This should be a good read:
Understanding Climate's Influence on Human Evolution
The hominin fossil record documents a history of critical evolutionary
events that have ultimately shaped and defined what it means to be
human, including the origins of bipedalism; the emergence of our genus
Homo; the first use of stone tools; increases in brain size; and the
emergence of Homo sapiens, tools, and culture. The Earth's geological
record suggests that some evolutionary events were coincident with
substantial changes in African and Eurasian climate, raising the
possibility that critical junctures in human evolution and behavioral
development may have been affected by the environmental characteristics
of the areas where hominins evolved. Understanding Climate's Change
on Human Evolution explores the opportunities of using scientific
research to improve our understanding of how climate may have helped
shape our species.
