Final answer:
Humans interbred with Neanderthals after migrating out of Africa. Evidence includes the presence of up to 4 percent Neanderthal DNA in modern European populations and the first-generation hybrid individual, Denisova 11. Early humans also interbred with Denisovans, sharing ancestors with Neanderthals, and evidence suggests multiple interbreeding events between these species.
Step-by-step explanation:
From mitochondrial DNA and nuclear DNA studies, we have learned that early humans interbred with Neanderthals. This interbreeding occurred after early humans emerged from Africa and spread out to populate different parts of the globe. The discovery of bones from a first-generation hybrid individual known as Denisova 11, who had a Denisovan father and Neanderthal mother, provides strong evidence of the interbreeding between these distinct Homo species during the Mid-Pleistocene.
Moreover, DNA evidence has revealed that modern European and Middle Eastern populations possess between 1 and 4 percent Neanderthal DNA. Additional studies have indicated that modern humans have also inherited Denisovan DNA, particularly in regions like Tibet, Melanesia, and Indigenous Australia, though these figures are subject to ongoing research and debate. This genetic mingling suggests a common occurrence of mating among Homo sapiens, Neanderthals, and Denisovans when these groups encountered each other.
Fossil remains from Europe and Africa and genetic analyses have further indicated that other early human species, such as Homo heidelbergensis, may have been direct ancestors to Neanderthals, Denisovans, and possibly modern humans. It's worth noting that Neanderthals and Denisovans were more closely related to each other than to modern humans, and the interbreeding events replaced some Denisovan DNA with that of Neanderthals and early humans.a