Neanderthals may have disappeared 40 thousand years ago, but they are no strangers to us today. However, there is no such familiarity with the Denisovans, humans who split from the Neanderthal lineage and survived for hundreds of thousands of years before becoming extinct.
This is largely because we have very few of his bones. In a new review, anthropologists counted all the fossils that have been clearly identified as Denisovan since the first one in 2010: a broken half jaw, a finger bone, a skull fragment, three loose teeth and four other bone chips.
“It's almost nothing,” said Janet Kelso, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology, in Leipzig, Germany, who helped write the test.
However, many scientists are increasingly fascinated by Denisovans. Like us, they were extraordinarily resilient. And billions of people on Earth carry Denisovan DNA.
“From a behavioral perspective, they were much more like modern humans,” said Laura Shackelford, a paleoanthropologist at the University of Illinois.
The Denisovans get their name from the Denisova Cave in Siberia, where their remains were first identified.
A molar between 122,700 and 194,400 years old contained genes similar to those of the Neanderthal, but its DNA was different enough to suggest it came from a separate branch of evolution. A finger bone dating from between 51,600 and 76,200 years ago belonged to the same lineage, showing that it existed for tens of thousands of years, if not longer.
Since then, researchers have found more Denisovan fossils in the cave and gathered loose genetic material from the cave floor, dating back 50,000 to 200,000 years.
Kelso and his colleagues came to suspect that the Denisovans had not been limited to Siberia. The researchers found that some stretches of ancient humans' DNA closely matched genetic material carried by people from East Asia, Native Americans, Aboriginal Australians, and people from New Guinea and other islands in the area.
When modern humans expanded out of Africa about 60,000 years ago, the Denisovans must have been on their way to interbreed and introduce some of their genes into our lineage.
In 2019, scientists found the first fossil trace of Denisovans beyond Siberia, in a high-altitude cave in Tibet — a jawbone dating back more than 160,000 years with teeth similar to Denisovans. It also contained proteins with a molecular structure that might be expected from a Denisovan. The following year, researchers reported that the cave floor contained Denisovan DNA.
Other researchers are studying Denisovan DNA inherited by living people. The pattern of mutations documented so far suggests that several genetically distinct groups of Denisovans interbred with our ancestors. And none of those Denisovan groups were closely related to those who occupied Denisova Cave.
These findings suggest that Denisovans thrived in radically different environments.
The Denisovans' versatility may have helped them last a long time. The people of New Guinea may have inherited some Denisovan DNA from interbreeding just 25,000 years ago.
The genetic legacy of the Denisovans lives on. Certain Denisovan genes have become more common because they provide an evolutionary advantage in modern humans. In Tibet, researchers have found a Denisovan gene that helps people survive at high altitudes.
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