人類の進化：アフリカからの移動に先立つ、人間の生息域の大幅な拡大

The major dispersal of humans out of Africa around 50,000 years ago was preceded by an increase in diversity of the habitats that humans chose to live in, according to new research published in Nature. This expansion could have provided ancient humans with the ecological flexibility to succeed in new environments, providing further insights into human migrations.

Current genetic evidence indicates that contemporary Eurasian individuals can trace most of their ancestry to a small population that migrated out of Africa approximately 50,000 years ago. However, fossil evidence suggests that there were also earlier migrations that failed to establish long-term populations, which raises the question of what made this later migration successful.

Emily Hallett, Eleanor Scerri and colleagues collated evidence from archaeological sites across Africa dated to between 120,000 and 14,000 years ago. They used species distribution modelling to reconstruct the habitat suitability for humans, as determined by variables including leaf area index, annual temperature range and precipitation level. The authors found that the human niche began to expand from 70,000 years ago, most notably in West, Central and North Africa, and was driven by an increase in humans using more diverse habitat types, such as forests and arid deserts. The authors suggest that this increased adaptability could have enabled ancient humans to tackle the range of conditions they were met with on leaving Africa, providing an explanation for the long-term success of the migration 50,000 years ago.