EARLY HOMINID HABITAT PREFERENCES IN EAST-AFRICA - PALEOSOL CARBON ISOTOPIC EVIDENCE

Interpretations of the habitat preferences of sympatric Homo and Austr alopithecus have been based mainly on regional and/or macrohabitat rec onstructions of the Plio-Pleistocene environment. Microhabitat reconst ructions are biased by the preservation of many East African sites in disturbed fluvial contexts and by the rarity of organic remains that m ay provide site-specific evidence of habitat diversity. In order to de termine early hominid foraging behavior and land-use patterns, however , their site-specific floral microhabitat use must be reconstructed ac ross the Plio-Pleistocene landscape. Variability in the distribution a nd density of excavated archaeological traces over a paleolandscape ma y be related to hominid activities, resource use, and habitat preferen ce. The stable isotopic composition of paleosol (buried soil) organic and pedogenic carbonate carbon can be used to estimate the original pr oportion of grasses (C4) to woody (C3) vegetation, and is a powerful t ool for microhabitat reconstruction. In collaboration with a landscape archaeology project, isotopic values were determined on basal Bed II paleosol samples from trenches excavated at Olduvai Gorge (Tanzania). Interpreted with reference to modern East African soil and vegetation analogs, carbon isotopic ratios indicate a 1 km2 area near HWK and FLK in the eastern paleolake Olduvai margin supported a riparian forest t o grassy woodland approximately 1.74 Myr ago. Stone artifacts and hamm erstone-fractured bones are abundant across the waxy claystone paleoso l, which corresponds to level 1 at HWK-E. Isotopic evidence from this preliminary study (including FLK Zinjanthropus) suggests Plio-Pleistoc ene hominids in East Africa may have preferred relatively closed woodl and habitats that may have offered food, shade, and predator and sleep ing refuge.