About 50,000 years ago, ancient humans in what is now West Africa apparently procreated with another group of ancient humans that scientists didn’t know existed.
There aren’t any bones or ancient DNA to prove it, but researchers say the evidence is in the genes of modern West Africans. They analyzed genetic material from hundreds of people from Nigeria and Sierra Leone and found signals of what they call “ghost” DNA from an unknown ancestor.
The findings on ghost DNA, published in the journal Science Advances, further complicate the picture of how Homo sapiens — or modern humans — evolved away from other human relatives. “It’s almost certainly the case that the story is incredibly complex and complicated and we have kind of these initial hints about the complexity,” says Sriram Sankararaman, a computational biologist at UCLA.
The unusual DNA found in West Africa isn’t associated with either Neanderthals or Denisovans. Sankararaman and his study co-author, Arun Durvasula, think it comes from a yet-to-be-discovered group.
“We don’t have a clear identity for this archaic group,” Sankararaman says. “That’s why we use the term ‘ghost.’ It doesn’t seem to be particularly closely related to the groups from which we have genome sequences from.”