Scientists unravel DNA of 38,000-year-old Neanderthal

Scientists have obtained the most extensive DNA profile of Neanderthal man from a fragment of bone of an individual who died 38,000 years ago - a few thousand years before the entire species became extinct.

An analysis of the genetic material confirms that the Neanderthal in question was male and his species probably did not interbreed with anatomically modern humans - Homo sapiens.

The researchers who isolated and deciphered the sequence of the Neanderthal DNA said their findings indicate that Neanderthals diverged genetically from the ancestors of modern humans about 400,000 years ago. It is known that H. sapiens and H. neanderthalenis lived alongside each other in Europe and the Middle East for thousands of years before the Neanderthals eventually disappeared about 30,000 years ago.

Apart from the issue of what killed off the Neanderthals, the biggest unresolved question is whether the two human species interbred during the millennia when they shared the same habitat.

"While unable to definitively conclude that interbreeding between the two species of humans did not occur, analysis of the nuclear DNA from Neanderthal suggests the low likelihood of it having occurred at any appreciable level," said Edward Rubin of the Lawrence Berkeley National Laboratory in California. "We see no evidence of genetic mixing 30,000 or 40,000 years ago in Europe. We didn't exclude it, but from the evidence we have we see no evidence for it."

Two separate teams of researchers extracted DNA samples from a Neanderthal thigh bone excavated from a prehistoric cave site in Croatia. Dr Rubin's team extracted fragments of nuclear DNA about 65,000 base pairs long - the individual letters of the DNA code. Using a different approach, Svante Paabo, of the Max Planck Institute for Evolutionary Anthropology, in Leipzig, extracted a million DNA base pairs from the same bone specimen.

This is still less than 0.03 per cent of the entire Neanderthal genome but it nevertheless represents a significant achievement given the age of the bone and the amount of DNA contamination from bacteria and human handling. "Clearly we're at the dawn of Neanderthal genomics," said Professor Paabo. "There's no question in years to come that we will be able to sequence a Neanderthal genome. It is possible to use this process to go after the entire genome.

"We'll be able to use it to see whether Neanderthals contributed to the genetic variation of humans today, and whether early humans interacted and contributed to the genetic variation of the Neanderthals. Sequencing the Neanderthal genome offers the unique possibility to identify genetic changes specific to the genome of anatomically fully modern humans."

The two studies, published in the journals Science and Nature, represents a major step forward in understanding human origins, said Professor Chris Stringer, of the Natural History Museum, in London.

"Having such rich data holds the promise of looking for the equivalent genes in Neanderthals that code for specific features in modern humans, for instance eye colour, skin and hair type," he said. "Having a Neanderthal genome will also throw light on our own evolution, by allowing a three-way comparison of the genetic blueprints that produced Neanderthals, and that today produce us and our closest living relatives, the chimpanzees. We should then be able to pin down unique changes in each genome to show how we came to be different from each other."