Too many good mutations can actually be bad for a species' evolution

Mutation is one of the big driving forces behind evolution, as it can allow species to quickly gain the genetic tools necessary to survive and adapt. But even the perfect mutation can mean trouble if it can't work with others.

That's the finding of researchers at the University of Houston, who recently concluded a five-year study on a bacterial culture. Over approximately a thousand generations, these bacteria have become far better adapted to their environment, with their overall fitness increasingly by an estimated 35%.

The researchers identified the various mutations that have crept into the bacteria gene pool, and then they tried to figure out which combinations of mutations had the most positive effect. They found that the more mutations got added to the mix, the more they interfered with each other, even when - indeed, especially when - the mutations were all trying to solve the same basic problem.

A bunch of positive mutations could easily become a net negative if they didn't fit well together. Moreover, the researchers found that the effect of any given mutation on the bacteria's fitness would vary wildly depending on what other mutations were present. Lead researcher Tim Cooper explains:

"These results point us toward expecting to see the rate of a population's fitness declining over time even with the continual addition of new beneficial mutations. As we sometimes see in sports, a group of individual stars doesn't necessarily make a great team."

Much as I might quibble with his sports analysis, I'll leave my sabermetric leanings to one side. Cooper went on to explain that a surprising amount of mutations end up being antagonistic with others, and that collectively they can greatly slow down the adaption of an organism. Cooper argues that understanding how all this works will offer essential insights into the evolutionary process, and someday it might even help us direct the evolution of bacteria that we depend on for survival.

Via Science. Image via.