Monday, April 16, 2007

Chimps more evolved?   posted by Razib @ 4/16/2007 03:00:00 PM

The times has a mildly stupid article up, Chimps are ahead of humans in the great evolutionary race, which just goes to show that the people writing the headlines often have no comprehension skills, or just don't bother reading more than the first paragraph of a story. As confused as the article is it contradicts such a stark assertion. Here's the important point:
They found 154 human genes that showed evidence of the rapid positive selection that marks out adaptive traits, but 233 chimp genes with the same qualities.

Read the article with great caution, some of the sentences are very confused. That being said, I'm less interested in the raw count of differences in regards to evidence of positive selection (which can be sensitive to the test you're using, for example), then what differences exist between the loci in question. If the authors had found something suggestive I'm assuming they would have trumpeted it. Here's the journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0701705104, so keep an eye out for it (the lab's website gives the title as More genes underwent positive selection in chimpanzee evolution than in human evolution). I'm assuming that this will be the link: Also, here's something that caught my attention:
It is also possible that there are more adaptive genes in the human genome that have been positively selected, but that these emerged too recently to have been detected by the study.


Update: Much more intelligible article in ScienceNow. More details about the paper:
...the fast-evolving genes in humans and chimpanzees do not readily account for the obvious physical differences between the two species, Zhang points out. In the chimp, genes that have outpaced those in humans include ones involved in protein metabolism, gene transcription, and stress response. "You wouldn't immediately notice if the chimpanzee has a better stress response than a human," says Zhang. In the human, too, the differences appear to be subtle, with selection working rapidly on genes concerned with fatty acid metabolism and phosphate transport.
But that's not the whole story, argues Ajit Varki, a physician-scientist at the University of California, San Diego. "It's a terrific paper, but they're only looking at one mechanism, the changing amino acids in proteins. Other mechanisms in gene evolution--such as gene expression, duplication, conversion, and inactivation--are likely to be equally important." Further, Varki adds, these types of genomewide analyses are limited, because they do not address the issue of gene function. "It could be that the deletion of a specific gene or a single amino acid change could have more biological significance than a large number of genes that seem to have undergone many changes." And that means we're still a long way from explaining what makes us human--or them chimpanzee, he says.

Regular readers will know that exploring differential gene expression and copy number are hot fields that are coming to the fore. I assume that the paper itself will be a little less annoying than these overwrought popular press articles.

(yes, I'm not even addressing the orthogenetic or chain of being talking points, who cares? That's for the general public)

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