Figure 1.
Top panel shows the East African Rift valley lake variability shown both as the number of Basin containing deep or shallow lakes and the calculated normalised lake index.
The putative hominin dispersals ‘D’ (red arrows out of Africa, dotted within Africa only) are shown above. Middle panel shows African hominin species diversity over time. Bottom panel shows hominin brain estimates for Africa and Eurasia. Hominin specimen dates and brain size estimates were taken from Shultz et al [3]. East African hominin diversity at each 100 kyrs interval were estimated using first (FAD) and last appearance dates (FAD) from the literature [2], [35]–[36], [46]. Homo erectus and H. ergaster were treated as a ‘super-species’ referred to in the Figure key and text as ‘Homo erectus (sensu lato)’, but distinct regional processes in brain size change were identified by separating the specimens by continent in the analyses. Hominin migration dates were estimated by FAD of hominin specimens outside of EARS. Lake variability index was calculated by collating the published geological evidence for the appearance of either deep ephemeral or shallow alkaline lakes in seven major Basins [15], [17], [23]–[27], [34]–[37]. The index was normalised by dividing by 7 to produce a range from 0 to 1.
Figure 2.
Relative impact on model fit of different paleoclimate indicators as predictors of aspects of African hominin evolution (species turnover, brain size change, dispersal events, and overall diversity).
Values represent the deltaAIC change [38] from dropping each of the indicators from the global model. ODP721 was not incuded in the migration analyses due to a high VIF. Non-climate variables included in these models are not shown here as they vary across analyses but can be found in File S1.
Table 1.
EARS lake activity is predicted by regional paleoclimate records.
Table 2.
Lake presence and Mediterranean dust records predict hominin dispersal and diversity patterns (0–3 Ma).
Table 3.
The relationship between time and EARS lake coverage and encephalisation in hominins in Africa and Eurasia.