Human Origins are getting more complex as DNA tells the tale

Instead, the genetic analysis shows, modern humans encountered and bred with at least two groups of ancient humans in relatively recent times: the Neanderthals, who lived in Europe and Asia, dying out roughly 30,000 years ago, and a mysterious group known as the Denisovans, who lived in Asia and most likely vanished around the same time.

Apparently, modern human DNA varies quite a bit across the globe. Humans outside Africa have around 2.5% Neanderthal DNA, and some Asian communities have around 5% Denisovian DNA. Southeastern Asians have both Neanderthal and Denisovian DNA. Modern humans have been the only human species since Homo floresiensis died out about 17,000 years ago. We don’t know how much, if any, H. floresiensis DNA is present in modern humans, because we don’t have any well-preserved DNA for that species.

There is no hard and fast rule about what distinguishes one species from another, but the fact that modern humans apparently interbred with at least two now-extinct human species may have been responsible for some of our disease resistance. The fact that these genes survived and spread from a small number of hybrid offspring indicates the genes increased the hardiness of modern humanity.

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