Turning to Neanderthal bones, they have already recovered considerable amounts of DNA sequence, which are derived from every chromosome in the Neanderthal cell, as judged by matching the Neanderthal DNA to the human genome sequence that was first fully decoded in 2003.

The first goal of the project will be to sequence three billion units of Neanderthal DNA, corresponding to the full length of the Neanderthal genome. This will require decoding 20 times as much DNA, because so much of the DNA in the Neanderthal bones belongs to bacteria.

Genomes must usually be decoded several times over to get a complete and accurate sequence, but the first three billion bases of Neanderthal should “hit all the essential differences,” Dr. Egholm said.

The researchers’ hope is to recover the entire sequence of the Neanderthal genome, but that will depend on which they can recover enough DNA. From sampling so far, no particular gaps in the sequence are apparent. “We are hitting all the chromosomes and getting good coverage,” Dr. Egholm said. If no single specimen yields a full sequence, the genome might be recovered by combining DNA from several individuals.

One of the most important results that researchers are hoping for is to discover, from a three-way comparison between chimp, human and Neanderthal DNA, which genes have made humans human. The chimp and human genomes differ at just 1 percent of the sites on their DNA. At 1 percent, Neanderthals resemble humans at 96 percent of the sites, to judge from the preliminary work, and chimps at 4 percent. Analysis of the DNA at the sites at which humans differ from the two other species will help understand the evolution of specifically human traits “and perhaps even aspects of cognitive function,” Dr. Paabo said.

The degree of resemblance between humans and Neanderthals is fiercely debated by archaeologists and even issues such as whether Neanderthals had language have not been resolved.

Dr. Paabo believes that genetic analysis is the best hope of doing so. He has paid particular attention to a gene known as FOXP2, which from its mutated forms in people seems to be involved in several advanced aspects of language. The human version of the gene differs at two sites from the chimp version. Knowing whether the sequence of the Neanderthal gene is closer to chimps or humans would help decide whether they had advanced speech like people or some lesser form of communication, perhaps without syntax.