It is thought that between 300,000 to 400,000 years ago, an ancestral group of H. heidelbergensis left Africa and then split shortly after. One branch ventured northwestward into Western Asia and Europe and became the Neanderthals. The other branch moved east, becoming Denisovans.

Discoveries at a cave in southern Siberia called Denisova, after an 18th-century hermit occupant, led scientists to examine forensic evidence of early habitation by both Neanderthals and H. sapiens, and a few small bones of a species that was new.

The cold temperatures in the caves preserved genetic material, which allowed an analysis of the DNA taken from the pinky bone of a girl found at Denisova. This child, who lived about 40,000 years ago, was possibly from an unknown species of human. More surprisingly, her DNA matched about 4% to 6% of the DNA of the modern humans indigenous to Australia, Melanesia, and other areas of the western Pacific.

This distribution suggests that these “Denisovans” had journeyed as far away as Southeast Asia, where they must have interbred with modern humans. A newer study confirms this, and it suggests that there were distinct populations of Denisovans, rather than a single population. New genome-analysis was able to compare the Denisovan genome to that of 5,600 Europeans, Asians, Americans and Oceanians and found that Denisovans were more closely related to modern East Asians, specifically Han Chinese, Chinese Dai and Japanese.