Model of the geographic distribution of species in the genus Homo over the last 2 million years.The horizontal axis represents geographic location; the vertical axis represents time in millions of years ago.
French, Han Chinese, and Papua New Guinean) than with Sub-Saharan African populations (e.g. They also found that the Neanderthal component in non-African modern humans was more related to the Mezmaiskaya Neanderthal (Caucasus) than to the Altai Neanderthal (Siberia) or the Vindija Neanderthals (Croatia).
Although less parsimonious than recent gene flow, the observation may have been due to ancient population sub-structure in Africa, causing incomplete genetic homogenization within modern humans when Neanderthals diverged while early ancestors of Eurasians were still more closely related to Neanderthals than those of Africans to Neanderthals.
On the basis of allele frequency spectrum, it was shown that the recent admixture model had the best fit to the results while the ancient population sub-structure model had no fit–demonstrating that the best model was a recent admixture event that was preceded by a bottleneck event among modern humans—thus confirming recent admixture as the most parsimonious and plausible explanation for the observed excess of genetic similarities between modern non-African humans and Neanderthals.
There have been arguments in favor of archaic human admixture with modern humans through interbreeding of modern humans with Neanderthals, Denisovans, and/or possibly other archaic humans over the course of human history.
Neanderthal-derived DNA accounts for an estimated 1–4% of the Eurasian genome, but it is significantly absent or uncommon in the genome of most Sub-Saharan African people.
In Oceanian and Southeast Asian populations, there is a relative increase of Denisovan-derived DNA.
An estimated 4–6% of the Melanesian genome is derived from Denisovans.
Recent noncomparative DNA analyses—as no specimens have been discovered—suggest that African populations have a genetic contribution from a now-extinct archaic African hominin population.
Nevertheless, there still are some doubts about the recent admixture events among a number of researchers.
Ancient subpopulation structure ancestral to modern humans, Neanderthals, Denisovans, and other possible archaic humans has been proposed as an alternative explanation for the observed genetic similarities.
Through whole-genome sequencing, a 2010 draft sequence of the Neanderthal genome revealed that Neanderthals shared more alleles with Eurasian populations (e.g.