The mutation seems to have helped humans develop speech and language. It's probably not the only gene involved, but researchers found the gene looks and acts differently in chimps and humans, according to a study published online Wednesday by the journal Nature.
Lab tests showed that the human version regulated more than 100 other genes differently from the chimp version. This particular gene - called FOXP2 - mutated around the time humans developed the ability to talk.
"It's really playing a major role in chimp-human differences," said the study's author, Daniel Geschwind, a professor of neurology, psychiatry and human genetics at the University of California, Los Angeles. "You mutate this gene in humans and you get a speech and language disorder."
This tells you "what may be happening in the brain," he said.
Frances Vargha-Khadem, head of developmental cognitive neuroscience at the University College London, who wasn't part of the research, said the study "is very much in line with what we had always suspected."
Vargha-Khadem has studied people with other inherited mutations in the gene and their speech and language problems. People with a certain mutation have subtle physical differences in the lower part of the jaw, the tongue and roof of the mouth, and she suspects chimps do, too.
That physical part is important because "you can't produce the dance unless you have the feet to do the dance," she said.
Eventually, work on this gene and others could potentially lead to genetic treatments for people with certain developmental difficulties, such as autism, because it gives future researchers targets, Geschwind said.
Other outside experts warned of making too much of this finding.
While finding the molecular differences is good, it is too early and unclear to weigh what it means for language and cognitive evolution, said Marc Hauser, a professor of human evolutionary biology at Harvard University.
"I would be extremely skeptical about drawing inferences," Hauser wrote in an e-mail.
And the key question is not how, but "why did we get language," said Derek Bickerton, a linguistics professor at the University of Hawaii. He wrote the book "Adam's Tongue: How Humans Made Language, How Language Made Humans."
Just because humans developed the ability for language, that doesn't mean it would happen automatically, Bickerton said.
"Every other species gets along just fine without it," Bickerton wrote in an e-mail. "We must have had some need that other species didn't have."