A small bone fragment from the Denisova Cave in Siberia offers new evidence that Denisovans and Neanderthals mated. Credit: Thomas Higham University of Oxford
The closest known extinct relatives of modern humans were the thick-browed Neanderthals and the mysterious Denisovans. Now, a bone fragment from a Siberian cave, perhaps of a teenage girl, it is shown that the first hybrid of these groups, a new study concludes. The finding confirms cross that was only hinted at in earlier genetic studies.
A number of the now extinct human generations not only lived alongside modern man, but even interbred with them, allowing the traces of their DNA in the modern human genome. These lines are included the stocky Neanderthals, as well as the enigmatic Denisovans, known only from a few teeth and bone excavated in the Denisova Cave in the Altai Mountains. [In Images: The First Bone of a Neanderthal-Denisovan Hybrid]
Archaeological excavations have shown that the Neanderthals and the Denisovans included in Eurasia, with Neanderthal bones ranging from 200,000 to 40,000 years old have been excavated, particularly in western Eurasia and Denisovans until now only known from fossils, ranging from 200,000 to 30,000 years old found in east Eurasia. Prior work excavated Neanderthal remains in the Denisova-Cave, raising questions on how closely they interacted.
“A Neanderthal and a Denisovan genetically further from each other than two people who are now living,” study co-author Viviane Slon, a paleogeneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, said in an email to Live Science. “So we do not think that they met each other very often.”
The scientists examined a 1-inch-long (2.5 centimeters) of bone fragment, called “Denisova 11,” that archaeologists in 2012 in the Denisova-Cave. This shard came from a long bone such as a tibia or a femur, but scientists know little else about.
“You can’t even tell whether it is a human or animal by looking at it,”study senior author Svante Pääbo, an evolutionary geneticist at the Max Planck Institute for Evolutionary Anthropology, told Science in a phone call.
The researchers analyzed proteins extracted from Denisova 11 and more than 2,000 other bone fragments of the Denisova Cave, which showed that the fragment is from a human. The thickness of the outer part of the bone suggested that Denisova 11 belonged to a woman who was at least 13 years old when she died, while radiocarbon dating suggested Denisova 11 was more than 50,000 years old.
The scientists then ground to a powder is an example of Denisova 11 and the DNA of the bone substance.
Previous genetic research has shown that the Neanderthal and the Denisovan of judah declined more than 390,000 years ago, the researchers said. Genetic studiesalso alluded to the intersection between the Neanderthals and the Denisovans, but the extent to which they bastard was unclear, Live Science reported earlier.
“I never thought we would be as happy as an actual offspring of the two groups,” Slon said in the e-mail.
The researchers also found that the Denisovan father of the individual Denisova 11 had at least one ancestor of the Neanderthal, possibly as far back as 300 to 600 generations for his life. “So, from this single genome, we are able to detect multiple instances of interactions between Neandertals and Denisovans,” study co-author Benjamin Vernot, a population geneticist at the Max Planck Institute for Evolutionary Anthropology, said in the statement.
In addition, the scientists discovered that the teenage girl the Neanderthal mother was genetically more similar to the Neanderthals of Western Europe than to other Neanderthals who lived earlier in the Denisova-Cave. This suggests that Neanderthals migrated between western and eastern Eurasia for tens of thousands of years.
So far, scientists have sequenced the genome of only six people from the Denisova Cave. That one of these was the Neanderthal man and Denisovanparents, from a statistical point of view, that interbreeding may have been common when these groups interact, said Pääbo. “It makes you believe that when these groups meet, they have mixed freely with each other,” he said.
All in all, these findings suggest that modern humans, Neanderthals and Denisovans mixed when they encountered each other, said Pääbo. “The neanderthals and the Denisovans may have vanished, but only because they were recorded in modern human populations.”
The researchers are continuing to look for the oldest human DNA, not only in the thousands of other bone fragments in the Denisova-Cave, but of the sediments, that is there too.
“It’s nice to think that there are probably many more discoveries to be made from remains found at the site,” Slon said.
The scientists published their findings online today (Aug. 22) in the journal Nature.