



The discovery may also help scientists answer the vital question of when language evolved and whether the power it gave modern humans was the primary reason they flourished and spread rapidly around the world.

Some scientists, however, say they believe the gene may be less specific to language than it seems. So the new finding could simply fuel a longstanding debate among linguists as to whether the brain handles language through mechanisms specifically dedicated to the task or through a more general system.

The new discovery is described in today's issue of Nature by Dr. Anthony P. Monaco of the University of Oxford in England and colleagues.



The carriers of this variant gene resemble other people who have impairments of language. They came to researchers' attention in 1990 only because there were so many of them, all related and all living in the same area of London. The family now has 29 members in three generations, 14 of whom have the disorder.

The first linguist to study the family, Dr. Myrna Gopnik of McGill University in Montreal, reported in 1990 that affected members were unable to change the tense of verbs correctly, a finding that provoked considerable stir in the linguistic world because it implied the existence of genes for grammar.

But in a later study of the family, Dr. Faraneh Vargha-Khadem of the London Institute of Child Health identified a much wider range of speech and language deficits, and some effects on general intelligence. The variant gene "affects speech, but with knock-on effects in nonverbal ability," Dr. Vargha-Khadem said.

In 1998, Dr. Monaco and a team of geneticists at the University of Oxford started to search for the variant gene, or for the lack of a gene, that presumably caused the London family's disorder. They identified as the likely source of the problem a region on Chromosome 7, the seventh of the 23 pairs of giant molecules in which each human cell's DNA is packaged. But the region contained about 100 genes.

Settling down to the long chore of examining each of these genes in turn, Dr. Monaco's team had a lucky break when Dr. Jane A. Hurst, the clinician who first examined the London family, came across an unrelated patient with what seemed to her the same pattern of impairment.

The new patient had a visibly odd version of Chromosome 7, enabling Dr. Monaco to identify a specific defective gene. The same gene turned out to be the source of the London family's disorder as well, although in the family's case it is sabotaged in a different way.

The newfound gene's product is a protein that binds to different sites along the DNA, signaling the cell to activate the nearby genes. Identifying the set of genes that is switched on by the protein could yield a deep insight into how a distinctive faculty of the human brain is constructed.

The new gene "gives us an entry point into language," Dr. Monaco said.

Discovery of the gene may give scientists a means to address the longstanding question of when language evolved. Although some experts claim to see evidence for language in hominid skulls millions of years old, others note the absence of another form of symbolic representation — art — until much more recently. If the two evolved together, language must be a fairly recent human acquisition.

Dr. Richard Klein, an archaeologist at Stanford University, argues that a specific genetic change produced the modern human brain some 50,000 years ago and that this neural change was probably the one that made language possible.

The newly discovered gene may enable geneticists to test that hypothesis by comparing the role of the human gene with the counterpart gene in chimpanzees. Chimpanzees can learn signs but lack the ability to string them together in sentences, a uniquely human ability.

Dr. Monaco said he had started a collaboration with Dr. Svante Paabo of Leipzig, Germany, who is studying the chimpanzee and other primate genomes. The two researchers will measure the rate of evolutionary change the newfound gene has undergone in the different branches of the primate tree, looking for any recent spurt in the human version of the gene.

Dr. Klein's idea that a language gene preceded human modernity reflects the theory first advanced in 1959 by the linguist Noam Chomsky, that language ability is innate, implying that there is a dedicated language organ embedded in the brain's circuitry. Others argued that language arises from an array of more general purpose cognitive abilities.

Asked about the new finding, Dr. J. Bruce Tomblin, a language researcher at the University of Iowa, said that several variant genes that seemed at first to affect only speech had turned out to cause other cognitive problems as well and that the same might prove true of the new gene.

"I am inclined to think there probably aren't such things" as language or speech genes, Dr. Tomblin said.
