The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)


Miombo woodlands and early hominins: A comparison of carbonate stable isotope data from modern Koobi Fora and 3.97Ma Allia Bay fauna

MELANIE M. BEASLEY and MARGARET J. SCHOENINGER.

Department of Anthropology, UC, San Diego

March 26, 2015 1:30, Grand Ballroom C Add to calendar

The ecological niche exploited by early hominins is assumed to have played an essential role in the origins of bipedalism, a distinguishing characteristic of hominins. Reconstructing the paleoenvironment at early hominin sites is essential for understanding the selective forces that resulted in such a significant morphological change. This study focuses on Allia Bay, Kenya (site 261-1, 3.97 Ma) where Australopithecus anamensis, the earliest obligate biped, is found associated with fossil hippos, elephants, giraffes, suids, deinotheres, and bovids. An early pilot study (Schoeninger et al., 2003, JAA 22:200-207) suggested that the region was more mesic than today with an environment similar to modern miombo woodlands. Here we present new bulk stable carbon and oxygen isotope data of tooth enamel of 50 fossil fauna from Allia Bay and bone carbonate from 156 modern fauna collected within the larger Koobi Fora basin. After applying correction factors (i.e., Suess effect, converting bone to enamel values), the fossil fauna have lower oxygen values and lower carbon isotope values compared to the modern fauna. The carbon isotope data may indicate minor diagenetic alteration (Schoeninger et al., 2003, IJO, 13:11-19), which we are currently investigating further with new analytical techniques. The oxygen isotope data indicate a wetter paleoenvironment with more tree cover compared to the modern Koobi Fora basin. Our results support the proposal that selection for bipedalism in Au. anamensis originated in an environment similar to modern miombo woodlands, which are wetter than the modern day Koobi Fora basin.