Past climate change effects on human evolution

The genus Homo evolved during the Pleistocene — an epoch of gradual cooling and amplification of glacial cycles. The changing climates influenced early human survival, adaptation and evolution in complex ways. In this Review, we present current knowledge about the effects of past climate changes on the evolutionary trajectory of human species. Humans emerged in dry grassland and shrubland when average climate conditions were warm. As global climate started cooling down, human species needed either to track their preferred habitats or to adapt to new local conditions, each of which is indicated in the archaeological record. Limited dispersal ability and narrow ecological preferences were predominant in early species, whereas cultural innovations and consequently wider ecological niches became commonplace in later species, allowing them to live in colder extratropical climates. Yet, despite their growing ecological versatility, all species but one eventually went extinct. Future research should explore cultural transmission between and within species, and the influence of climate change on human genetic diversification.