FOXP2 gene shows why we can talk, but chimps can’t answer back

chimp_thinking

From The Times, November 12, 2009

By Mark Henderson, Science Editor

Two tiny changes in a gene linked to language may help to explain why people can speak and animals cannot, new research has shown. Though the gene, known as FOXP2, differs only very slightly between human beings and chimpanzees, scientists have discovered how these small variations unleash a cascade of other genetic effects that probably contributed to our species’ unique capacity for language. The study, published in the journal Nature, promises fresh insights into speech and language disorders as well as other conditions such as autism and schizophrenia.

“We showed that the human and chimp versions of FOXP2 not only look different but function differently too,” said Daniel Geschwind, of the University of California Los Angeles, who led the research. “Our findings may shed light on why human brains are born with the circuitry for speech and language and chimp brains are not. This has opened up a window through which we can look out on to the landscape of language.”

The study also highlights a means by which the very few genetic differences between closely related species such as humans and chimps create large differences in physiology, appearance and mental capacity. Many of the genes that make us human may work like FOXP2, serving as switches that turn entire networks of other genes on and off, greatly magnifying their overall effect on our bodies and minds.

While FOXP2 is not the “language gene” — many other genes are involved — it is the only gene that has so far been reliably associated with human language. It was identified in 2001 in a study of a British family known by the initials KE. About half of the family members have a severe language deficit that leaves them struggling to form and identify speech sounds, to construct sentences and understand grammar. When scientists from the University of Oxford examined their DNA they found affected members all had a mutation in FOXP2.

Further research then revealed that while the FOXP2 gene is almost identical in most mammals and birds, humans have a subtly different version. The protein made by human FOXP2 differs by just three amino acids from that of mice, and two of these changes have emerged since the evolutionary split from chimps about seven million years ago. The changes emerged about 200,000 years ago, when modern Homo sapiens emerged.

Dr Geschwind’s research has shown that these small changes in FOXP2 have a direct effect on its function. The scientists identified 61 genes that were turned up and 55 that were turned down by human FOXP2, but not by the chimp variant. Some of these genes are known to be involved in the way the brain controls motor function, and formation of the skull, face, cartilage and connective tissue.

Geldspenden in einem Tempel in Angkor Wat

The findings indicate that human FOXP2 may be guiding the activity of other genes in ways that let the brain, mouth muscles, vocal cords and breathing system control speech and language. The research suggests “an important role for human FOXP2 in establishing both the neural circuitry and physical structures needed for spoken language”. By pointing to other genes that might be implicated, the study will assist research into speech and language disorders and other conditions characterised by communication deficits, such as autism.

Way with words

— Several animals, such as bees and dolphins, have complex communications systems, but only human beings have language

— Chimpanzees, orang-utans and gorillas have been taught to use and understand sign language, but cannot construct these grammatically. Some birds, such as parrots, can mimic human speech, but without understanding its content

— Accepted properties of true language include grammatical structure, and the use of meanings for words that are not affected by the way they are vocalised, unlike a monkey’s alarm howl

— Human speech and language rely on several physiological and neurological traits, including advanced brain circuits, fine motor control of facial and breathing muscles, and the anatomy of the neck and face

— As language leaves no trace, the date of its emergence is unknown. Most scientists agree it must have begun 100,000 to 50,000 years ago, when Homo sapiens started producing figurative art that would have required language

— Another open question is whether Neanderthals had language. Their anatomy and genetic studies indicating that they had the same version of the FOXP2 gene as Homo sapiens, suggests this is possible

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vgl. New York Times, 12. 11. 09: http://www.nytimes.com/2009/11/12/science/12gene.html?_r=1&ref=science

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~ von Panther Ray - November 12, 2009.

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