Aside from not knowing what the gene variants actually do, no one knows how precise the model Lahn used to date them is, Collins added.Lahn's own calculations acknowledge that the microcephalin variant could have arisen anywhere from 14,000 to 60,000 years ago, and that the uncertainty about the ASPM variant ranged from 500 to 14,000 years ago.Gray and Atkinson analysed 87 languages from Irish to Afghan.Rather than compare entire dictionaries, they used a list of 200 words that are found in all cultures, such as 'I', 'hunt' and 'sky'.For the microcephalin gene, the variation arose about 37,000 years ago, about the time period when art, music and tool-making were emerging, Lahn said.For ASPM, the variation arose about 5,800 years ago, roughly correlating with the development of written language, spread of agriculture and development of cities, he said.That does not mean one population is smarter than another, Lahn and other scientists stressed, noting that numerous other genes are key to brain development.
Other scientists urge great caution in interpreting the research.
That the genetic changes have anything to do with brain size or intelligence "is totally unproven and potentially dangerous territory to get into with such sketchy data," stressed Dr.
Francis Collins, director of the National Human Genome Research Institute.
The work was funded by the Howard Hughes Medical Institute. A family tree of Indo-European languages suggests they began to spread and split about 9,000 years ago.
The finding hints that farmers in what is now Turkey drove the language boom - and not later Siberian horsemen, as some linguists reckon.