Genome scan shows human-chimp differences
Variations hint at how our lifestyle is reflected in our genes.
12 December 2003
JOHN WHITFIELD

Genes involved in smell and hearing are significantly different between
humans and chimpanzees, researchers have discovered. The finding could be a
starting point for understanding what separates us from our closest
relative.

"This tells us the types of genes that are important for our differences,"
says Michele Cargill of the biotech company behind the comparison, Celera
Diagnostics in Alameda, California. But the list does not tell us what makes
us human, she cautions: "Just finding a change in one protein gives us no
idea of how it affects the whole animal."

The human and chimp genomes are about 99.2% identical. In the most important
bits of the genome, this figure rises to 99.5%. Yet Cargill and her
colleagues believe that they have seen the fingerprint of evolution in these
small DNA differences.

The researchers compared the sequences for more than 7,500 human, chimpanzee
and mouse genes, compiled by the genome projects for each species. Matching
the two primates against the mouse revealed whether chimp or man has changed
most from the ancestral starting point shared by the three mammals.

All DNA sequences change over time as mutations build up. To spot the
effects of evolution, the researchers looked for genes that had altered more
during the five million years since human and chimpanzee split than would be
expected by chance. About 1,500 genes seem to have been affected by
selection, this analysis showed.

"It's the first genome-wide comparison of humans and chimps," says
geneticist Svante Paabo of the Max Planck Institute for Evolutionary
Anthropology in Leipzig, Germany. "It will allow us to form many interesting
hypotheses about the crucial new features during human evolution."

But some scientists doubt that the differences studied are the work of
evolution. There are so few changes between human and chimpanzees, argues
evolutionary biologist Adam Eyre-Walker, that comparing single genes gives
hardly anything to analyse.

"My gut feeling is that there aren't enough data here," says Eyre-Walker,
who works at the University of Sussex, UK. He feels that it would be better
to combine information from many genes

Read the rest at Nature
http://www.nature.com/nsu/031208/031208-15.html

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