Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig led a team that had to overcome daunting technical obstacles to produce the draft of the Neanderthal genome. He was assisted by the company 454 Life Sciences, which invented a new DNA decoding machine that works by analyzing millions of very small fragments of DNA in parallel. DNA from Neanderthal bones is fragmented in just this way.

Dr. Pääbo began his project more than 10 years ago, when he succeeded in extracting the first verifiable piece of Neanderthal DNA. Most Neanderthal bones have no recoverable DNA and those that do are heavily contaminated with modern human DNA from the many scientists and curators who handled them. Distinguishing human and Neanderthal DNA is hard because they are so similar.

He said at a news conference in Leipzig on Thursday that he now had retrieved usable DNA from six Neanderthals and analyzed 3.7 billion units of DNA. The Neanderthal genome, like that of modern humans, is 3.2 billion units in length. Because many units have been analyzed several times over, and many not at all, Dr. Pääbo can now see about 63 percent of the Neanderthal genome. He will continue to analyze it until he has accumulated the equivalent of 20 Neanderthal genomes, which will allow almost every unit to be accurately known.

An earlier analysis of Neanderthal DNA by Dr. Pääbo proved to have had 10 percent human contamination, he said, but in the new draft genome, he has taken pains to measure the degree of human contamination and finds it is below 3 percent, he said.

Archaeologists have long debated whether Neanderthals could speak, and they have eagerly awaited Dr. Pääbo’s analysis of the Neanderthal FOXP2, a gene essential for language. Modern humans have two changes in FOXP2 that are not found in chimpanzees, and that presumably evolved to make speech possible. Dr. Pääbo said Neanderthals had the same two changes in their version of the FOXP2 gene. But many other genes are involved in language, so it is too early to say whether Neanderthals could speak.