Figure 1.

Data for all the South African hominins are summarized as means δ¹³C (black boxes) and standard deviations compared with means and standard deviations for the browsing and grazing fauna. The sites are given in sequence from oldest (top) to youngest (bottom). Makapansgat Member 3 is about 2.7–3 Ma, Sterkfontein Member 4 is usually considered to be about 2.2–2.5 Ma and Swartkrans Member 1 is younger than 2 Ma. These ages based on biostratigraphy are imprecise, but sufficient for our purposes. More precise chronometric studies based on Pb/U isotopes have recently been completed (R. Pickering 2009, personal communication), but do not change the overall sequence. All the hominin data show significant C₄ contributions compared with C₃ feeders, in spite of large shifts, from closed to open, in the environments (Reed 1997). Adapted from Lee-Thorp & Sponheimer (2006).