Evolutionary Geography and the Afrotropical Model of Hominin Evolution

During the second half of the twentieth century, the evidence that Africa was central to hominin evolution became overwhelming. The earliest occurrences of most of the fossil hominin taxa and lithic technologies are to be found in Africa, and there is also strong evidence that humans are closely related to African apes, and that the genetic origins of modern humans lie in Africa. The aim of this article is to consider the possible evolutionary and ecological basis for this — why should Africa be so central? After considering biases in the record that might promote an African record, this article uses evolutionary geography – the spatial and distributional properties of the evolutionary process — to consider the factors that lead to higher rates of speciation, novelty and dispersals, as well as the way in which the African ecological context is structured and changes through time. Critical factors identified are the variable role of the Sahara, the different extent of the Afrotropical realm as climate changes, the impact of basin structure, and the effect of variable topography and surface water distribution. The key factor is biogeographic regionalisation and the shared evolutionary histories that reflect this. It is proposed that hominin evolution is globally part of the Afrotropical realm and its history, and that biogeographical variation within Africa is a key to understand the diverse nature of African hominins and their potential to disperse beyond the continent. More broadly, this article shows the importance of placing hominin evolution into a comparative and theoretical framework, particularly evolutionary geography, and proposes a more general basis for the Afrotropical Model of Hominin Evolution.