Our complex past with the Denisovans saw us interbreed twice

  Last updated March 16, 2018 at 10:03 am

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Scientists are adding more pieces to the puzzle of our two hominid cousins.


The Denisova cave in the Altai mountains in Siberia where bone fragments of the Denisovan hominid were found. Our relationship with the Denisovans is more complex than we previously thought.


Just weeks after we learned of the artistic ability of the Neanderthals, a new study suggests a more diverse genetic history than previously thought between the Denisovans and modern humans. In fact, we interbred not once but twice.


When Denisovans were first revealed – as recently as 2010 – as a species quite distinct from Neanderthals (thanks to an important discovery by paleoanthropologists in a cave in southern Siberia), it was also found that there was a genetic overlap with humans from Oceania. The genomes of modern Papuans are 5 per cent Denisovan.


Denisovan ancestry was also found in parts of East Asia, and it was assumed that this was a result of migration.


However, new research from the University of Washington’s School of Public Health shows that there are two quite distinct populations, suggesting two quite distinct episodes of genetic admixing, or intermixing.


“In this new work with East Asians we find a second set of Denisovan ancestry that we do not find in the South Asians and Papuans,” said senior author Sharon Browning, a research professor of biostatistics. “This Denisovan ancestry in East Asians seems to be something they acquired themselves.”


A new genome-analysis method


In fact, after studying more than 5,600 whole-genome sequences from individuals from Europe, Asia, America and Oceania, Browning and colleagues determined that the Denisovan genome is actually more closely related to the modern East Asian population than to modern Papuans.


“When we compared pieces of DNA from the Papuans against the Denisovan genome, many sequences were similar enough to declare a match, but some of the DNA sequences in the East Asians, notably Han Chinese, Chinese Dai, and Japanese, were a much closer match with the Denisovan.”


The discovery was made while the research team was developing a new genome-analysis method for comparing whole genomes between modern human and Denisovan populations, making use of genomic information from the UK10K project, the 1,000 Genomes Project, and the Simons Genome Diversity Project.


Browning says it is assumed the admixing occurred fairly quickly after humans moved out of Africa around 50,000 years ago, but it is not known where. She theorises that the ancestors of Oceanians admixed with a southern group of Denisovans while the ancestors of East Asians admixed with a northern group.


The next stage of the research will expand the reach to other parts of Asia and the world, including Native Americans and Africans.


“We want to look throughout the world to see if we can find evidence of interbreeding with other archaic humans. There are signs that intermixing with archaic humans was occurring in Africa, but given the warmer climate no one has yet found African archaic human fossils with sufficient DNA for sequencing.”


The paper published in Cell.


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About the Author

Nick Carne
Nick Carne is the Editorial Manager for the Royal Institution of Australia.