"I've always been interested in how the brain controls complex behaviors, and I became most interested in speech," Jarvis said. But it's hard to study speech in humans -- you can't keep someone in a lab for their entire life or perform invasive experiments on them. Non-human primates are usually the best choice for study, but other primates don't learn to mimic vocal sounds the way humans do.
But birds fit the bill.
Because the way birds learn to sing specific song patterns seems to mimic the way humans learn to form words (even some of the brain regions involved are known to be the same), Jarvis and his colleagues hoped that similar genes would be involved in the process, too.
Several papers on vocal learning in birds were released as part of the genome study, but Jarvis's favorite is one that describes how a computational biologist in his lab crunched all of the data sets together to find genes that lined up between birds. They found a consistent set of around 50 genes that seem to correlate with vocal learning: If a gene was more active in humans, it was also more active in birds who could learn songs (and the same held true if the gene was less active). These changes weren't seen in birds who don't learn songs or in non-speaking primates.
So when it comes to certain parts of the brain, singing birds have more in common genetically with humans than they do with other birds. The researchers believe that changes in these genes, which are involved in forming connections in the brain, make the difference between animals that can speak and ones that can't.
Bird and human speech probably evolved from the same ancient brain structure, Jarvis said, though this evolution happened in parallel -- not in a common ancestor. "It's like taking a brain circuit that controls your ability to learn how to walk and hooking it up to your vocal muscles," Jarvis said. He believes these connections allowed speech -- and birdsong -- to form.
Now that Jarvis and his colleagues know how similar the genetics of "speech" are in humans and birds, they can more confidently use birds to study humans. They can also use these genes to try to make animals who can't form speech sounds do so.
You shouldn't expect any "Planet of the Apes"-type language learning from non-human animals anytime soon, but these discoveries will be useful in pinpointing the origins and limits of our own vocal learning abilities.