White hot Fox

The first of the three mutations, presumably in an ancestral primate, occurred too long ago to estimate its age. The second and third mutations are quite recent, and exclusive to humans: their absence from chimpanzees, bonobos and gorillas means they occurred after the human and chimp lineages diverged around seven million years ago.

Przeworska estimated that Mutation No 2 occurred soon after the human-chimp divergence, hinting that FOXP2 may have had an influential role in the split. A newly acquired capacity for complex vocalisation would have been invaluable as our ancestors abandoned their aboreal niche in the African rainforest to exploit a new resource-rich but hazardous savannah-woodland environment.

Przeworska's estimate involved some rubbery assumptions about the size of human populations, reproductive age and reproductive success. It indicated that the third and most recent FOXP2 mutation occurred only 100,000 to 200,000 years ago - around the time that humans are thought to have developed the capacity for complex language.

It was too recent by half: last October, Svante Paabo's group achieved the remarkable feat of sequencing the first nuclear gene from a Neanderthal. They succeeded in recovering and sequencing FOXP2 from a Neanderthal skeleton from a cave in northern Spain. It proved to be identical to that of modern humans.

The timing of the divergence of pre-modern humans and Neanderthals is uncertain: it could have been 365,000 years ago, or as long ago as 780,000 years. Fossils from Portugal and Spain complicate the issue, by providing clear evidence of interbreeding between modern humans and Neanderthals in Europe less than 40,000 years ago.

But if Paabo's Spanish fossil is the real McCoy, the clear implication is that Neanderthals possessed the neuromuscular control mechanisms to produce complex language at least 300,000 years ago.

This is approximately the time that early H. sapiens began making more sophisticated stone tools, after more than a million years of technological stasis. Something interesting seems to have happened to human brain function during the Middle Paleolithic Transition. With complex language, humans could progressively accumulate and transmit complex cultural knowledge to each succeeding generation.

With the PloSOne paper last September, the FOXP2 and bat evolution stories - two of my favourite science stories - intersected, in a most unexpected and intriguing way. The gene that made humans human seems also to have lit the evolutionary fuse for the development of ultrasonic vocalisation and echolocation in microbats.