Ancient DNA reveals tryst between extinct human species


New analysis of a bone fragment from a Siberian cave has suggested that two very distinct groups of humans did in fact interbreed - and a few times.

The Neanderthals and Denisovans were "sister groups" and our closest extinct human relatives.

What we know about Neanderthals is plenty: They were short, stocky, had large noses (for European winters in the Ice Age), and larger bodies than modern humans. Neanderthals also lived in the cave. The study was published Wednesday in the journal Nature. She was born into a tribe of Neanderthals, a sub-human species or a "hominin" that existed until 40,000 years ago. Now, a research team led by scientists at the Max Planck Institute for Evolutionary Anthropology has sequenced the genome of Denisova 11, a 50,000-year-old individual from Denisova Cave in Siberia, and discovered that she had a Neanderthal mother and a Denisovan father.

Denisovans - now extinct - were an early ancestor of humans first identified from DNA analysis of a finger bone found in the same place 10 years ago.

The bone is thick, which means that it belonged to someone at least 13 years old.

The researchers called that individual Denisova 11, and they began searching the bone for nuclear DNA. Neanderthal fossils have been found within the same cave despite this, the results indicate that the child's mother did not come from the earlier eastern population but was more closely related to Neanderthals found much further west consistent with the genetics of other later Neanderthals from the East.

This handout picture taken on June 14, 2015 and obtained from the University of Oxford/Max Planck Institute on August 22, 2018 shows a bone fragment of "Denisova 11", evidence of interbreeding of a Neanderthal and a Denisovan, found in 2012 by Russian archaeologists at Denisova Cave in the Altai Mountains of Siberia.

Interbreeding between the two groups is known to have occurred from past studies - as well as with our own species, which left a trace in the DNA of today's people - but the new study is the first to identify a first-generation child with Neanderthal and Denisovan parents. "Neandertals and Denisovans may not have had many opportunities to meet".

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"They managed to catch it in the act - it's an wonderful discovery", said Sharon Browning, a statistical geneticist at the University of Washington who was not involved in the new study.

"The Denisova 11 individual is only represented by a single small bone fragment", said co-author Dr. Bence Viola, from the Department of Anthropology at the University of Toronto.

Until more fossil evidence is uncovered, the enigmatic Denisovans will continue to remain something of a mystery.

Till a few years ago, we used to think that homo sapiens wiped out other hominins by killing them due to overwhelming numbers.

This suggests that Neanderthals were migrating back and forth across Eurasia tens of thousands of years before they disappeared.

It turned out later that two teeth, one discovered in 1984 and the other in 2000 in the same cave, were also Denisovan.

One of the future implications of this study is that we now have more support than ever to hunt for Denisovan fossils in Oceania, the region comprising Melanesia, Micronesia, Polynesia and Australasia.

The fossil could instead have come from a population with roughly an equal mix of Neanderthal and Denisovan ancestry, he said.