Researchers have unearthed information of an extinct human species that lived in Africa approximately half a million years ago. Those humans’ genetic material has been transmitted in today’s people.
Evidence of the ‘ghost population’ appeared when scientists studied genomes from west African populations and discovered that about a fifth of their DNA seemed to have originated from the missing group.
Ancient Population’s Genes Found in Modern Humans
Geneticists think that the ancestors of today’s west Africans hybridized with the still-not-discovered archaic humans, numerous thousands of years ago, similar to how ancient Europeans once bred with the Neanderthals.
“In the west Africans we looked at, all have ancestry from this unknown archaic population,” said Sriram Sankararaman, a computational biologist who conducted the study at the University of California in Los Angeles.
Dissimilar to the modern times, the world then was home to cognate species of human. When they found each other, mating was only a natural process. Therefore, modern Europeans have a handful of Neanderthal genes, while indigenous Australians, Polynesians, and Melanesians carry genomes from Denisovans, another species of ancient humans.
Arun Durvasula and Sankararaman have gathered 405 genomes from four west African groups and used statistical methods to learn whether an influx of genes from hybridizing was probable to have taken place in the far past. The research showcased that it had in each of those cases.
By comparing the genomes from African populations that looked different than modern human DNA with genes from Neanderthals and Denisovans, the researchers have determined that the DNA belonged to an unknown group of ancient humans.
“They seem to have made a pretty substantial impact on the genomes of the present-day individuals we studied,” Sankararaman said. “They account for 2% to 19% of their genetic ancestry.”
The four groups analyzed came from three countries: two from Nigeria, one from Sierra Leone, and one from Gambia.
More Research is Needed
The discoveries are not at all definitive, but as per the experts’ best guesses, the ‘ghost population’ separated from the ancestors of Neanderthals and today’s humans between 360,000 and one million years ago. The species of about 20,000 individuals eventually crossbred with the ancestors of modern west Africans in the last 124,000 years.
“It’s very likely that the true picture is much more complicated,” Sankararaman said.
The scientists are now excited to dive into the ancient genes and work out what they do. One prospect is that west Africans kept the DNA because it helped them survive and hybridize.
“It is always interesting and useful to see researchers applying new methods to try to get a better idea of what ancient populations might have been like,” said John Hawks, an anthropologist at the University of Wisconsin-Madison, who was not involved in the research.
“It’s an exciting moment because these studies open a window showing us that there is much more than we thought to learn about our ancestors. But actually knowing who those ancestors were, how they interacted, and where they existed is going to take fieldwork to find their fossil and archaeological remains.
“We do not know what this African population may have been. It is tempting to speculate. But I’ve got to say it is just too soon to know. We haven’t discovered enough fossils in most of Africa to say we know what was there.”
The paper has been published in the journal Science Advances.