East Africa were highly variable. This may have driven hominin
speciation and also subsequent dispersal events. The pulsed climate
variability hypothesis should be seen as a framework, which describes
the palaeoclimate context within which early human evolution
occurred. It does not, however, provide a mechanism
through which the evolutionary process occurred and geographic
separation, environmental stress, accelerated evolution and
extinction of generalist verses specialists, variability selection, and
inter-species competition could all have played a role. It should also
be remembered that climate may not have always been the underlying
cause and that intrinsic social factors may have played a
significant role especially with increased encephalisation (Flinn
et al., 2005). However, it does seem that an understanding the
role of East African palaeoclimates is required to explain why and
when hominin species evolved and eventually migrated out of East
Africa.