Hominin dispersals: causes, conditions, and outcomes

The ‘Out of Africa’ model that has dominated palaeoanthropology for nearly three decades was originally based on five elements: a recent ancestry to human populations; an African origin for the ancestral population; limited or no gene flow among archaic hominins and no admixture between modern humans and Neanderthals; a marked difference between the behaviour of modern humans and archaic populations; and a major role for dispersals. The first four of these have been significantly modified by accumulating fossil, genomic, and archaeological data. Dispersals, however, have remained central to the model, and have been extended to earlier phases of the evolution of Homo . Here we consider the evidence for dispersals in Pleistocene hominin evolution, and place these into the broader context of comparative evolutionary biology. We distinguish between dispersals that are essentially habitat tracking as climate or environment changes, and those conditioned by adaptive changes. Finally, we consider the consequences of dispersals for the structure of hominin populations, emphasizing the multiple potential outcomes of dispersals, the role of density dependence in structuring rates of divergence, and the role of centre‐edge models in understanding hominin diversity.