The history of the human family is not as straightforward as you might think. While there’s just one species of human alive today, that was not the case at various points in the past. Studying the genetic markers floating around the Homo sapiens DNA pool can shed light on where our ancestors made contact with other human subspecies. In a new analysis of populations from West Africa, scientists believe they’ve discovered evidence of an as-yet-unidentified “ghost population” of genetically distinct humans.
Throughout most of human history, there have been multiple members of the genus Homo sharing the Earth. That is, until our ancestors swept across the globe, claiming the planet for Homo sapiens. Along the way, the ancestors of modern humans interbred with other human populations. For example, most people from outside Africa have between 1 and 4 percent Neanderthal DNA. Indigenous Australians and a few other populations often carry DNA from Denisovan hominids.
Both Neanderthals and Denisovans left traces of their existence in the form of settlements, art, and fossil remains. However, the hypothesized “ghost population” of hominids in Africa left behind only DNA. Arun Durvasula and Sriram Sankararaman from the University of California obtained genomes from 405 people in four different regions of West Africa.
By analyzing genetic markers, the researchers hoped to determine how much interbreeding happened among the participants’ ancestors. The pair compared genes in their samples to modern human, Neanderthal, and Denisovan genomes. The results were surprising: between 2 and 19 percent of the genes come from an unknown group of archaic humans.
No one has discovered remains or artifacts from this mysterious group of hominids, but we know they existed. The ghost hominids most likely separated from the common ancestor of modern humans and Neanderthals between 360,000 and 1 million years ago. We would need a much larger sample to nail down the exact timeline, but Durvasula and Sankararaman estimate the ancestors of modern Africans interbred with the mystery humans at some point in the past 124,000 years. The researchers also note that it’s possible humans interbred with several waves of different hominids over thousands of years.
Researchers around the world are hoping to learn more about these ancient humans. Once we know more about when and where Homo sapiens encountered these beings, we will know where to look for physical evidence.
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