Fig. 4.

Cenozoic uplift chronology, climatic conditions, paleoenvironment, and early hominin evolution. Paleoaltimetric data (diamonds) of Early to Middle Miocene onset of uplift correlate with major climatic and environmental shifts. Data compilation as follows: onset of volcanism and rifting in Kenya (47); Miocene sea-level fluctuations (48); global deep-sea oxygen isotopes, including the Miocene climate optimum (27); vegetation shifts based on carbon isotopes from herbivore teeth (X_f percentile δ¹³C values for fossil populations) (45) and pollen data (42) in north Kenya; pan-African rain forest expansion–isolation events (26) and savannah expansion (44); and early primates and bipedalism in northern Kenya (37, 38, 49).