Cave of Mystery -Evidence of a Lost Branch of Human Evolution

Ancient Human Species


In August 2018, researchers discovered a bone fragment from a girl whose mother was a Neanderthal and father was a Denisovan in a remote cave in Siberia. In the study, researchers estimate that this hybrid child lived between 79,100 and 118,100 years ago. Modern humans, scientists discovered, share a common ancestor with Denisovans and Neanderthals that lived roughly 600,000 years ago. Later — approximately 390,00 years ago — the Neanderthal and Denisovan lineages split.

Over the past decade, reports Carl Zimmer in the New York Times, the Denisova Cave “has yielded some of the most fascinating fossils ever found. To the naked eye, they are not much to look at — a few teeth, bits of bone. But the fossils contain DNA dating back tens of thousands of years. That genetic material shows that Denisovans were a distinct branch of human evolution, a lost lineage. At some point in the distant past, the Denisovans disappeared — but not before interbreeding with modern humans. Today, people in places like East Asia and New Guinea still carry fragments of Denisovan DNA.”


Denisova Cave


The August finding in the cave in an isolated river valley in Siberia was “sensational” said Johannes Krause, who studies ancient DNA at the Max Planck Institute for the Science of Human History in Jena, Germany. “Now we have the love child of two different hominin groups, found where members of both groups have been found. It’s quite a lot of things happening in one cave through time.”

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“Everyone said, ‘These Denisovans, we have no idea how old they are,’” said Katerina Douka, an archaeologist at the Max Planck Institute for the Science of Human History in Germany. Over the past six years, Dr. Douka and other experts have been creating a history of the cave, dating 103 layers of sediment on the cave floor, as well as 50 items found in them, including bones, pieces of charcoal and tools.

The Max Planck scientists unveiled this chronology in a pair of papers published yesterday that shows that humans occupied the cave for perhaps as long as 300,000 years, raising some intriguing hints that Denisovans may have been capable of sophisticated thought, on par with modern humans.

The August research findings suggest that the woman may have been just a teenager when she died more than 50,000 years ago, too young to have left much of a mark on her world. But a piece of one of her bones, unearthed in in the cave in 2012, may make her famous. Enough ancient DNA lingered within the 2-centimeter fragment to reveal her startling ancestry: She was the direct offspring of two different species of ancient humans, Neanderthal and the mysterious Denisovan— extinct groups of hominins that separated from each other more than 390,000 years ago.

An analysis of the woman’s genome, continues Gretchen Vogel in Science, indicates her mother was Neanderthal and her father was Denisovan, the mysterious group of ancient humans discovered in the same Siberian cave in 2011. It is the most direct evidence yet that various ancient humans mated with each other and had offspring.


Denisovan Bone Fragment

This bone fragment harbors the most direct evidence yet of ancient interspecies mating. Thomas Higham, University of Oxford

Based on other ancient genomes, researchers already had concluded that Denisovans, Neanderthals, and modern humans interbred in ice age Europe and Asia. The genes of both archaic human species are present in many people today. Other fossils found in the Siberian cave have shown that all three species lived there at different times.

Viviane Slon, a paleogeneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who did the ancient DNA analysis, says when she saw the results, her first reaction was disbelief. Only after repeating the experiment several times were she and her Leipzig colleague—Svante Pääbo—convinced.

That a direct offspring of the two ancient humans was found among the first few fossil genomes recovered from the cave suggests, Pääbo says, “that when these groups met, they actually mixed quite freely with each other.”

The Daily Galaxy, Andy Johnson, via Science and The New York Times

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