Team pinpoints first gene key to language
The discovery, announced in Nature today by scientists in Oxford and London, was the climax of a 10 year hunt for the genetic roots of language. And it was identified with the help of a British family of three generations, of whom half spoke normally, and half had a severe language disorder.
Most children learn to marshal words and construct sentences accurately and unconsciously. The 24 members of the family studied by Faraneh Varga-Khadem at the Institute of Child Health in London, and Anthony Monaco of the Wellcome Trust Centre for Human Genetics in Oxford had a different experience.
About half of the boys and girls learned to speak normally, and at the normal age. The others had immense difficulty with mouth and tongue movements. They passed tests of non-verbal intelligence. But they had difficulty identifying the phonemes - the vowels and consonants of speech. And they had problems applying the basic rules of grammar. "They don't make the fine motor movements needed to produce speech sounds. But it is not just a motor problem," said Professor Monaco. "They don't develop language normally, they don't understand sentences, they don't use grammar properly."
Over the 10 years, scientists closed in on chromosome 7, and then on a gene already known to regulate other genes. Finally, they identified a telltale mutation in the afflicted members of the family. But the disovery is a beginning, not an end.
"SPCH1 cannot act alone, it will need to cooperate with other genes and proteins," said Prof Monaco.
But the SPCH1 mutation may not be at the root of either autism or the common forms of language impairment present in 4% of children.
Nor did the discovery raise immediate hopes of a possible treatment.
Researchers must first work out how one gene could trigger the changes in a series of genes in a way that would end in the puzzling and very rare inability to understand certain rules of grammar.
Steven Pinker, of the Massachusetts Insititute of Technology and author of the scientific bestseller The Language Instinct, writes in Nature that Charles Darwin had proposed 130 years ago that humans had an "instinctive" tendency to speak.