Back in 2001, FoxP2 was the first gene to be linked to human language. The gene was hunted down by studying a British family with extreme difficulties in forming speech. I wrote about (paywall) this work at the time.
Since then, there's been a bunch of studies on the gene - revealing, for example, relatively large differences between the human sequences and that of other primates. But it was thought that, humans aside, there was relatively little variation in vertebrates.
Well, just goes to show how taxonomically restricted our genetic knowledge is, because a Sino-Anglo team has just discovered that the gene varies lots in bats, which don't talk, but do echolocate. There's a news report about their PLoS One paper here.
To see how the variation between closely related bat species really does dwarf that seen between much more distantly related beasts, check out this figure.
Nice. But FoxP2 is not giving up all its secrets just yet. The pattern of evolution - what's been selected for what - is not clear from the sequences, there's just a lot of difference. And comparing bat sequences with other species doesn't help much
Evidence from birds, which likes bats and people show vocal learning, is shows 'no evidence of specific mutations associated with vocal learning abilities...if variation in FoxP2 has a role in vocal learning then it is not straightforward'. Nor are there clear similarities with whales, which also vocal learn and echolocate.
So what is FoxP2 uP2? If it's a 'language gene' it looks as if it's role isn't in what we think of as the clever stuff of language - grammar and syntax - but in the mechanics: the motor control needed to produce tightly controlled sounds, say. But, as far as I can tell, there's no hard and fast links between the gene sequence and this ability. It's just involved somewhere down the line.
One clue is that FoxP2 is a transcription factor - it's product controls the activity of other genes. Maybe this is why comparing species gives few clues as to how its sequence relates to its function: because it's an information processing gene and not making something like haemoglobin, the structure of which is jolly important, maybe its free to vary more, and to mean different things to different animals.
I don't know how much we know about the genes it regulates - I couldn't see anything in the paper, so I'm guessing not much.