Plagnol said different parts of the genome have different ancestry, so an individual could have a fraction of a certain chromosome that was inherited from a Neanderthal, but then possess "very typical homo sapiens mtDNA."
The scientists are not certain what early human group could have contributed to West African DNA, but both Europeans and Africans in the study showed about the same 5 percent archaic contribution. Neanderthals are believed to have originated in Africa around 400,000 years ago, but they left and then settled in Europe, hence the apparent lack of interaction with modern humans in Africa.
Alan Templeton, of Washington University in St.Louis, also conducted DNA studies and came to similar conclusions.
"The humans who were in Africa and the humans who were in Eurasia were regularly interchanging genes," he said, "there was interbreeding and when humans came out of Africa 100,000 years ago they did not replace these other human populations in Eurasia."
New technologies are being developed to sequence nuclear DNA from fossils, so in the near future, scientists may learn more about how modern human genes compare with those of archaic humans, like Neanderthals.
