Scientists Sequence Part of Neanderthal Genome

The results may shed light on human origins as well as answer questions about humans' ancient, long-extinct cousins. Neanderthals first diverged from humans around 500,000 years ago, and the two species coexisted in Europe and Asia until about 30,000 years ago.

Two research groups conducted separate analyses of the bone fragment and both published papers Friday -- one in the journal Science and the other in the journal Nature.

Edward Rubin, director on the Genomics Division at Lawrence Berkeley National Laboratory and one of the authors of the Science paper, told the Associated Press that the research will ''serve as a DNA time machine that will tell us about the biology and aspects of Neanderthals that we could never get [otherwise]."

It may also teach scientists more about what makes humans unique, by allowing them to figure out which genetic changes happened relatively late in human development, after the two species diverged.

So far, the two groups have sequenced about 1 million of the estimated 3 billion building blocks in the Neanderthal genome. Svaante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and an author of the Nature study, told the AP that he expects researchers will be able to map the rest of the Neanderthal genome in the next two years.

Sequencing Neanderthal DNA has proven challenging in the past for several reasons. First, DNA from ancient fossils is often degraded and difficult to work with. Second, fossil samples can be contaminated with modern human DNA from people who touch or handle the specimens. And because Neanderthal and human DNA is so similar, it can be difficult to tell the two apart. Luckily, Paabo told the AP, the Croatian sample had been left in a box in a Croatian museum and not handled much, so it wasn't as contaminated.

Both research groups found that the Neanderthal DNA was at least 99.5 percent identical to human DNA.

The two papers add to the recent scientific debate over whether humans and Neanderthals ever mated and interbred. Rubin said that his analysis found no evidence any such genetic mixing took place.

Paabo, however, told the AP that his analysis did not directly address the issue but that it did raise speculation that such interbreeding might have occurred. "Taken at face value, our data can be explained by gene flow from modern humans into Neanderthals," Paabo told Science's news section.