Four groups of early human ancestors have been identified from the most complete Neanderthal genome ever produced according to a report by an international team of anthropologists led by Svante Pääbo from the University of California at Berkeley published in the Dec. 18, 2013, edition of the journal Nature
Humans from Africa, Neanderthals, Denisovans, and an unknown human ancestor that is probably a Homo erectus all contributed to the modern human genome according to comparison of modern man with this new and most detailed Neanderthal gene sequencing ever accomplished.
The DNA analysis of Neanderthals and Denisovans indicates these groups had a high instance of inbreeding. Both Neanderthals and Denisovans existed in isolated groups that did not travel extensively so mate selection was found to be quite often from the same family or a closely related member of the group. The inbreeding may have contributed to the demise of these peoples.
Denisovan DNA is only found in Australian aborigines, New Guineans, some Pacific Islanders, the Han Chinese, other mainland Asian populations, and Native Americans. The most recent Denisovan DNA analysis suggests that these peoples mated with Homo erectus that came from Eurasia.
About two percent of the DNA of non-African people living today is Neanderthal DNA and between six and 0.2 percent of modern non-African people’s DNA is Denisovan DNA.
The researchers have found evidence that at least four species of human ancestor interbred to produce modern man. The frequency of interbreeding cannot be determined from DNA analysis.