Siberia harboured Denisovan DNA (Image: J. Krause)

THE Denisovans, mysterious cousins of the Neanderthals, occupied a vast realm stretching from the chill expanse of Siberia to the steamy tropical forests of Indonesia – suggesting the third human of the Pleistocene displayed a level of adaptability previously thought to be unique to modern humans.

Our first tantalising glimpse of the Denisovans came last year with DNA analysis of a bone and tooth found in a Siberian cave. The DNA was distinct enough from Neanderthals’ to suggest tens of thousands of years of independent evolution.

Before they disappeared, the Denisovans found time to interbreed with Homo sapiens. As a result, 5 per cent of the Denisovan genome lives on – not in the inhabitants of Siberia but in Papua New Guineans, living thousands of kilometres to the south-east (Nature, DOI: 10.1038/nature09710).


“I don’t think many people would have predicted that,” says Mark Stoneking of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Stoneking has now compared the Denisovan genome with an additional 33 populations from mainland Asia, Indonesia, the Philippines, Polynesia, Australia and Papua New Guinea. He found Denisovan genes in east Indonesia, Australia, Papua New Guinea, Fiji and Polynesia (American Journal of Human Genetics, DOI: 10.1016/j.ajhg.2011.09.005).

That suggests that the Denisovan genes in Papua New Guinea were by no means a freak result. Instead, Stoneking thinks the Denisovans lived in south-east Asia, and that the interbreeding with modern humans happened there. If confirmed, the Denisovans’ range is particularly startling because it runs north to south (see map). Genetic evidence suggests that it is harder to migrate north-south than east-west, because climate and ecology change over shorter distances (American Journal of Physical Anthropology, DOI: 10.1002/ajpa.21533).

“The Denisovans were spread across an extraordinarily wide [north-south] geographic and ecological zone,” says Stoneking, “wider than any hominin other than modern humans – wider than Neanderthals.”

The fact that Neanderthals inhabited a much narrower north-south zone “does seem to imply that there was something different about Denisovans’ behavioural capabilities that allowed them to exploit a wider range of environments”, Stoneking says.

“There was a difference in Denisovan behaviour that let them exploit a wider range of environments”

We must be careful about using genetics to infer where people lived, warns John Stewart of Bournemouth University in the UK. It may be that the Denisovans interbred with modern humans somewhere in central Asia, and that a later migration carried their genes south-east.

Fossil remains of south-east-Asian Denisovans would help to examine that possibility. “There are a lot of enigmatic fossils in central Asia, China and south-east Asia,” says David Reich of Harvard Medical School in Boston.

“It seems likely that some of them are Denisovan.”

Across Asia in two waves Read more: Click here to read a longer version of this section The genes of Denisovans in modern humans are helping to reveal how our species colonised Asia, Australia and the Pacific islands. Mark Stoneking of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, found Denisovan DNA in modern humans living in east Indonesia, Polynesia, Australia and Papua New Guinea. People from mainland Asia and west Indonesia didn’t have any though, suggesting they are descendants of a second wave of modern humans across Asia – this time without Denisovan interbreeding. He suspects modern humans settled in the Middle East and migrated eastwards twice. Independent support comes from Eske Willerslev of the Natural History Museum of Denmark in Copenhagen. His team sequenced the genome of an Indigenous Australian and compared it with Han Chinese, European and African genomes. They calculated that the Indigenous Australians split from the others between 75,000 and 62,000 years ago. The Chinese and European populations split between 38,000 and 25,000 years ago (Science, DOI: 10.1126/science.1211177). That, again, suggests two migrations across Asia.