Monday, July 25, 2011

Paranthropus boisei: Cow-Man of the Pleistocene?

The elusive cow-man
Lots of anthropological research focuses on figuring out what our ancestors ate. One long-standing question concerns the diet of robust australopithicines, a group of three species of early hominin that most researchers place together in the genus Paranthropus. These three species share a suite of adaptations of the teeth, jaws and cranium which all relate to extremely powerful chewing. The consensus among researchers has been that Paranthropus species ate a diet of hard objects (e.g. nuts or hard fruits), or perhaps a difficult-to-process diet of tubers and other undergrouund plant storage organs.  

A new carbon isotope study reported in this article in PNAS by Cerling and colleagues argues that P. boisei subsisted on C4 vegetation like grass and sedges, not on hard objects (hence the cow photo). This is consistent a previous study of dental microwear by Ungar et al. of which found no evidence for hard object feeding in P. boisei.  This result is surprising, as several dental microwear studies of the southern African robust hominin P. robustus are consistent with hard object feeding in this species, and carbon isotopes for robustus show much more C3 plant use (C3 vegetation comes from bushes and trees, including fruit). Thus, it appears that there may have been considerable dietary diversity within this genus, with P. boisei having diverged from a more "traditional" primate diet to focus on grazing. 

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