Why Homo Sapiens Failed To Leave Africa Until 60,000 Years Ago

Out of their 300,000 years of existence, Homo sapiens have spend the majority of their time in Africa, the undisputable motherland of our species. It wasn’t until 60,000 years ago that major waves of modern humans ventured out of the home continent to spread across Eurasia and beyond. Small droves of people left in earlier periods, but their lack of genetic legacy among living people suggests their migrations ultimately fell flat. So, what was the big holdup? And what was the big game-changer around this time?

In a new study, scientists from the Max Planck Institute of Geoanthropology, London's Natural History Museum, and the University of Cambridge have illuminated this pivotal chapter in human prehistory using archaeological evidence gathered across Africa, dated to between 120,000 and 14,000 years ago. 

By combining this with historical data on vegetation, rainfall, and temperature fluctuations, the team was able to see the ecological backdrop that shaped our ancestors’ journey around the continent.

Their research found that a clear shift occurred 70,000 years ago. Around this time, Homo sapiens started pushing into new and diverse environments like never before. Dense forests, once unfamiliar terrain, became their home. Even arid deserts were no longer off-limits. Cold and hot regions that were previously inhospitable were conquered and inhabited. 

Perhaps, the researchers wonder, this expansion of ecological niches helped to prepare humans for the risky migrations that successfully led them out of Africa in significant numbers and allowed them to populate the rest of the world.

“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,” Dr Michela Leonardi, lead study author from London’s Natural History Museum, said in a statement.

This suggests that humans were largely limited to Africa for over 200,000 years of prehistory because they hadn’t yet learned how to navigate and thrive in ecologically challenging environments.

"Unlike previous humans dispersing out of Africa, those human groups moving into Eurasia after ~60,000 to 50,000 years ago were equipped with a distinctive ecological flexibility as a result of coping with climatically challenging habitats. This likely provided a key mechanism for the adaptive success of our species beyond their African homeland,” explained Professor Eleanor Scerri from the Max Planck Institute of Geoanthropology.

The question is: What changed around 70,000 years ago? Weirdly, this ability to cope with extreme changes doesn’t appear to coincide with any significant technological development. Equally puzzling, conditions were surprisingly unfavorable when they did eventually make the big push out of Africa around 60,000 years ago. 

“Previous dispersals seem to have happened during particularly favourable windows of increased rainfall in the Saharo-Arabian desert belt, thus creating ‘green corridors’ for people to move into Eurasia. However, 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 sizeable and ultimately successful,” explained Professor Andrea Manica of the University of Cambridge.

The researchers speculate that the most likely explanation is that humans were benefiting from something of a cultural Renaissance, marked by greater contact and the exchange of ideas. It’s a good reminder that Homo sapiens are intensely social creatures. Our brains are brilliant, but it’s the ability to share ideas, communicate, and collaborate that truly sets our species apart.

The new study is published in the journal Nature.