Even as creatures become complex, evolution doesn't get any harder.

The findings, published yesterday in Nature, shed doubt on a creationist criticism of evolution: that adaptation must rapidly slow as creatures grow more complicated, making them less able to adapt to changing conditions.

Led by Yale University evolutionary biologist Gunter Wagner, researchers measured the cumulative effects of genetic mutations in mice. Would tweaking a gene affect many different unrelated traits, thus imposing a "cost of complexity"? Or would the genetic ripple be constrained?

The latter, found the researchers: the effects of mutations were indeed multiple, but largely limited to related characteristics. The researchers also found no relationship between effect strength and the number of affected traits. Some scientists have wondered whether these would vary inversely, further slowing the pace of adaptation in complex organisms.

"I think the main broader impact of this work is on the evolution-creationism debate," wrote Wagner in an email. "I would say the only intellectually interesting argument that the creationists are using, at least the scientifically more sophisticated ones, is that random mutation can not lead to the evolution of complex organisms. And there are interesting mathematical arguments that have been made to support that. But our results show that organisms found a way around that problem by restricting mutational effects on very narrowly confined parts of the organisms."

Pleiotropic scaling of gene effects and the 'cost of complexity' [Nature]

Image: Detail from a mural by Blu.*

Note: Several months ago, I wrote about a study of Scottish sheep that found a genetic relationship between hair color and reproductive fitness – two seemingly unrelated traits. Didn't that contradict

Wagner's findings? *

Wrote Wagner, "Not really, these surprising pleiotropies have been know ever since Genetics was established as a discipline. The real question is how frequent are those broad effects among a sample of gene mutations" – and these, he said, are not frequent at all, as shown in both his study and another published recently inEvolution.

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