Genome study of cave bones reveals early human hybrid
Although Homo sapiens won the world domination contest, we weren't without our competitors. For thousands of years we shared the planet with other hominin species, such as the Neanderthals and Denisovans. These early humans were known to have fought, competed and even cross-bred when they crossed paths, and now the most direct evidence of those meetings has been found. By sequencing the genome of a hominin bone from a Siberian cave, anthropologists have discovered the direct descendant of a Neanderthal and a Denisovan.
Neanderthals were a lot like us, but stockier, stronger and probably hairier. They inhabited Europe long before we modern humans trekked out there, and their range stretched into southwest Asia and as far north as Siberia. Denisovans lived around the same time, ranging from Siberia to Southeast Asia, although we don't know as much about them since all we have are a few teeth, finger and toe bones.
Genetic studies have revealed that these two species interbred with each other – and modern humans. Around two percent of the modern human genome is estimated to contain Neanderthal DNA, while some humans may be up to six percent Denisovan. But the two of them are far closer to each other than to us – possibly up to 17 percent of the Denisovan genome comes from Neanderthals.
Researchers from Max Planck have now conducted genetic analysis of a small bone fragment found in Denisova Cave in Russia, where most Denisovan remains have been found so far. The team discovered that the bone belonged to a female of at least 13 years of age, but it was her parents that were most interesting to the crew – her mother was a Neanderthal and her father a Denisovan.
"We knew from previous studies that Neanderthals and Denisovans must have occasionally had children together," says Viviane Slon, a first author of the study. "But I never thought we would be so lucky as to find an actual offspring of the two groups."
By studying this individual's genome, the researchers were able to learn more about the parents. In an unexpected twist, the mother turned out to be a closer genetic match to a distant Neanderthal population in western Europe, rather than another individual that had lived earlier in Denisova Cave. On the father's side of the family tree, the Denisovan apparently had at least one Neanderthal ancestor himself, suggesting the two species must have met in the past.
"It is striking that we find this Neanderthal/Denisovan child among the handful of ancient individuals whose genomes have been sequenced," says Svante Pääbo, lead author of the study. "Neanderthals and Denisovans may not have had many opportunities to meet. But when they did, they must have mated frequently – much more so than we previously thought."
The research was published in the journal Nature.
Source: Max Planck Institute