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Diet in Early Homo: a Review of the Evidence and a New Model of Adaptive Versatility

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Diet in Early Homo: a Review of the Evidence and a New Model of Adaptive Versatility ANRV287-AN35-12 ARI 17 October 2006 20:18 Diet in Early Homo: A Review of the Evidence and a New Model of Adaptive Versatility Peter S. Ungar,1 Frederick E. Grine,2 and Mark F. Teaford3 1Department of Anthropology, University of Arkansas, Fayetteville, Arkansas 72701; email: [email protected] 2Departments of Anthropology and Anatomical Sciences, Stony Brook University, Stony Brook, New York 11794; email: [email protected] 3Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; email: [email protected] Annu. Rev. Anthropol. 2006. 35:209–28 Key Words First published online as a Review in Hominin, feeding adaptations, Homo habilis, Homo rudolfensis, Advance on May 17, 2006 erectus The Annual Review of Anthropology is online at anthro.annualreviews.org Abstract This article’s doi: Several recent studies have stressed the role of dietary change in the 10.1146/annurev.anthro.35.081705.123153 origin and early evolution of our genus in Africa. Resulting models Copyright c 2006 by Annual Reviews. have been based on nutrition research and analogy to living peoples All rights reserved and nonhuman primates or on archeological and paleoenvironmen- Access provided by CASA Institution Identity on 11/11/19. For personal use only. Annu. Rev. Anthropol. 2006.35:209-228. Downloaded from www.annualreviews.org 0084-6570/06/1021-0209$20.00 tal evidence. Here we evaluate these models in the context of the hominin fossil record. Inference of diet from fossils is hampered by small samples, unclear form-function relationships, taphonomic fac- tors, and interactions between cultural and natural selection. Nev- ertheless, craniodental remains of Homo habilis, H. rudolfensis, and H. erectus offer some clues. For example, there appears to be no simple transition from an australopith to a Homo grade of dietary adaptation, or from closed forest plant diets to reliance on more open-country plants or animals. Early Homo species more likely had adaptations for flexible, versatile subsistence strategies that would have served them well in the variable paleoenvironments of the African Plio-Pleistocene. 209 ANRV287-AN35-12 ARI 17 October 2006 20:18 INTRODUCTION Homo habilis and Homo rudolfensis Over the past few years, scholars have paid Many researchers recognize two early species increased attention to the evolution of diet in within our genus, Homo habilis and H. rudolfen- the Plio-Pleistocene hominins of Africa, espe- sis (Stringer 1986, Lieberman et al. 1988, cially the earliest members of our genus, Homo Wood 1991, Rightmire 1993, Strait et al. rudolfensis, H. habilis, and H. erectus. Resulting 1997, Leakey et al. 2001, Dunsworth & models have been based largely on nutritional Walker 2002, contra Tobias 1991). For the studies combined with direct analogy (to liv- purposes of this review, we accept the hy- ing peoples or nonhuman primates) or on con- podigms set forth by Wood (1991) for textual evidence, such as archeological and pa- H. habilis and H. rudolfensis. leoenvironmental indicators. Although many Temporal ranges for these taxa are pre- of these models are elegantly constructed and sented in Figure 1. Homo habilis and H. well reasoned, they do not tell us what the rudolfensis were largely synchronous. Most hominins actually ate. They form hypotheses H. habilis specimens come from Olduvai and that may or may not be testable given the na- Koobi Fora and date to between 1.87 and ture of the fossil record. c. 1.65 Myr, although A.L. 666-1 from the Here, we review and evaluate some re- Hadar extends its range back to 2.33 Myr cent models for dietary adaptations of early (Kimbel et al. 1997). Specimens attributed to Homo in the context of the hominin fossil H. habilis at Sterkfontein (Tobias 1991) come record, the archeological record, and evidence mostly from Member 5, which probably also for environmental dynamics during the Plio- dates to between 2.3 and 1.8 Myr. Most H. Pleistocene. The most notable point from this rudolfensis specimens come from Koobi Fora exercise is the limited scope of what can ac- and date to between 1.90 and 1.85 Myr, al- tually be said about the diets of these early though specimens from the Omo Shungura hominins. Nevertheless, the jaws and teeth of Formation extend this range to 2.02 Myr and early Homo do offer some clues to the diets perhaps back even to 2.40 (Suwa et al. 1996). of these species. A synthetic view of this evi- If the UR 501 mandible from Malawi and dence, in the context of archeological and pa- KNM-BC 1 temporal from Chemeron are leoenvironmental indicators, suggests that the attributable to H. rudolfensis (Bromage et al. origin and early evolution of Homo are most 1995, Sherwood et al. 2002), this lends fur- likely associated with biological and cultural ther support to a first appearance date for this adaptations for a more flexible, versatile sub- taxon of c. 2.4 Myr. Furthermore, if KNM-ER sistence strategy. This strategy would have put 819 from Koobi Fora is H. rudolfensis (Wood the earliest members of our genus at an advan- 1991), that would extend the range for this tage given climatic fluctuation and a mosaic of taxon forward to between 1.65 and 1.55 Myr Access provided by CASA Institution Identity on 11/11/19. For personal use only. Annu. Rev. Anthropol. 2006.35:209-228. Downloaded from www.annualreviews.org different microhabitats in Africa during the (Figure 1). Even so, there is little doubt that, late Pliocene. as with other paleontological species, the fossil record does not accurately sample the entire geochronological ranges of either H. habilis or THE FOSSIL EVIDENCE FOR H. rudolfensis. PLIO-PLEISTOCENE HOMO The temporal ranges, taxonomy, and hy- podigms of early Homo species have all been Homo erectus the subject of intense debate over the past cou- Whereas Wood (1991) has argued for taxo- ple of decades, and any meaningful discussion nomic distinction of Homo ergaster from H. of the role of diet in the origin and early evo- erectus and other early Homo species, other lution of our genus must be grounded in a firm workers have noted continuous morpholog- understanding of these issues. ical variation between specimens attributed 210 Ungar · Grine · Teaford ANRV287-AN35-12 ARI 17 October 2006 20:18 Figure 1 Early Homo timeline. to H. ergaster and H. erectus (Wolpoff 1984, ria, between 800 Kyr and 600 Kyr (Geraads Kramer 1993, Rightmire 1998, Anton 2002, et al. 1986). Homo erectus has also been iden- Asfaw et al. 2002, Dunsworth & Walker tified in Member 2 at Swartkrans (Robinson 2002). We here concur with these workers, 1961, Rightmire 1990, Wood 1991, Tobias who regard the earlier and later African spec- 1991), dating to between 1.9 and 1.65 Myr imens as sampling a single evolving species, and perhaps younger (Vrba 1985, McKee et al. H. erectus. 1995). Homo erectus was a long-lived species, with a temporal range in Africa extending well over Access provided by CASA Institution Identity on 11/11/19. For personal use only. ENVIRONMENTAL DYNAMICS Annu. Rev. Anthropol. 2006.35:209-228. Downloaded from www.annualreviews.org a million years (Figure 1). It was synchronous in the earlier part of its range with both H. ha- AND DIETS OF EARLY HOMO bilis and H. rudolfensis. The oldest undisputed Given that diet is a direct link between an H. erectus specimen (the KNM-ER 2598 cra- animal and its environment, environmental nial fragment) dates to 1.89 Myr, well within dynamics likely played an important role in the ranges of both H. habilis and H. rudolfensis dietary changes related to the origin and evo- (Feibel et al. 1989). The enigmatic KNM-ER lution of early Homo. Recent investigators 3228 hipbone might extend the range of this have attempted to explain the origins of in- taxon as far back as 1.95 Myr (Susman et al. dividual hominin species by relating first ap- 1983, Rose 1984). The youngest African H. pearances of taxa during the late Pliocene to erectus fossils came from Baringo, and prob- major episodes of global cooling and drying ably date to less than 660 Kyr (Wood & (see Vrba et al. 1995). Although researchers Van Noten 1986), and from Tighenif, Alge- debate the tempo of faunal turnover at the www.annualreviews.org • Diet of Early Homo 211 ANRV287-AN35-12 ARI 17 October 2006 20:18 time (see Potts 1998), most agree that cooler mains with cut marks from Bouri, Ethiopia, and more variable climatic conditions had a dated to about the same age (De Heinzelin broad effect on mammalian diversity. Con- et al. 1999). The actual origin of material ventional wisdom associates adaptive radia- culture is almost certainly much older, how- tions of Paranthropus and Homo to these en- ever, because the earliest tools were likely vironmental changes. perishable (Mann 1972, Panger et al. 2002). Cerling (1992) has noted that after 2.5 The archeological record also likely underes- Myr, C4 grasslands spread across East Africa, timates the functional versatility of the early concomitant with periodic fluctuations in cli- hominin tool kit. The use of stone tools in mate. If any of the early hominins had crit- butchery is evinced by cut marked bones, but ical keystone foods (i.e., foods essential for tools were probably also used to process many survival and reproduction) found only in other types of foods, as is evident from mi- more closed habitats, then extinction would crowear of slightly younger Oldowan artifacts likely have followed. By contrast, if early used to prepare vegetation, presumably for hominins developed craniodental specializa- consumption, and perhaps to make other tools tions for consuming savanna resources, such from plant tissues (Keeley & Toth1981).
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