> Evolution gave us something to talk about
>
>
> By Nicholas Wade
> NEW YORK TIMES NEWS SERVICE
>
> August 21, 2002
>
>
> A study of the genomes of people and chimpanzees has yielded a deep
> insight into the origin of language, one of the most distinctive human
> attributes and a critical step in human evolution.
>
> The analysis indicates that language, on the evolutionary time scale,
> is a very recent development, having evolved only in the last 100,000
> years or so.
>
> The finding supports a novel theory advanced by Richard Klein, an
> archaeologist at Stanford University, who argues that the emergence of
> behaviorally modern humans about 50,000 years ago was set off by a
> major genetic change, most probably the acquisition of language.
>
> The new study, by Svante Paabo and colleagues at the Max Planck
> Institute for Evolutionary Anthropology in Leipzig, Germany, is based
> on last year's discovery of the first human gene involved specifically
> in language.
>
> The gene came to light through studies of a large London family, well
> known to linguists, 14 of whose 29 members are incapable of articulate
> speech but are otherwise mostly normal.
>
> A team of molecular biologists led by Dr. Anthony P. Monaco of the
> University of Oxford last year identified the gene that was causing
> the family's problems. Known as FOXP2, the gene is known to switch on
> other genes during the development of the brain, but its presumed role
> in setting up the neural circuitry of language is not understood.
>
> Paabo's team has studied the evolutionary history of the FOXP2 gene by
> decoding the sequence of DNA letters in the versions of the gene
> possessed by mice, chimpanzees and other primates – and people.
>
> In a report published by the journal Nature, Paabo says the FOXP2 gene
> has remained largely unaltered during the evolution of mammals, but it
> suddenly changed in humans after the hominid line split off from the
> chimpanzee line of descent.
>
> The changes in the human gene affect the structure of the protein it
> specifies at two sites, Paabo's team reports. One of them slightly
> alters the protein's shape; the other gives it a new role in the
> signaling circuitry of human cells.
>
> The changes indicate that the gene has been under strong evolutionary
> pressure in humans. Also, the human form of the gene, with its two
> changes, seems to have become universal in the human population,
> suggesting that it conferred some overwhelming benefit.
>
> Paabo contends that humans must already have possessed some
> rudimentary form of language before the FOXP2 gene gained its two
> mutations. By conferring the ability for rapid articulation, the
> improved gene may have swept through the population, providing the
> finishing touch to the acquisition of language.
>
> "Maybe this gene provided the last perfection of language, making it
> totally modern," Paabo said.
>
> Sweeping changes
> The affected members of the London family in which the defective
> version of FOXP2 was discovered do possess a form of language. Their
> principal defect seems to lie in a lack of fine control over the
> muscles of the throat and mouth, needed for rapid speech. But in tests
> they find written answers as hard as verbal ones, suggesting that the
> defective gene causes conceptual problems as well as ones of muscular
> control.
>
> The human genome is constantly accumulating DNA changes through random
> mutation, though they seldom affect the actual structure of genes.
> When a new gene sweeps through the population, the genome's background
> diversity at that point is much reduced for a time, since everyone
> possesses the same stretch of DNA that came with the new gene.
>
> By measuring this reduced diversity and other features of a must-have
> gene, Paabo has estimated the age of the human version of FOXP2 as
> being less than 120,000 years.
>
> Paabo says this rough date fits with the theory advanced by Klein to
> account for the sudden appearance of novel behaviors 50,000 years ago,
> including art, ornamentation and long-distance trade. Human remains
> from this period are physically indistinguishable from those of
> 100,000 years ago, leading Klein to propose that some genetically
> based cognitive change must have prompted the new behaviors. The only
> change of sufficient magnitude, in his view, is acquisition of
> language.
>
>
>
>
> Copyright 2002 Union-Tribune Publishing Co.
This archive was generated by hypermail 2b30 : Sun Sep 22 2002 - 05:06:20 MDT