On the Road to China: The Environmental Landscape of the Early Pleistocene in Western Eurasia and Its Implication for the Dispersal of Homo

Abstract

Many adaptations of the genus Homo have been attributed to the expansion savanna environments in East Africa during the past 5 million years. It has been hypothesized that this expansion of savanna habitats northward into the Levant as well as eastward into India and China in the Late Pliocene/Early Pleistocene is the impetus for Homo, as well as other African taxa, to ­disperse out of Africa. Paleoecological reconstructions based on the identification of grazing taxa and ecological diversity analyses have supported models that favor the role of extrinsic forces in the dispersal of early hominins. However, critical analysis of Indicator Species and Ecological Diversity Analysis methods of paleoecological reconstructions suggest that their application to higher latitude sites may not provide robust results. Community-wide taxonomic analysis for western Eurasian sites suggests that the ‘Ubeidiya, Dmanisi and the Orce basin sites are most similar to Mediterranean and temperate woodland and differ from African savanna. While Mediterranean and temperate biomes include a mixture of both open and closed habitats, there is no evidence for the presence of subtropical savannas of African origin. Key ecological factors such as temperature, precipitation and seasonality differ between the northern latitudinal region and East Africa. This suggests that grassland habitats present in northern latitudes may have provided a novel environment for dispersing hominin populations. This supports the intrinsic model of ‘Out of Africa I’, and the variability selection hypothesis in particular.