Neanderthals vanished about 30,000 years ago, leaving modern humans to inherit the Earth. Why humans ended up being more successful has long been a topic of debate.
The newly completed sequence shows that humans and Neanderthals have genomes that are 99.5 percent the same.
By comparing the human and Neanderthal genomes with that of our closest living relative, the chimpanzee, researchers hope to tell which genes changed very recently, giving modern humans an edge.
"Studying the Neanderthal genome will tell us what makes modern humans really modern, and really human," said project collaborator Jean-Jacques Hublin, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
Reading the Genome
An animal's genes are made up of base pairs, the "letters" of the genetic alphabet. Genes give organisms their physical traits, from hair color to body shape. By contrast, a genome is the full set of genes that gives rise to a particular species.
Sequencing the more than 3.7 billion base pairs in the Neanderthal genome took about four years. So far the team has read only about 60 percent of the genes.
The initial results, announced today at a press conference at the Max Planck Institute, show intriguing contrasts between us and our ancient cousins.
For example, the research supports previous studies of Neanderthal DNA that show we share the same version of a "language gene" called FOXP2, noted team leader Svante Pääbo, also of the Max Planck Institute.
This gene is involved in linguistic development, suggesting that Neanderthals could talk.
"Although there are many genes involved in language," Pääbo said, "there's no reason to say that they couldn't articulate the way that we do." In addition, the genome offers more proof that Neanderthals couldn't digest lactose as adults, a condition that today affects close to 50 million U.S. adults, according to the American Gastroenterological Association.
"We can see the Neanderthal was not able to drink milk, [after] they were weaned," Pääbo said.
Researchers plan to make more comparisons like this, for instance, by looking at genes involved in brain development.
"In humans, we have a lot of recent evolutionary changes," that could explain our species' differing intellects, said anthropologist John Hawks at the University of Wisconsin in Madison, who was not involved in the project.
"I'll be looking at whether there are parallel changes in the ancient Neanderthal lineage."