A paper published in Nature (Hallett, E.Y., Leonardi, M., Cerasoni, J.N. et al. Major expansion in the human niche preceded out of Africa dispersal. Nature 644, 115–121 (2025). https://doi.org/10.1038/s41586-025-09154-0) on June 18, 2025, explains why the final Out Of Africa event, 50,000 years ago, was the successful one.
The premise of the paper is that human beings in Africa adapted to living in different environments within the continent (deserts, savannas, grasslands, and jungles) expanding their niche. They could face the weather, and survive in different habitats. It was this flexibility, not tools or special genes that allowed them to expand and move out of Africa. In the authors words:
"The expansion of the human niche beginning around 70 ka in Africa is driven by a gradual increase in human preference for forest and desert biomes, allowing them to expand into regions that were previously rarely populated: (1) forests of West Africa, (2) forests of Central Africa and, eventually, (3) arid Saharan regions and semi-arid Sahelian regions of North Africa. This increased ability to adapt to new habitats, ranging from the extremes of equatorial forests to arid deserts, would have allowed these populations of humans the ecological flexibility to tackle a range of new environmental conditions encountered during the expansion out of Africa, allowing them to succeed where earlier migrations out of Africa had previously faltered. The expansion of the human niche in Africa starting around 70 ka, therefore, offers an explanation for the successful worldwide expansion of human populations about 50 ka"
The previous Out of Africa migrants that survived
I disagree with this point of view.
It is clear that a first wave of Homo sapiens didn't survive. They left Africa 100 ky ago.
But, we have the Denisovan and Neanderthals thriving for hundreds of thousands of years in freezing Eurasia, from Tibet to Spain. In a climate that never existed in Africa (glacial ice and extremely low temperatures). Yet, they were extremely well adapted to their niche, with tools, social structures, and flexibility to hunt and survive.
They had been preceded by the Homo erectus, and probably Homo habilis by at least 1 million years in their migration into Eurasia. And H. erectus lived there, and prospered for hundreds of thousands of years adapting to tropical climes in Indonesia and freezing winters in Northern China.
Luck and Chance
Perhaps the demise of these other groups was not dictated by modern human "flexibility" adapting to African ecological niches, which gave them tools to survive. We were lucky. It was just chance and good fortune that allowed small groups of hominins to survive the deadly environment (drought, wild beasts, volcanic eruptions, disease, infections, lack of food, etc.)
Human Beings almost became extinct 900 ky ago
See these articles published in Sept. 2023: "Did our ancestors nearly die out?" (Nick Ashton, Chris Stringer, Science 381,947-948 023).DOI:10.1126/science.adj9484) commenting "Genomic inference of a severe human bottleneck during the Early to Middle Pleistocene transition" (Wangjie Hu et al., Science 381, 979-984 (2023).DOI:10.1126/science.abq7487). Hu et al point out that:
"Results showed that human ancestors went through a severe population bottleneck with about 1280 breeding individuals between around 930,000 and 813,000 years ago. The bottleneck lasted for about 117,000 years and brought human ancestors close to extinction"
Our ancestors were reduced from almost 100,000 individuals to a mere 1,280 individuals some 900,000 years ago, and this went on for 117,000 years. It was touch and go. This dreop in population was caused by climate change with glaciations becoming long-term events, cooling the oceans and provoking drought which in turn affected the animals in Africa, Europe and Asia.
Then, population recovered and a speciation event took place, and the ancestor of modern humans, Neanderthals and Denisovans appared, around 750 to 550 ky ago.
Ashton and Stringer add that " Europe was probably completely depopulated after a previously unrecognized cold phase about 1,100,000 years ago" (https://www.science.org/doi/10.1126/science.adf4445) this event eliminated the first hominins to people Europe 1.5 Ma, the the Sima del Elefante people, perhaps descended from the Dmanisi hominins from Georgia (1.8 MA). "these extreme conditions led to the depopulation of Europe, perhaps lasting for several successive glacial-interglacial cycles." It was only later (1 Ma - 900 ky) that Europe was repopulated "by Homo antecessor, which may have been a more resilient species with evolutionary or behavioral changes that allowed survival under the increasing intensity of glacial conditions."
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2025 by Austin Whittall ©
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