Stepping out: a computer simulation of hominid dispersal from Africa.

A succession of new discoveries and the recent application of new dating methods provide strong evidence that Eurasia was colonized soon after 2.0m.y.a. In light of this new evidence many scenarios have been proposed regarding the influence of glacial/interglacial cycles on hominid dispersal, the role of mountain chains and deserts as barriers, the significance of land bridges and the possibility of sea-crossings. Such factors have been proposed to explain the apparent early arrival of hominids in East Asia and relatively late arrival in Europe, although the evidence in both regions remains open to various interpretations. While it is relatively easy to propose environmental factors that may have influenced dispersal patterns, it is more difficult to evaluate such proposals and to establish what the combined impact of several factors might have been. Moreover, the role of historical contingency in creating the observed pattern of dispersal has yet to be considered. This paper describes a computer simulation model of hominid dispersal which seeks to provide a means to evaluate environmental and ecological factors in hominid dispersal. It creates probability distributions for arrival dates at six key localities and compares these with current estimates from the archaeological and fossil records. It uses these to support some of the current arguments about dispersal and to challenge others.