The Water Optimisation Hypothesis and the human occupation of the mid-latitude belt in the Pleistocene

A hypothesis - the Water Optimisation Hypothesis - is proposed to predict the occupation of sites by Homo. The hypothesis proposes that Homo occupied intermediate positions in the humidity spectrum. A consequence is that many suitable areas coincided with semi-arid to sub-humid rainfall regimes. Homo should therefore have located its sites in relation to water sources. Analysis of 357 sites occupied by Homo between 200,000 and 10,000 years ago confirms the prediction and reveals no difference in behaviour between Homo sapiens sapiens and the Neanderthals (H. s.neanderthalensis), indicating that the water-attachment of sites is a universal feature of the genus. It is proposed that a belt of similar characteristics, sometimes severed by climate, stretched from south-west Iberia to south-east Australia and was the cauldron of modern human evolution. Geographical expansion of Homo is predicted to have followed river courses and, only occasionally, coastlines.