Human evolution: Climate restrictions influenced migrations out of Africa

Climate influenced the timing and routes available to Homo sapiens as they migrated out of Africa, a Nature Communications study suggests. The research, which highlights the role of palaeoclimate variability in modern human dispersals, could aid our understanding of Homo sapiens’ evolutionary story.

It is accepted that early humans migrated out of Africa, but due to a scarcity of relevant fossils and ancient DNA, the timings and routes of their expansion into Eurasia are contested.

Robert Beyer, Andrea Manica and colleagues use paleoclimate reconstructions and estimates of the minimum amount of rainfall required by hunter-gatherers to survive, to evaluate when, and where, expansions out of Africa might have been facilitated by favourable weather conditions and wet corridors into Eurasia. The estimated timings and routes suggested by their simulations are compatible with archaeological and genetic evidence, suggesting multiple migrations out of Africa may have occurred over the last 300,000 years. The authors suggest that challenging environmental conditions in southwest Asia, the intermittent arrival of humans from Africa, and possible competition with other hominins, may explain the failure of early waves of Homo sapiens to settle permanently in Eurasia before a larger, highly successful wave of migration, around 65,000 years ago.

The authors conclude their research demonstrates when it would have been climatically feasible for Homo sapiens to migrate from Africa. However, further research is needed to explore whether these opportunities were seized.