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LANGUAGE GENE IS TRACED TO EMERGENCE OF HUMANS
By Nicholas Wade
New York Times
August 15, 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
The finding supports a novel theory advanced by Dr. 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 Dr. 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
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.
Dr. 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 being published online today by the journal Nature, Dr. Paabo
says the FOXP2 gene has remained largely unaltered during the evolution of
mammals, but suddenly changed in humans after the hominid line had 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, Dr. 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.
Dr. 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," Dr. Paabo said.
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, Dr. Paabo has estimated
the age of the human version of FOXP2 as being less than 120,000 years.
Dr. Paabo says this date fits with the theory advanced by Dr. 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 Dr. 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.
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