Australopithecus sediba has been hypothesized to be a close relative of the genus Homo. Here we show that MH1, the type specimen of A. sediba, was not optimized to produce high molar bite force and appears to have been limited in its ability to consume foods that were mechanically challenging to eat. Dental microwear data have previously been interpreted as indicating that A. sediba consumed hard foods, so our findings illustrate that mechanical data are essential if one aims to reconstruct a relatively complete picture of feeding adaptations in extinct hominins. An implication of our study is that the key to understanding the origin of Homo lies in understanding how environmental changes disrupted gracile australopith niches. Resulting selection pressures led to changes in diet and dietary adaption that set the stage for the emergence of our genus.
Bibliographical noteFunding Information:
This research was funded by NSF BCS 0725219, 0725183, 0725147, 0725141, 0725136, 0725126, 0725122, 0725078 and NSF DBI 0743460, the EU FP6 Marie Curie Actions MRTN-CT-2005-019564 ‘EVAN’, the South African Department of Science and Technology, the African Origins Platform, the South African National Research Foundation, the Evolutionary Studies Institute, the Palaeontological Scientific Trust, the Andrew W.
Mellon Foundation, the United States Diplomatic Mission to South Africa, the National Geographic Society, the A.H. Schultz Foundation, the Oppenheimer and Ackerman families, Sir Richard Branson and the Program to Enhance Scholarly and Creative Activities and the International Research Travel Award Grant of Texas A&M University. We thank Jackie Smilg and colleagues at the Charlotte Maxeke University Hospital for assistance in obtaining CT scans of the MH1 specimen. We thank Paul Tafforeau and ESRF for granting beam time on ID17 for experiment # EC521. Image of MH1 fossil by Brett Eloff courtesy of Lee Berger and the University of the Witwatersrand. We also thank four anonymous reviewers whose comments substantially improved our paper.