Before we became the only remaining humans on the planet, Homo sapiens mated with Neanderthals and the closely related Denisovans. New research is now revealing that the common ancestor of Neanderthals and Denisovans interbred with its own predecessor, a population of “superarchaic” hominids.
This new model suggests a rewritten history of human evolution, and, if it holds, demonstrates that early human species interbred a lot more than scientists initially thought.
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The researchers developed a model based on a sample of modern European genome from the Simons Genome Diversity Project, as well as available Neanderthal genomes.
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They followed how mutations in either group would be carried forward or jump across species. According to their statistical analysis, the model that best fit the data was one where Neanderthals interbred with humans, Denisovans mixed with the superarchaic ancestor, and now, the novel hypothesis, that genetic information flowed between the superarchaic population and the Neandersovan ancestor population as well.
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The model comes with several other implications—not only would it push back the date that Neanderthals and Denisovans split, but it also predicts that humanity’s ancestors expanded out of Africa only three times: an early ancestor 1.9 million years ago, “Neandersovans” 700,000 years ago, and modern humans 50,000 years ago.
