ABSTRACT
Hominins are great apes with distinctive features for surviving a drier climate of grassland and savannah, rather than woodland. They have an erect posture, an ability to move on two feet and larger brains. There were once many different types of hominins but we represent the only surviving species. Bigger brains and bodies point to changes in lifestyle, and there are other new features that suggest primate evolution was now emphasising a more flexible approach. The shoulder could perform throwing, the lower body allowed long-distance running and hominin teeth could now eat meat as well as vegetation. It seems likely that it was the geological upheavals in the Rift Valley that drove the evolution and dispersal of bigger-brained non-specialist primates. Although a bigger body extends travel opportunities, the advantage of a bigger brain is more questionable. Given the expense of neural tissue in terms of energy, some serious justification is needed.
