Croker Sack

"Democracy is the theory that the common people know what they want, and deserve to get it good and hard." — Henry Louis Mencken (1880-1956)

Wednesday, December 29, 2004

Special? Yes. But was it by design?

As reported today, the evolution of the human brain was unique among the creatures of Earth.

Note the scientists’ apparent focus on the role of natural selection as the driving force behind this “special event.”

Human Brain Evolution Was a 'Special Event'

Genes that control the size and complexity of the brain have undergone much more rapid evolution in humans than in non-human primates or other mammals, according to a new study by Howard Hughes Medical Institute researchers.

The accelerated evolution of these genes in the human lineage was apparently driven by strong selection. In the ancestors of humans, having bigger and more complex brains appears to have carried a particularly large advantage, much more so than for other mammals. These traits allowed individuals with “better brains” to leave behind more descendants. As a result, genetic mutations that produced bigger and more complex brains spread in the population very quickly. This led ultimately to a dramatic “speeding up” of evolution in genes controlling brain size and complexity.

“People in many fields, including evolutionary biology, anthropology and sociology, have long debated whether the evolution of the human brain was a special event,” said senior author Bruce Lahn of the Howard Hughes Medical Institute at the University of Chicago. “I believe that our study settles this question by showing that it was.”

Lahn and his colleagues reported their data in a research article published in the December 29, 2004, issue of the journal Cell.

It seems clear that the advantages which are associated with having a better brain would probably contribute to more frequent success in surviving to procreate, but those advantages would be enjoyed by any creature that had a better brain.

Why would the apparently rapid mutation rate have occurred only in humans?


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