Stable isotope-based diet reconstructions of Turkana Basin hominins

Hominin fossil evidence in the Turkana Basin in Kenya from ca. 4.1 to 1.4 Ma samples two archaic early hominin genera and records some of the early evolutionary history of Paranthropus and Homo. Stable carbon isotopes in fossil tooth enamel are used to estimate the fraction of diet derived from C-3 or C-4 resources in these hominin taxa. The earliest hominin species in the Turkana Basin, Australopithecus anamensis, derived nearly all of its diet from C-3 resources. Subsequently, by ca. 3.3 Ma, the later Kenyanthropus platyops had a very wide dietary range-from virtually a purely C-3 resource-based diet to one dominated by C4 resources. By ca. 2 Ma, hominins in the Turkana Basin had split into two distinct groups: specimens attributable to the genus Homo provide evidence for a diet with a ca. 65/35 ratio of C-3- to C-4-based resources, whereas P. boisei had a higher fraction of C-4-based diet (ca. 25/75 ratio). Homo sp. increased the fraction of C-4-based resources in the diet through ca. 1.5 Ma, whereas P. boisei maintained its high dependency on C-4-derived resources.