A previously unknown lineage of humans has been identified based on genes extracted from a bit of bone found in Siberia, scientists say.
The finding may represent a new species that lived alongside Neanderthal people and anatomically “modern” humans in that region, according to the researchers.
“I at first didn’t believe” that the result could be possible, said one of the researchers involved with the finding, Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany. However, Pääbo said, genetic test results showed “it’s some new creature that has not been on our radar screen so far.” The findings are published in the March 25 issue of the research journal Nature.
The conclusions were based on the sequencing, or decoding, of the organism’s “mitochondrial genome,” that is, DNA from a cellular structures called the mitochondria.
Mitochonchondrial DNA is not inherited the same way as the rest of an animal’s DNA, but rather is passed down only from the mother. Because unlike other DNA it remains relatively unchanged when passed down through generations, it plays an important role in ancestry studies, in particular in determining an organism’s mother-line ancestry.
The genetic sequencing pointed to a previously unknown hominin, or extinct member of the human lineage, who lived in the Altai mountains of southern Siberia between 48,000 and 30,000 years ago, said the researchers.
The investigating team, which included also researchers from the United States, Austria and Russia, sequenced genes from a tiny piece of pinky finger bone found in Denisova cave in the Altai Mountains. They compared the mitochondrial genome with that of modern humans and Neanderthals.
The analysis indicated that the creature shared a common female or “mitochondrial” ancestor with modern human and Neanderthals about a million years ago, the scientists said. That’s about twice as old as what is believed to be the most recent common mitochondrial ancestor of modern humans and Neanderthals. Neanderthals were a stocky, now extinct subgroup of our species, Homo sapiens, who lived in Europe and parts of Asia from around 100,000 to 30,000 years ago.
The age of the fossil and the layers of earth in which they turned up also suggest “the Denisova hominin lived close in time and space with Neanderthals as well as with modern humans,” the researchers wrote.
Although researchers said they lacked definitive enough information to declare the fossil a new species, they said it also likely represented a separate migration out of Africa from modern humans and Neanderthals, both of whom are thought to have originated in that continent. The investigators also said they have no information yet that could serve to physically describe any unusual characteristics that the newfound human ancestor might have possessed.
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