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Mapping the DNA inheritance from Neanderthal and Denisovan ancestors

Indigenous Australians may have a dash more Denisovan than Neanderthal in their DNA, with genetic traces of the mysterious population of hominids popping up in surprisingly high doses, according to fresh research.

An archaic ancestry map produced by a Harvard Medical School-UCLA research team also suggests those from countries to Australia's north, including Papua New Guinea, may have more Denisovan ancestry than initially believed.

Little is understood about Denisovans because so few fossil remains have been found - to date just two teeth, a finger and a toe bone. However they lived around the time of Neanderthals and, according to this study published in the journal Current Biology on Monday, interbred with modern humans about 100 generations after modern humans had their trysts with Neanderthals.

According to Harvard Medical School geneticist David Reich, some genetic traits could still be evident today. For example, Denisovan genes could potentially be linked to a more subtle sense of smell in Papua New Guineans or high-altitude adaptation among Tibetans.

"There are certain classes of genes that modern humans inherited from the archaic humans with whom they interbred, which may have helped the modern humans to adapt to the new environments in which they arrived," he said.

The researchers compared known Neanderthal and Denisovan gene sequences across more than 250 genomes from 120 non-African populations.


In people from Oceania, the average size of Denisovan genetic fragments was found to be larger than Neanderthal fragments. The Oceania region includes countries such as Australia, New Zealand, Fiji and Papua New Guinea.

Professor Reich also noted the comparative genomics study revealed that both Denisovan and Neanderthal ancestry has been lost from the X chromosome, as well as genes expressed in the testes. This could explain reduced male fertility, which is associated with interbreeding.


A global map of Neanderthal and Denisovan ancestry in modern humans.

The findings shed new light on how the Denisovans dispersed from south-western Siberia to Southeast Asia.

However UCLA's Sriram Sankararaman, a member of the research team, said the ancestry map did not answer definitively how far the Denisovans travelled. This was because their DNA could have reached South Asia and later Australian shores, albeit diluted, carried by hybrid offspring or descendants of hybrid offspring.

Denisovans are named named after a Russian hermit, Denis, who in the 18th century lived in a cave where Denisovan remains were later discovered. The cave's cool climate helped preserve the DNA.