Decoded Neanderthal DNA lends clues

Using a 38,000-year-old bone fragment found in a Croatian cave, scientists have decoded a section of DNA from humanity’s closest related species – the long-extinct and enigmatic Neanderthal.

So far, researchers have sequenced about 1 million out of an estimated 3 billion base pairs of the Neanderthal genome. They expect it will take two years to complete a full draft.

But the reports, published concurrently today in the journals Nature and Science, demonstrate the feasibility of squeezing genetic information out of fossils – a new way of probing the ancient past that until now has been glimpsed primarily through scattered bones and artifacts.

A complete Neanderthal genome would help scientists zero in on a fundamental question: What makes humans human?

Even the preliminary sequences contain enough information to calculate that Homo neanderthalis and Homo sapiens shared at least 99.5 percent of their DNA.

The genetic analysis was not precise enough to pinpoint the first branching of the human and Neanderthal lineages. One group of researchers, which published the report in Science, estimated that the ancestors of humans and Neanderthals began to genetically diverge about 706,000 years ago. Another team publishing in Nature calculated the divergence occurred 516,000 years ago.

Fully evolved Neanderthals are thought to have arisen about 130,000 years ago, settling in Europe and western Asia. Modern Homo sapiens emerged at roughly the same time in Africa.

As humans pushed their way into Eurasia 40,000 to 50,000 years ago, they came in contact with their long-separated cousins. Within 10,000 to 20,000 years, the Neanderthals had disappeared.

One of the most hotly contested topics in paleoanthropology is whether the two species interbred while they both inhabited Europe and Asia. Scientists are eager to search for evidence of Neanderthal genes in human DNA and vice versa.