Scientists find brain evolution gene
(AP)
Updated: 2006-08-17 11:10
Washington - Scientists believe they have found a key gene that helped the
human brain evolve from our chimp-like ancestors. In just a few million years,
one area of the human genome seems to have evolved about 70 times faster than
the rest of our genetic code. It appears to have a role in a rapid tripling of
the size of the brain's crucial cerebral cortex, according to an article
published Thursday in the journal Nature.
Scientists believe they have found a key gene that helped the human
brain evolve from our chimp-like ancestors. In just a few million years,
one area of the human genome seems to have evolved about 70 times faster
than the rest of our genetic code. This 1999 file photo shows Shaun, a
male chimpanzee at the Los Angeles Zoo. [AP
Photo] | Study co-author David Haussler, director
of the Center for Biomolecular Science and Engineering at the University of
California, Santa Cruz, said his team found strong but still circumstantial
evidence that a certain gene, called HAR1F, may provide an important answer to
the question: "What makes humans brainier than other primates?" Human brains are
triple the size of chimp brains.
Looking at 49 areas that have changed the most between the human and
chimpanzee genomes, Haussler zeroed in on an area with "a very dramatic change
in a relatively short period of time."
That one gene didn't exist until 300 million years ago and is present only in
mammals and birds, not fish or animals without backbones. But then it didn't
change much at all. There are only two differences in that one gene between a
chimp and a chicken, Haussler said.
But there are 18 differences in that one gene between human and chimp and
they all seemed to occur in the development of man, he said.
Andrew Clark, a Cornell University professor molecular biology who was not
part of Haussler's team, said that if true, the change in genes would be fastest
and most dramatic in humans and would be "terrifically exciting."
However, the gene changed so fast that Clark said that he has a hard time
believing it unless something unusual happened in a mutation. It's not part of
normal evolution, he said. Haussler attributed the dramatic change to the stress
of man getting out of trees and walking on two feet.
And it's not just that this gene changed a lot. There is also its involvement
with the cerebral cortex, which is responsible for some of the more complex
brain functions, including language and information processing.
"It looks like in fact it is important in the development of brain," said
co-author Sofie Salama, a research biologist at Santa Cruz who led the efforts
to identify where the gene is active in the body.
The scientists still don't know specifically what the gene does. But they
know that this same gene turns on in human fetuses at seven weeks after
conception and then shuts down at 19 weeks, Haussler said.
|
