"Five genes stood out as different in Neanderthals and modern humans. One of them has to do with how sperm cells whip their tails around. Another relates to wound-healing. Yet another builds a protein for the skin, sweat glands and hair roots. "It's tantalizing to think that the skin changed, but the biological implication of that is not at all clear yet," Pääbo said.

Several genes showed evidence of positive selection in humans as opposed to Neanderthals - including genes linked to schizophrenia, autism and Down syndrome. "This suggests that some of the genes that were positively selected may have had to do with cognitive development. ... It doesn't suggest that Neanderthals had no autism, or that they were more similar to people with autism," Pääbo said.

The researchers also focused on a gene that was linked to development of the frontal part of the skull, the shoulder bone and ribcage. Those are anatomical features where Neanderthals and humans differ, so the researchers said it was a "reasonable hypothesis" that that particular gene, RUNX2, "was of importance in the origin of modern humans."

Researchers are continuing to analyze the Neanderthal genetic data, and they expect to get a clearer picture of the species distinctions as time goes on.

Right now, the coverage of the genome is 1.3x, which means an individual DNA base pair was checked only 1.3 times on average. Pääbo said "our goal for the next two to three years is to come somewhere between 10 and 20x coverage," which would be comparable to the accuracy for a typical human genome. He estimated the cost of the project so far at 2 million to 3 million euros ($2.5 million to $3.8 million), but added that "it will be a lot cheaper to now go on."

Tattersall said the research team's first draft was "a remarkable achievement, and something they should be congratulated for." And he expected that there would be even more remarkable revelations ahead.

"This is the beginning of the story," he told me, "not the end of it."