<P> Endocranial casts of Homo habilis and Homo erectus differ in the organisation of the frontal lobe, in particular in the prefrontal cortex where higher mental functions of consciousness and abstraction occur . By themselves, mental capacities have likely played a role in the success of Eurasian colonisation . They would have allowed for greater social complexity, predation and sharing prey, and an overall higher quality diet . If we are to believe Bednarik and his seafaring Indonesian Homo erectus, then the brain must have played a role in crossing channels . </P> <P> According to Wheeler, loss of functional body hair would have helped prevent hyperthermia, since hair will obstruct air flow over the skin and restrict cooling by evaporation . He further suggests that body cooling due to hair loss has relieved a thermal constraint on brain size (but in a response to Falk's radiator hypothesis, Ralph Holloway maintains that there is no evidence for a temperature constraint on brain size). However, differences in body hair between Homo habilis and Homo erectus are impossible to test, and it will remain unclear whether hair loss was part of the hominin adaptation or preadaptation to Eurasia . </P>

What is the major difference between the apes and the early hominins