Before the 'Out of Africa' migration that led our ancestors into Eurasia and beyond, human populations learned to adapt to new and challenging habitats including African forests and deserts, which was key to the long-term success of our species' dispersal.
It's incredibly exciting that we were able to look back in time and pinpoint the changes that enabled our ancestors to successfully migrate out of Africa.
Andrea Manica
Today, all non-Africans are known to have descended from a small group of people that ventured into Eurasia around 50,000 years ago. However, fossil evidence shows that there were numerous failed dispersals before this time that left no detectable traces in living people.
In a new study published today in the journal in Nature, scientists say that from around 70,000 years ago, early humans began to exploit different habitat types in Africa in ways not seen before.
At this time, our ancestors started to live in the equatorial forests of West and Central Africa, and in the Sahara and Sahel desert regions of North Africa, where they encountered a range of new environmental conditions.
As they adapted to life in these diverse habitats, early humans gained the flexibility to tackle the range of novel environmental conditions they would encounter during their expansion out of Africa.
This increase in the human niche may have been the result of social adaptations, such as long-distance social networks, which allowed for an increase in cultural exchange. 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.
Andrea Manica, Professor of Evolutionary Ecology in the University of Cambridge's Department of Zoology, who co-led the study with Professor Eleanor Scerri from the Max Plank Institute of Bioanthropology in Germany, said: "Around 70,000-50,000 years ago, the easiest route out of Africa would have been more challenging than during previous periods, and yet this expansion was big - and ultimately successful."
Manica added: "It's incredibly exciting that we were able to look back in time and pinpoint the changes that enabled our ancestors to successfully migrate out of Africa."
Dr Emily Hallett of Loyola University Chicago, co-lead author of the study, said: "We assembled a dataset of archaeological sites and environmental information covering the last 120,000 years in Africa. We used methods developed in ecology to understand changes in human environmental niches - the habitats humans can use and thrive in - during this time."
Dr Michela Leonardi at the University of Cambridge and London's Natural History Museum, the study's other lead author, said: "Our 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."
Many explanations for the uniquely successful dispersal out of Africa have previously been made, from technological innovations, to immunities granted by interbreeding with Eurasian hominins. But there is no evidence of technological innovation, and previous interbreeding does not appear to have helped the long-term success of previous attempts to spread out of Africa.
"Unlike previous humans dispersing out of Africa, those human groups moving into Eurasia after around 60-50,000 years ago were equipped with a distinctive ecological flexibility as a result of coping with climatically challenging habitats," said Scerri. "This likely provided a key mechanism for the adaptive success of our species beyond their African homeland."
Previous human dispersals out of Africa - which were not successful in the long term - 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.
The environmental flexibility developed 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.
This research was supported by funding from the Max Planck Society, European Research Council and Leverhulme Trust.
Adapted from a press release by the Max Planck Institute of Geoanthropology, Germany
Reference: Hallett, E. Y. et al: 'Major expansion in the human niche preceded out of Africa dispersal.' Nature, June 2025. DOI: 10.1038/s41586-025-09154-0.
