An examination of the later record, however, shows no clear association of hominid taxon with archaeological industry. Archaic H. sapiens fossils have been found associated with Acheulian, Sangoan, and MSA artefacts at various sites (Mturi, 1976; Mehlman, 1984, 1987); MSA artefacts are also known to occur with the remains of anatomically modern H. sapiens (Singer & Wymer, 1982). At some sites, industrial variants such as the Sangoan, characterized by heavy duty tools, or the ‘‘Fauresmith’’ containing small bifaces, appear to follow the Acheulian proper and to precede the MSA (Volman, 1984; McBrearty, 1987). These industrial variants have been linked to broad physiographic regions of Africa and their implied paleohabitats. Thus the Sangoan has long been considered a forest or woodland adaptation, while the ‘‘Fauresmith’’, has been thought confined to savanna zones (Clark, 1964, 1965, 1972, 1982, 1988), although the possible role of lithic raw material in determining artefact form has long been noted (e.g., Humphreys, 1979). An expansion of geographic range in the MSA and accompanying regional diversification has been thought to illustrate the improved adaptive abilities of early H. sapiens over those of H. erectus (Clark, 1970, 1988, 1992). Two assumptions are central to the prevailing view of African hominid behavioral change during the late Middle Pleistocene: (1) the Acheulian is fairly uniform, typologically and technologically, throughout its spatial and temporal range, in contrast to the MSA which presents a variety of artefact types and manufacturing techniques. (2) Different terminal Acheulian and MSA industries are found in distinct widely separated geographic regions (Clark, 1970, 1988, 1992). Our work in the Kapthurin Formation leads us to question these assumptions. Having relocated and reexamined 13 previously reported sites and discovered 28 new sites, we find that: (1) there is unequivocal variability among roughly contemporary assemblages throughout the sequence, whether they be termed ESA or MSA. (2) Assemblages that can be assigned to industries formerly thought to be confined to distinct biogeographic zones are found at sites no more than 4 km apart. The Kapthurin Formation also provides evidence for possible signs of modern behavior at an early date. Despite the presence in Africa of anatomically modern human fossils before 100 ka, undisputed evidence of modern human behavior at this time depth has thus far been sparse (Klein, 1989, 1992; Clark, 1992), although convincing signs of precocious have recently been described for MSA sites in Zaire (Brooks et al., 1995; Yellen et al., 1995). In Europe, the blade-based industry accompanies the arrival of modern humans ca. 45 ka (White, 1982; Klein, 1989; Mellars, 1992). Because of the simultaneous appearance of blades and modern humans in the later Pleistocene record of Europe, and because blade production is a more efficient use of lithic raw material than flake production, blades are often treated in the literature as a unique modern human innovation. In fact, the origins of blade production appear more complex. Although most European Middle industries are flake-based, it is now realized that assemblages from a number of European sites, dating to between ca. 90 ka and ca. 115 ka, have a significant blade component (Révillion & Tuffreau, 1994; Conard, 1990). Blades are also known from the pre-Augignacian industry of coastal North Africa (McBurney, 1967), which   565 has been thought to date to about 80–60 ka (Clark, 1992), but is probably substantially older. The Amudian industry of the Levant contains both blades and bifaces (Garrod & Bate, 1937; Jelinek, 1982). Electron spin resonance (ESR) dates from Tabun (Grün & Stringer, 1991) indicate that the Tabun Amudian may date to as much as 200 ka, whereas TL dates recently announced by Mercier et al. (1995) suggest a possible antiquity for the Amudian of as much as 300 ka. Elongated flakes present at the Acheulian site of Latamne in Syria are thought by Clark (1967) to presage the laminar technology of the Amudian. In Africa, blades are clearly present very early. Although the frequency of blades in the Howiesonspoort industry of South Africa has attracted much attention (e.g., Ambrose & Lorenz, 1990; Parkington, 1990), it is often overlooked that the makers of South African MSA industries routinely manufactured blades from a variety of core types (Sampson, 1972, 1974; Volman, 1984). The South African MSA, as a whole, is poorly dated; the earliest MSA levels at Klasies River Mouth probably date to 100–130 ka (Deacon, 1993), but South African MSA technology no doubt has its beginnings substantially earlier (Volman, 1984). Our work confirms the observations of Leakey et al. (1969) that blades occur with Acheulian bifaces in the Kapthurin Formation and demonstrates that the roots of African blade production penetrate deep into the Middle Pleistocene. In the Kapthurin Formation, prismatic blades are securely dated by K–Ar to >240 ka (Tallon, 1978).

The Kapthurin Formation The Kapthurin Formation forms part of the sedimentary sequence in the Tugen Hills, a complex tilted fault block about 75 km long, lying on a roughly N–S axis in the floor of the Kenya Rift west of Lake Baringo (Figure 1). The Kapthurin Formation is exposed over an area of about 150 km2, and the best known sections are found in drainages of the Ndau, Kapthurin, and Chemeron Rivers. It was divided by Martyn (1969) into five major units (K1 through K5; Figure 2), and the stratigraphy further refined by Tallon (1976, 1978). Kapthurin sediments range from coarsely bedded boulder conglomerates to fine grained volcanic tuffs. Both fluvial and lacustrine facies are represented, and paleosols imply a series of intermittently stable landsurfaces. Artefacts and fossil fauna and flora are found throughout the sequence. With estimated thicknesses of 125 and >150 m (Tallon, 1978; Martyn, 1969) the Kapthurin Formation represents a substantial span of geologic time. The Ndau trachymugearite, dated at 1·57 Ma (Hill et al., 1986), lies near the top of the underlying Chemeron Formation, and provides a maximum age for Kapthurin rocks. Tallon (1978) and Cornelissen et al. (1990) report conventional K–Ar dates for the pumice tuff (K2), a thick conspicuous marker horizon near the base of the middle part of the formation. These dates, corrected for new constants using formulae provided by Ness et al. (1980, range from 620&6to890&260 ka. The pumice tuff is normally magnetized (Dagley et al., 1978; Cornelissen et al., 1990), suggesting that it is younger than 780 ka. We have yet to encounter fossils or artefacts below the pumice tuff (K2), and thus, all material reported here appears to be <780 ka in age. The bedded tuff (K4) in the upper part of the formation has been dated by Tallon (1978) to 250&120 and 240&8 ka. The latter dates are frequently cited as the age of the African terminal Acheulian. The remains of at least two hominid individuals have been found in the Kapthurin Formation by previous workers. Both hominid localities lie in the middle part of the Formation, below the grey tuff (Figure 2). A young adult mandible (KNM-BK 67; Leakey et al., 1969), was a surface find. Two hominid phalanges, a right metatarsal, and a fragmentary right

566 Kobosowany B • KERIO RIVER • LHA • • F • 0KM10 18 F ' C 29 • BK67 B B N ' • Mugoyuwoni 19 • • KABARNET 20 TRACK 14 • 16 FS • • TUGEN HILLS 25 13 17 JKS MS  • • . • • 2 •  BK8518 4 • • LS  C •  • • C ' 12 Kipchere 21 •

• 3 Bartekero Kamego 22 • Chemeron D 15 ' Kapthurin •

Ndau

• 6 TAL ET TRACK • A E 7 ' •

Kapthurin • 5 . 1 • D 24 • • MARIGAT 36 D 10 ° KENYA • 0 23 11 NAIROBI Map area ' E • BARINGO 500m 0 LAKE E • 30 0 ° 30 ' N N   567 ulna (KNM-BK 63-66; Solan & Day, 1992) were subsequently discovered in excavation. A second more robust adult mandible (KNM-BK 8518) was found in situ at the nearby site of GnJh-19 (Van Noten, 1982; Van Noten & Wood, 1985; Wood & Van Noten, 1986). Wood & Van Noten (1986), noting the lack of diagnostic criteria for mandibular and dental remains within the genus Homo (cf. Rightmire, 1990), assign the two mandibles (KNM-BK 67 and 8518) to Homo sp. indet. (aff. erectus), though subsequently Wood (1991) has included them in H. erectus (sensu Wood, 1992; i.e., not H. ergaster). Stringer (1993), however, refers them to archaic H. sapiens. The mandibles resemble archaic specimens such as the Mauer mandible in features of tooth size, root morphology, and shape of the ramus and symphysis (Ward, personal communication), but overlap between the ranges of H. erectus and archaic H. sapiens in these features renders specific attribution dubious. The grey tuff is undatable by conventional K–Ar, and its age is critical to that of the Kapthurin hominids. One aim of the present project is to improve chronometric control for the formation by the application of single crystal laser fusion (SCLF) 40Ar/39Ar dating, a method with a higher degree of analytical precision than conventional K–Ar (e.g., Deino & Potts, 1990). Preliminary analyses of the grey tuff suggest detrital contamination, but a limited number of cognate crystals present have proven datable by SCLF 40Ar/39Ar. Analyses of larger samples will determine if our preliminary dates indicate the age of the eruptive event (Deino, personal communication). Leakey et al. (1969) reported stone artefacts from three sites in the Kapthurin Formation, but some confusion has arisen because the described material comes from different stratigraphic levels. Their assemblages include unusual ovate handaxes, often unifacial or with minimal ventral trimming, made on large flakes struck from prepared cores, as well as the distinctive large blade component. Although a team directed by Van Noten has reported the discovery of 22 archaeological and paleontological sites from the formation (Cornelissen et al., 1990), only one of these (GnJh-17) is described in any detail (Cornelissen, 1992). At GnJh-17 an assemblage containing handaxes, picks, and casual and Levallois cores, associated with a sequence of paleosol development, was recovered from sediments below the bedded tuff (K4), dated by K–Ar to ca. 240–250 ka (Tallon, 1976, 1978). We have observed the large blades reported by Leakey et al. (1969) at several localities in this part of the section.

The 1993 season With very few exceptions, site documentation was not available for localities reported by previous workers. However, in 1993 we successfully relocated and re-examined 13 previously reported sites (see Table 1). In seeking new sites, work was initially concentrated upon the vicinity of the Kapthurin River and its tributaries the Bartekero and Kobosowany, and in the adjacent Mugoyuwoni drainage, because these areas were known to be productive. Toward the end of the season we began to prospect a formerly unexplored area of Kapthurin exposures in the Chemeron River drainage in the southeast of our research area. Altogether our efforts resulted in the discovery of 28 new archaeological and paleontological sites (Table 1). At some sites, material was found in situ; at others it occurs in surface context. Sites range from small

Figure 1. Map of Kapthurin Formation. Archaeological and paleontological localities discovered or relocated in 1993 are indicated by numbers. Letters indicate sites discovered by previous workers. Symbols D–D*, etc., indicate geologic sections measured in 1993. Section A–A* was measured on the left bank of the main Kapthurin channel, about 2 km upstream (west) of its confluence with its tributary, the Kobosowany. 568 .  ET AL.   569 surface scatters (ca. 10 m2) to larger fairly dense concentrations (ca. 500 m2); at five sites there are two distinct superimposed artefact or fossil bearing stratigraphic units. Tuffaceous marker beds allow us to establish rough contemporaneity among sites (Figure 3), and geochemical analysis of tuffs will refine these field correlations. Identifiable fossil fauna and representative artefacts were collected from all sites; at four sites we carried out controlled surface collections. Our total collection from all sites numbers in excess of 1500 stone artefacts (Figures 4 and 5) and 300 vertebrate fossils (Table 2). The newly documented Kapthurin Formation sites are distributed throughout the section (Figure 2), with the exception of the lowest unit (K1). The most promising of them may be grouped into four stratigraphic intervals: (1) within the pumice tuff (K2); (2) within the lacustrine facies of the lower middle silts and gravels (K3*); (3) in the middle silts and gravels immediately below the grey tuff [K3(ii)]; and (4) within or immediately below the bedded tuff and its probable lateral equivalent [K3(iii) and K4]. In the pumice tuff (K2) we found one in situ occurrence, Loc. 19 (GnJh-54), where megafaunal bones, elephant teeth, and remarkably fresh stone flakes and cores [Figure 4(a)] are buried in the pumice tuff on either side of the deeply incised Kobosowany river channel. We expect very precise age estimates for the pumice tuff from SCLF 40Ar/39Ar analyses. Ten sites are found within K3*, a series of red and black sands and clays in the eastern part of the Kapthurin Formation exposures (see Figure 1). The sediments containing the artefacts and fauna appear to be lacustrine in origin; they are cut through in several places by sandy paleochannel features. Paleosols and root casts suggest intermittent subaerial conditions, perhaps due to fluctuating lake levels. Fossil vertebrates are overwhelmingly aquatic and include hippopotamus, fish, crocodile, and turtle. Stone artefacts with few exceptions are unretouched flakes struck from casual, single platform, multiplatform, or radial cores made on small basalt cobbles [Figures 4(b) and (c)]. Controlled surface collections were carried out at two promising sites, Locs. 7 and 23 (GnJh-42 and GnJh-57). Our preliminary mapping indicates that the sites are underlain by the pumice tuff (K2) and overlain by the grey tuff and the upper Kasurein basalt; thus they date to between ca. 780 ka and ca. 500 ka. They underlie the Acheulian assemblages in the bedded tuff (K4) and are separated from them by >80 m of section (see Figures 2 and 3). Thirteen localities in the middle part of the formation immediately below the grey tuff [K3(ii)] exhibit superb faunal preservation. It is here that previous researchers have recovered hominid fossils, and our 1993 expedition produced a remarkable array of vertebrate remains (Table 2). Geologically, most fossils recovered by us in 1993 seem to be associated with small fluvial channel features and a series of paleosols. Our samples include cercopithecine and colobine monkey teeth, rodent specimens ranging from teeth of the cane rat to a complete skull, dentition, and partial postcranial skeleton of a large porcupine (Hystrix), and various cranial and postcranial carnivore specimens, including a complete viverrid (Ichneumia) skull with dentition. Suids, bovids, and hippopotamids are numerous. Specimens representing species such as Oryx indicate open, even arid, conditions; others, such as Kobus, suggest a closed

Figure 2. Generalized stratigraphic section of the Kapthurin Formation showing stratigraphic location of archaeological and paleontological localities discovered by this expedition (numbers) and previous workers (letters). Key: J1b, lower Kasurein basalt; K1, lower silts and gravels; K1*, lower clay facies; K2, pumice tuff; K2a, Lake Baringo Trachyte; K3(i), lower middle silts and gravels immediately above K2; K3(ii), middle silts and gravels immediately below grey tuff; gt, grey tuff; K3(iii), upper middle silts and gravels between grey tuff and K4; K3*, middle silts and gravels (lacustrine) facies; K4, bedded tuff; K5, upper silts and gravels; H, hominids. 570 .  ET AL.

Table 1 Kapthurin Formation 1993 site inventory

McB SASES Geological Loc. (GnJh) unit Material Context

1 — K3(ii) Fauna Surface 2 38 K3(ii) and K4 Fauna and arts Surface, in situ 3 39 K3(ii) Fauna and arts Surface, in situ 4 — K3(ii) Fauna Surface 540K3* Fauna and arts Surface 641K3* Fauna and arts Surface 7* 42 K3* Fauna and arts Surface 8 43 K3(ii) Fauna and arts Surface, in situ 9 44 K3(i) Fauna and arts Surface 10 45 K3* Fauna and arts Surface 11 46 K3* Fauna and arts Surface 12 47 K3(ii) Fauna and arts Surface, in situ 13 48 K3(ii) Fauna and arts Surface, in situ 14 49 K3(iii) or K4 Fauna and arts Surface 15 50 K3* Fauna and arts Surface, in situ 16 51 K3(iii) Artefacts Surface 17 52 K3(iii) Fauna and arts Surface, in situ 18 53 K3(i) Fauna and arts Surface, in situ 19 54 K2 Fauna and arts Surface, in situ 20 55 K3(ii) Fauna and arts Surface 21 — K3(ii) Fauna Surface 22 56 K3(ii) or K3(iii) Fauna and arts Surface 23 57 K3* Fauna and arts Surface 24 — K3* Fauna Surface 25 58 K3(ii) or K3(iii) Fauna and arts Surface, in situ 26 59 K3(iii) Fauna and arts Surface 27 GoJh-4 K3(ii), K3(iii) or K4 Fauna and arts Surface 28 GoJh-5 K3(iii) Fauna and arts Surface, in situ 29† 60 K3 Fauna and arts Surface 30 61 K3* Fauna and arts Surface JKS 20 K3(ii) Fauna and arts Surface, in situ LS 23 K3(ii) Fauna and arts Surface, in situ MS 24 K3(ii) Fauna and arts Surface EKG HOM K3(ii) Fauna and arts Surface LHA LIV K3(iii) and K4 Fauna and arts Surface, in situ FS FAC K3(iii) Fauna and arts Surface A 15 K3(iii) and K4 Fauna and arts Surface, in situ B 16 K3(iii) Artefacts Surface C 17 K3(ii), K3(iii) and K4 Fauna and arts Surface, in situ D18K3* Fauna Surface RL GnJi-28 ?K4? Fauna and arts Surface, in situ

Note: paleontological sites without artefacts are not assigned a SASES number. KEY: K2, Pumice tuff; K3, Middle silts and gravels; K3(i), Lower middle silts and gravels, immediately above K2; K3(ii), Middle silts and gravels, immediately below grey tuff; K3(iii), Upper middle silts and gravels, above grey tuff, below bedded tuff;K3*, Middle silts and gravels, (lacustrine) facies; K4, Bedded tuff. *Probably equivalent to Tallon’s locality 1/2012. †Equivalent to BPRP locality K126. habitat with a nearby contemporary source of water. Rodent fossils are many and diverse. Most have thus far been identified to the generic level only, and most genera represented are known to include species with a wide array of habitat preferences, from arid savanna to woodland and wet grassland. However, the presence of both the cane rat (Thryonomys) and E' K4

F' B'

K4 C' D' K4 K4 Covered

Upper Kasurein Basalt

A'A'  

0

K2 Covered F 10 Covered

Covered 20 m C Covered Lithology legend

Covered Claystone Loc. 6 Covered Siltstone Fine sandstone K2 Covered Medium sandstone K2 Coarse sandstone B Conglomerate Tuff Loc. 7 Lower Basalt Kasurein Paleosol A Basalt Pedogenic carbonate E Tuffaceous sediment Diatomite

D Limestone 571 Figure 3. Kapthurin Formation geologic sections measured in 1993. Locations of measured sections are indicated in Figure 1. 572 .  ET AL.

b a c

d f

g

e 0 5 cm

Figure 4. Artefacts collected from the Kapthurin Formation, 1993. (a) Radial core, in situ K2, Loc. 19; (b) casual core, K3*, Loc. 15; (c) multiplatform core, K3*, Loc. 11; (d) prismatic opposed platform blade core, K3(iii), LHA; (e) double struck Levallois core, ?K4, Rorop Lingop; (f) small biface, ?K4, Rorop Lingop; (g) broad unifacial foliate point, ?K4, Rorop Lingop. swamp rat (Otomys) seems to indicate local areas of dense grassy cover. The modern taxon Otomys angoniensis is found in the grassy fringes of rivers and swamps, whereas the giant pouched rat Cricetomys today inhabits forest and thicket settings, including those adjacent to river channels in Baringo District (Kingdon, 1974; Nowak & Paradiso, 1983; Hill, personal communication). Archaeologically this part of the section is enigmatic, and excavations by previous workers have produced few artefacts. We observed isolated flakes and cores in situ at   573

a

b c

0 5 10 cm Figure 5. (a) Ovate ‘‘uniface’’ on large Levallois flake, K3(iii), LHA; (b) opposed platform tabular Levallois blade core, K3(iii), exposures above Loc. 6; (c) pick/chopper, bifacial, untrimmed butt, K3(iii), Loc. 16. several newly discovered sites, but their relation to the fossils is ambiguous, and it is as yet unclear what, if any, role was played by hominids in accumulating the fossil bone. Ten sites discovered in 1993 lie high in the section below the bedded tuff [K3(iii)]; at four of these, material also occurs within the bedded tuff (K4) itself. The K3/K4 contact has been portrayed as a formerly stable landsurface (Cornelissen et al., 1990; Cornelissen, 1992), and it displays pronounced paleosol development. One aspect of our current work is the reconstruc- tion of the ancient vegetation through isotopic analysis of paleosol carbonates, particularly those from K3(iii) and K4. The archaeological sites that received most attention from previous workers are in this part of the section, including the ‘‘Leakey handaxe area’’ (LHA), a site 574 .  ET AL.

Table 2 Fauna from the Kapthurin Formation

Gastropoda Melanoides sp. Pisces Tilapia sp. *Clarias sp. Reptilia Crocodilia Crocodylus sp. Chelonia Squamata Lacertilia Varanidae Varanus sp. Ophidia Aves Struthioformes Struthio sp. Mammalia Rodentia Cricetidae Dendromurinae *Dendromus sp. *Steatomys sp. Cricetomyinae *Cricetomys sp. Glyridae *Graphiurus sp. Hystricidae *Hystrix sp. Muridae Oenomys sp. *Otomys cf. angoniensis Thryonomyidae Thryonomys sp. Insectivora *Soricidae Primates Cercopithecidae Colobus sp. Cercopithecus sp. Papio sp. Theropithecus cf. oswaldi Homo cf. erectus Carnivora Felidae Panthera leo Hyaenidae Crocuta crocuta *Viverridae Ichneumia sp. Proboscidea Elephantidae Elephas sp. Hyracoidea Procaviidae Heterohyrax sp. Perissodactyla Rhinocerotidae Ceratotherium simum Artiodactyla Suidae Kolpochoerus majus Phacochoerus aethiopicus *Potamochoerus porcus Hippopotamidae Hippopotamus amphibius Bovidae Alcelaphini Alcelaphus cf. buselaphus Alcelaphus sp. *Damaliscus sp. Antilopini *Gazella sp. Bovini *cf. Syncerus caffer Cephalophini Antidorcas sp. Cephalophus sp. *Sylvicapra sp. Hippotragini *Oryx sp. Neotragini *Ourebia sp. Reduncini Redunca sp. Kobus cf. ellipsiprymnus *Kobus sp. Tragelaphini Tragelaphus cf. scriptus *Tragelaphus sp. Tubulidentata Orycteropodidae Orycteropus sp.

Material collected in 1993 plus identifications compiled from Leakey et al. (1969), Tallon (1978), Hill et al. (1986), Van Noten et al., (1987), Harris & White (1979) and Cornelissen et al. (1990). *Taxa previously unknown from the Formation. complex reported by Leakey et al. (1969), where blades and the characteristic unifacial ovate handaxes [Figure 5(a)] are present. An unpublished assemblage from the site of GnJh-15, excavated under the direction of Van Noten in the early 1980s, also contains blade debitage. From examination of material collected by previous workers and by ourselves in 1993, it can   575 be observed that some of the Kapthurin blades are produced by direct percussion with hard hammer from single and opposed platform tabular cores, some with carefully prepared platforms, as part of a Levallois reduction sequence [Figure 5(b)]. Others are struck from prismatic blade cores with either single or opposed platforms [Figure 4(d)]. All are executed in basalt. We performed a controlled surface collection at LHA, and located a promising in situ artefact locality in the same part of the section to the south at Loc. 17 (GnJh-52) in the Mugoyuwoni drainage, where heavy duty implements lend the assemblage a Sangoan-like appearance [cf. Figure 5(c)]. Because the bedded tuff (K4) is thick, distinctive, and resistant to erosion, it is possible to trace it laterally where it overlies the middle silts and gravels (K3) in the main area of Kapthurin Formation exposures, and thus to correlate sites here temporally. Immediately to the north, however, the upfaulted Lake Baringo trachyte creates a different topography. Tallon (1976, 1978) describes a tuff lying on the surface of the Lake Baringo trachyte as the lateral equivalent of the bedded tuff (K4). At the site of Rorop Lingop (GnJi-28), about 4 km north of the Kapthurin River, numerous artefacts of a quite distinct industry are preserved within this tuff. Rorop Lingop artefacts include small bifaces [Figure 4(f)] considered characteristic of ‘‘Fauresmith’’ or terminal Acheulian industries elsewhere. Present also are foliate points, both unifacial and bifacial, typical of the MSA [Figure 4(g)], and radial and Levallois cores [Figure 4(e)]. Our preliminary geochemical analyses indicate that the Rorop Lingop tuff can be equated with the bedded tuff (K4), but more intensive sampling is needed to clarify precisely the relative stratigraphic positions of sites in this part of the section.

Discussion These results provide us with a number of directions for future research. The artefacts from the lacustrine sediments of K3* are extremely interesting. Although our small collection contains few retouched pieces, many archaeologists would refer the material to the MSA on technological grounds. While some of the casual cores recall choppers [e.g., Figure 4(b)], radial and opposed platform cores more closely resemble MSA examples. The artefacts appear to date to between ca. 780–500 ka. This age estimate exceeds most previous maximum estimates for MSA material (e.g., Wendorf et al., 1975) by as much as half a million years, but is substantially younger than the classic Oldowan sequences at Olduvai Gorge or . These materials confirm the existence of a flake-based, biface-free industry contemporary with Acheulian occurrences elsewhere (cf. Clark, 1992). It is perhaps significant that, as is the case at Olduvai Gorge (Leakey, 1971; Hay, 1976) and Olorgesailie (Potts, 1989), this small flake industry is found in a lakeshore environment. However, in the Middle Awash region of Ethiopia (Clark et al., 1994), it appears that a Middle Pleistocene flake-based industry is found in a fluvial rather than a lacustrine context (Schick, personal communication). Our ongoing geochemical work and SCLF 40Ar/39Ar dating will establish the age of this Kapthurin material more precisely, and our analysis of excavated artefact samples will determine its affinities. The blades from the upper part of the Kapthurin Formation are important in their undisturbed context and incontrovertible early age. They predate the earliest blades yet known from the European Middle Paleolithic by 125 000 years, and those from the European by least 200 000 years. If the new TL dates of Mercier et al. (1995) from Tabun are accurate, the Kapthurin blades are roughly contemporary with the Amudian in the Levant. The association of blades with Acheulian artefacts is significant, as in Africa blades are usually considered a Middle or Later Stone Age phenomenon. The Kapthurin blades are clear 576 .  ET AL. evidence of their makers’ technical sophistication and their mastery of recalcitrant raw materials. Current evidence may suggest the repeated independent invention or rediscovery of blade production in the prehistoric Old World, or much more complex patterns of technological exchange among hominid populations than is currently envisaged. Another possible interpretation is the existence of a second stream of technical knowledge that persisted alongside conventional flake production methods, and that provided an alternate technical mode to be used as the need and opportunity arose. In any case, standardized procedures of blade production were known to some hominids groups as early as the Middle Pleistocene, and the Kapthurin Formation provides the earliest securely dated evidence for this technology in Africa. The relatively small geographic area studied by us in 1993 contains elements of at least three, and possibly four, distinct and roughly contemporaneous lithic industries dating to approximately 240–250 ka. The material from LHA, with its unifacial ovate handaxes [Figure 5(a)], is usually referred to the terminal Acheulian. At other sites (GnJh-15, GnJh-17, GnJh-51), Sangoan-like picks or core axes are present [Figure 5(c)]. The collection from Rorop Lingop (GnJi-28) contains small bifaces typical of ‘‘Fauresmith’’ assemblages, together with points and Levallois debitage characteristic of MSA industries [Figure 4(e), (f), (g)]. In the past, the Sangoan industry was thought to be found only in the more densely wooded regions of Africa, and the ‘‘Fauresmith’’ in more open habitats. In the Kapthurin Formation, assemblages containing distinctive Sangoan and ‘‘Fauresmith’’ elements are found at sites no more than 4 km apart, suggesting that they are not confined to widely separated biogeographic zones. Our ongoing isotopic analyses of paleosol carbonates will produce a clearer picture of paleovegetation at Kapthurin sites. Acheulian, Sangoan, ‘‘Fauresmith’’, and MSA industries have also been variously interpreted as successive entities, activity variants, or reflections of the properties of different lithic raw materials. We would point out that multiple hominid lineages, including archaic H. sapiens, anatomically modern H. sapiens, and perhaps late survivors of H. erectus, may have been present in East Africa in the late Middle Pleistocene, and that interactions among hominid groups may contribute to the Kapthurin Formation’s archaeological variety. The Kapthurin Formation provides the opportunity to examine the evolving nature of topography, plant and animal communities, and hominid behavior in a local Rift Valley setting over the span of at least half a million years. Our future work will furnish data enabling us to choose between competing explanations for the observed hominid behavioral patterns preliminarily described here.

Acknowledgements This research was funded by a research grant to Sally McBrearty from N.S.F. (DBS-9213775). It was carried out under a permit issued by the Office of the President of Kenya to the Baringo Paleontological Research Project (BPRP), a joint project of the National Museums of Kenya (NMK) and Yale University, under the direction of Andrew Hill. Thanks are due to Mohammed Isahakia, NMK director, to Hélène Roche, head of the NMK Division of , and to Meave Leakey, head of the NMK Division of , for facilitating the project. BPRP members Andrew Hill, Barbara Brown, Steven Ward, Alan Deino, and Bonnie Fine Jacobs, and NMK personnel John Kimengich, Kiptalam Cheboi, and Boniface Kimeu provided invaluable help and support in the field. Rodent specimens were kindly identified by Alisa Winkler of the Shuler Museum of Paleontology,   577

Dallas, and by Christiane Denys of the Muséum National d’Histoire Naturelle, Paris; fossil fish by Kathlyn Stewart of the Canadian Museum of Nature, Ottawa. Thanks are due to Els Cornelissen, Pierre-Jean Texier, Kathy Schick, Mike Mehlman, and Alison Brooks for stimulating discussion, and to two anonymous reviewers for useful advice. Andrew Hill also provided invaluable, though sometimes intolerable, comments on the MS.

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