(CNN) – A mysterious population of ancient humans lived in West Africa about half a million years ago, and scientists believe their genes still live in people today.
This “population of archaic ghosts” seems to have separated from modern humans before Neanderthals separated from the family tree, according to research published by the magazine Science Advances
The separation seems to have taken place between 360,000 and one million years ago, say researchers at the University of California, Los Angeles (UCLA). These ancient humans had babies with the ancestors of today’s Africans, just as Neanderthals reproduced with the ancestors of modern Europeans, wrote geneticists Arun Durvasula and Sriram Sankararaman. The DNA of this archaic population represents between 2% and 19% of the genetic ancestry of modern West Africans, they said.
Well-established research, according to the study, has determined the existence of Neanderthal DNA in modern European populations and Denisovan DNA in oceanic populations.
The UCLA researchers said that “although several studies have revealed contributions from deep lineages to the ancestry of current Africans, the nature of these contributions remains poorly understood.” This is partly due to the scarce fossil records in Africa and the difficulty of obtaining ancient DNA.
UCLA scientists overcame these challenges to find the “ghost” of the Hominini tribe by using computer modeling techniques in modern DNA.
READ: They discover remains of those who were the last of the first humans to walk upright
They built “genetic maps of archaic descent” in four ethnic populations of West Africa living in three countries: Nigeria, Sierra Leone and Gambia.
The researchers compared 405 genomes of West Africans with Neanderthal and Denisovan genomes, and looked for whether there had been crossings between an unknown hominid whose ancestors separated from the human family tree before the Neanderthals. The data suggests that this may have involved multiple populations.
Professor Joel D. Irish, a bioarchaeologist at John Moores University in Liverpool, told CNN that there were probably many different ancient human populations.
“I think at one time, there would have been all kinds of populations, with a genetics different enough to look a little different,” he said.
“Everyone tends to mate with everyone. I think we’re going to find more and more of these poblaciones ghost ’populations along the way.”
After extracting the first genomes from the bones of the Stone Age hominids, scientists discovered in 2010 that the first ancestors of Europeans, Asians and Americans reproduced with Neanderthals.
Last month, researchers at the Princeton Lewis-Sigler Institute of Integrative Genomics said they also detected Neanderthal ancestry in Africans for the first time.
READ: Neanderthal genes could explain the shape of our skulls, says a study (2018)
Their data indicated that a wave of modern humans left Africa for Europe about 200,000 years ago and crossed with Neanderthals, before emigrating back to Africa.
That cast doubt on the widely spread theory of human migration “outside of Africa,” which means that modern humans originated in Africa and dispersed to the rest of the world in a single wave between 60,000 and 80,000 years ago.
CNN’s Katie Hunt contributed to this story.