How did early humans successfully colonise beyond Africa? Their spread in various African climes gave them a unique ‘ecological flexibility’, says research

For years, scientists have pondered the reasons behind humanity’s successful spillover from Africa to Eurasia and beyond. Various hypotheses have been suggested, ranging from interbreeding between different groups of humans to technological innovation. Now, a new study says it was humans’ successful spread within the African continent itself that helped them win the rest of the world.

This happened around 70,000 years ago. Humans spread out into the Sahara and the Sahel, the dry scrublands that separate the world’s largest desert from the green equatorial forests of sub-Saharan Africa. Humanity spread out in the latter climes as well.

A team of scientists assembled a dataset of archaeological sites and environmental information covering the last 120,000 years in Africa. They used methods developed in ecology to understand changes in ‘human environmental niches’ — the habitats humans can use and thrive in — during this time. 

Their results showed that the human niche began to expand significantly from 70,000 years ago, and that this expansion was driven by humans increasing their use of diverse habitat types, from forests to arid deserts, according to a statement by the University of Cambridge.

The study suggests that this increase in the human niche may have been due to increased social interactions between different groups of early humans on the African continent.

“The process would have been self-reinforcing: as people started to inhabit a wider proportion of the African continent, regions previously disconnected would have come into contact, leading to further exchanges and possibly even greater flexibility. The final outcome was that our species became the ultimate generalist, able to tackle a wider range of environments,” the statement noted.

The researchers also added that previous human dispersals out of Africa, that were unsuccessful, seem to have happened during particularly favourable windows of increased rainfall in the Saharo-Arabian desert belt, which created ‘green corridors’ for people to move into Eurasia.

However, the environmental flexibility developed by early humans in Africa from around 70,000 years ago ultimately resulted in modern humans’ unique ability to adapt and thrive in diverse environments, and to cope with varying environmental conditions throughout life.

The paper, titled Major expansion in the human niche preceded out of Africa dispersal, has been published in the journal Nature on June 18, 2025.

The authors of the paper are Emily Y Hallett, Michela Leonardi, Jacopo Niccolò Cerasoni, Manuel Will, Robert Beyer, Mario Krapp, Andrew W Kandel, Andrea Manica and Eleanor M L Scerri.