Blue Collar Scientist

For years, creationists have shrilly insisted that the more complex a life form is, the slower it could evolve adaptive traits. Supposedly this showed that evolution wouldn’t work, or something.

Of course, just bleating that something is true doesn’t make it so. And as in so many other cases when we are dealing with creationist rhetoric, this one isn’t true either.

Yesterday Nature published a paper with the inspiring title Pleiotropic scaling of gene effects and the ‘cost of complexity.’ The experiments described in the paper deliver a body-blow to the so-called “cost of complexity” hypothesis.

The researchers did something very straightforward - they caused mutations in mice, and then measured the results. If the “cost of complexity” crowd were right, then making a single genetic mutation should affect many different unrelated traits. If they were wrong, then the effects would be limited to either a single trait, or several related traits. The researchers found that the latter was the case.

A more technical way of discussing the findings is to say that pleiotropies are rare. A pleiotropy exists when a single gene strongly affects a variety of phenotypic traits. While pleiotropies do exist - a famous example causes phenylketonuria in humans - the study shows that they are not common in a broad sample of gene mutations, as creationists claimed. As a consequence, even complex organisms can adapt through mutation without paying a price for their complexity.

From the abstract:

As perceived by Darwin, evolutionary adaptation by the processes of mutation and selection is difficult to understand for complex features that are the product of numerous traits acting in concert, for example the eye or the apparatus of flight. Typically, mutations simultaneously affect multiple phenotypic characters. This phenomenon is known as pleiotropy…. Some authors have suggested that pleiotropy can impede evolutionary progress (a so-called ‘cost of complexity’)…. Here we show, by studying pleiotropy in mice with the use of quantitative trait loci (QTLs) affecting skeletal characters, that most QTLs affect a relatively small subset of traits and that a substitution at a QTL has an effect on each trait that increases with the total number of traits affected. This suggests that evolution of higher organisms does not suffer a ‘cost of complexity’ because most mutations affect few traits and the size of the effects does not decrease with pleiotropy.

Wired has a nice article about the paper including some quotes from the PI:

“I think the main broader impact of this work is on the evolution-creationism debate,” wrote [Yale University evolutionary biologist Gunter] 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.”

This paper undermines the whole creationist argument based on information theory that has become so popular in recent years. This should be remembered, and pointed out when creationists trot out their silly claims.

Tags: cost of complexity, creationism, DNA, evolution, mutation, pleiotropy

This entry was posted on Saturday, March 29th, 2008 at 4:15 am and is filed under evolution, religious extremism. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.