(CNN) - We have a lot to learn about our ancient ancestors.
Scientists say they have found evidence of a new population of humans that lived about half a million years ago.
University of California - Los Angeles researchers compared the genetic make-up of more than 400 West Africans with the genetic make-up of Neanderthal and Denisovan genomes. Both are extinct species of early humans.
They ruled out DNA from modern humans and found the presence of DNA from "an archaic ghost population."
According to their research, the “ghost population” of ancestors may have mated with ancestors of people living in what is today West Africa, and that would explain the genetic diversity within modern West African populations.
The findings were published in Wednesday’s issue of the journal Science Advances.