12:01am

Thu December 23, 2010
Humans

Ancient Bone's DNA Suggests New Human Ancestors

DNA taken from a pinkie bone at least 30,000 years old is hinting at the existence of a previously unknown population of ancient humans. It's just the latest example of how modern genetic techniques are transforming the world of anthropology.

The pinkie bone in question was unearthed in 2008 from what's called the Denisova Cave.

"The Denisova Cave is in southern Siberia in the Altai Mountains in central Asia," says David Reich, a geneticist at Harvard Medical School in Boston. "This bone is the bone of a 6- to 7-year-old girl."

Reich and colleagues from the Max Planck Institute for Evolutionary Anthropology in Leipzig were able to extract DNA from the pinkie bone and sequence all 3 billion letters of DNA that made up this girl's genome. This is the second ancient genome this team has unraveled. The first was the Neanderthal genome announced earlier this year.

Closer To Neanderthals

Reich says there were several remarkable things about the group of people this girl is from, a group he and his colleagues call Denisovans.

"On the one hand it's a sister group to Neanderthals, which means that it's more closely related to Neanderthals on average than it is to modern humans," he says.

As he reports in the journal Nature, the other remarkable finding was that Denisovans' genome was more closely related to humans currently living in New Guinea than it was to genomes of people in Europe or Asia.

"What it means is that there was gene exchange between relatives of this Denisovan and the ancestors of New Guineans," says Reich.

In other words, as they left Africa, modern humans must have passed through the realm of the Denisovans, and had sex with some of the locals, on their way to Melanesia. And if you look at a map, the route from Africa to New Guinea does not go through Siberia, suggesting that the Denisovans may have lived over a quite a large swath of the globe.

Reich says for now, this pinkie bone is the only known Denisovan fossil. "I think the hunt should be on for more fossils and to understand the tools they used," he says.

Transforming Anthropology

Anthropologist John Hawks of the University of Wisconsin, Madison says DNA evidence is changing the way anthropologists work. "It's so much more than we knew from the fossil record. It's really like discovering something for the first time," he says. Hawks says genetic analysis will provide a much richer picture of life in the distant past.

For example, a group in Spain published a paper this week analyzing the DNA from 12 Neanderthals found in a single cave. The analysis suggested the men were all brothers or cousins, whereas the women had come from different bands.

"Looking at that one site, you've got this picture of the existence of a group and how they were related to each other," he says. "That's cool. That's the kind of stuff we have no access to in the archaeological record." Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.