NY Times August 15, 2002
By NICHOLAS WADE 

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 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 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. 

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.