FOXP2 has (perhaps a little over-enthusiastically) been called the “speech and language gene”. It exists in non-human animals, and without it, people don’t speak well, zebra finches don’t learn or sing songs well, and mice don’t squeak very well.

FOXP2 is now in the news. A team of researchers has given a human FOXP2 gene to a mouse. (Apparently chimps were a no-go.)

Researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have now genetically engineered a strain of mice whose FOXP2 gene has been swapped out for the human version. Svante Paabo, in whose laboratory the mouse was engineered, promised several years ago that when the project was completed, “We will speak to the mouse.”

He did not promise that the mouse would say anything in reply, doubtless because a great many genes must have undergone evolutionary change to endow people with the faculty of language, and the new mouse was gaining only one of them.

Yep, you’re not going to get talking mice just like that. Human speech has been built up over the years from at least two important factors:

• Cognitive horsepower. Before you can talk, you have to have something to say. Miss Perfect’s dog doesn’t need speech; it can already communicate everything in its tiny dog brain by the usual means: whimpering, plaintive dog-looks, and above all the constant and ceaseless barking barking barking. If the dog were under some selectional evolutionary pressure to communicate, it might do it some good to upgrade its hardware to include the capability for abstract symbol manipulation, which is one way to regard language. Language and brainpower have probably contributed to each other. Michael Arbib, among others, argues that the stages on the way to human language (recognition of others’ actions, gesture, and so forth) helped to increase our brainpower, which in turn helped to improve our capacity for language, and on and on until here we are.
• Vocal tract. The human vocal tract can make a lot of distinct sounds, which is what you’d want. A good range of sounds makes it easy to have words that sound distinct from each other, which brings down the cognitive brainpower necessary to use a spoken language. The human vocal tract isn’t a straight pipe; it’s bent into an L-shape, possibly because of our bipedalism. This shape contributes to our ability to make a range of sounds.

So, to get a mouse to speak, you’re going to need to do more than add a gene here and there. There’s a lot of infrastructure to add.

But the addition of human POXP2 does some interesting things to the mice:

In a region of the brain called the basal ganglia, known in people to be involved in language, the humanized mice grew nerve cells that had a more complex structure and produced less dopamine, a chemical that transmits signals from one neuron to another. Baby mice utter ultrasonic whistles when removed from their mothers. The humanized baby mice, when isolated, made whistles that had a slightly lower pitch, among other differences, Dr. Enard says.
…
Dr. Gary Marcus, who studies language acquisition at New York University, said the mouse study showed lots of small effects from the human FOXP2, which fit with the view that FOXP2 plays a vital role in language, probably along with many other genes that remain to be discovered.

“People shouldn’t think of this as the one language gene but as part of broader cascade of genes,” he said. “It would have been truly spectacular if they had wound up with a talking mouse.”