The earliest modern humans are thought to have emerged in Africa some 300,000 years ago. However, the fossil record reveals that there were numerous attempts and false starts. For example, 180,000-year-old Homo sapien bones have been found in Israel. It was not until some 50,000 years ago that a band of humans made the crossing into Eurasia and established a permanent presence, eventually settling in areas as diverse as the mountains of Nepal and the rainforests of Malaysia. It is from this intrepid troupe of prehistoric explorers that all non-Africans descend from.
But why did this particular group succeed when all others before them had failed? Researchers writing in Nature attribute their triumph to tens of thousands of years of learning how to live in and exploit different habitats within Africa.
“Unlike previous humans dispersing out of Africa, those human groups moving into Eurasia after approximately [60,000 years] to [50,000] years ago were equipped with a distinctive ecological flexibility as a result of coping with climatically challenging habitats,” Eleanor Scerri, an archaeologist at the Max Planck Institute of Geoanthropology in Germany, said in a press release. “This likely provided a key mechanism for the adaptive success of our species beyond their African homeland.”
Read More: Early Humans Thrived in Africa's Tropical Rainforests 150,000 Years Ago
Successful Human Migration
The fact that the migration was successful when others were not is particularly puzzling because previous attempts at dispersal occurred during periods of increased rainfall, when a ‘green corridor’ would have offered a more hospitable route through the Saharo-Arabian desert belt.
“However, around [70,000 years to 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,” Andrea Manica, an evolutionary ecologist at the University of Cambridge, said in a press release.
There have been many theories put forward to explain why. Some point to a leap in cognition and the ability to communicate symbolically; others to the development of new weapons, specifically projectile weapons. Another theory is that mating with hominins already living in Eurasia provided Homo sapiens with certain genetic protection and immunities – but, the researchers argue, this hadn’t helped previous human populations who had also attempted to disperse and had similarly intermingled with other hominin species.
Learning to Thrive in Different Habitats
Instead, the team looked at populations within Africa over the past 120,000 years, investigating which bioclimatic niches humans inhabited over the millennia. Using techniques commonly employed in the field of ecology to model the distribution of species, the team analyzed how human niches expanded and contracted over time.
“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,” Michela Leonardi of London’s Natural History Museum said in a press release.
This expansion peaked around 50,000 years ago, coinciding with the migration out of Africa. Humans were then living in the forests of West Africa and the semi-arid Sahelian regions of North Africa – regions that were previously very rarely populated. While it cannot be said with certainty why this expansion occurred, the study’s authors suggest it could be that climatic instability encouraged humans to broaden their niche. Whatever the reason, the researchers argue that it gave them a level of flexibility that prepared them for a life in Asia and Europe.
“We show that successful expansion into Eurasia and the long-term establishment of populations there were part of a process that fundamentally started within Africa,” the researchers wrote. “Essentially, we document the inception of an unquestionably African process originating 70 ka that has resulted in today’s unparalleled human ecological plasticity.”
Read More: Humans Arose From Two Ancestral Populations That United 300,000 Years Ago
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Nature. Major expansion in the human niche preceded out of Africa dispersal
Natural History Museum. Humans left Africa 40,000 years earlier than we thought
Rosie McCall is a freelance writer living in London. She has covered science and health topics for publications, including IFLScience, Newsweek, and Health.
