Fig. 2.

The δ¹³C values of African fossil hominin (A) and cercopithecid (B) tooth enamel and (C) soil carbonate and leaf wax C₃₀-acid and (D) the percentage of grass pollen from eastern Africa. Published fossil hominin and cercopithecid δ¹³C data are from refs. 1, 2, 4, 14, 16–29, and 31–34. Soil carbonate δ¹³C values are plotted as means for 100-ky age bins to view long-term trends but are also plotted for individual soils from the Omo-Turkana, Afar, and Laetoli regions (9, 37, 41, 42, 56–65); ages are assigned as in original publication or using the assignment provided in ref. 66. Mean leaf wax δ¹³C values (C₃₀ n-alkanoic acids) for 100-ky bins and percentage of grass pollen from the Deep Sea Drilling Project Site 231 are from refs. 38 and 40. Fossil ages are plotted as midpoints if the age constraint is a range of dates. In A−C, more positive δ¹³C values indicate an increase in the contribution of C₄ vegetation. In C, error bars are 1σ on the mean.