Mutation: Increasing, Decreasing, or Just Changing of Function?

Can random mutations (changes in the genetic material) lead to changes in organisms that render them more “fit” for their environments? How would one determine whether a particular adaptation could be “considered a gain, loss or modification of function” at the cellular level?

According to a review by Michael Behe, PhD, professor of biochemistry at Lehigh University, where he analyzes changes in microorganisms, most of the changes that occur as a result of mutation cause a loss of, or change in, a molecular function and do not add to the genetic information content. For example, Dr. Behe, who believes that the life evolved from a common ancestor, points out that evolutionary history shows that cavefish have lost their ability to see and snakes have lost their legs–and also that these physical (phenotypic) changes are based in molecular changes (alterations in DNA leading to changes in expression of that information).

Then, Dr. Behe points out that, although the overall effect of a mutation may be adaptive, the mechanism whereby the change in function occurs can only be as a result of three types of mutations:

1. a mutation “that produces a specific, new, functional coded element,”
2. a mutation that results in “loss of function of a specific, pre-existing, coded element,”
3. a mutation that does not lead to loss or gain of a functional coded element, but just changes it slightly, for example, changing the strength of a signal.

Makes sense; a typo that changes a story can only make it better, worse or different. Although the microbiological data suggest that the first scenario can and does occur, it is important to realize that the vast majority of mutations fall within the latter two categories–possibly providing a serious challenge to some aspects of the accepted mechanism for evolution.

Interestingly, Dr. Tim Cooper of the University of Houston and Christopher Marx of Harvard, recently published results that add to this story. They found that, even when a beneficial mutation occurs, numerous “beneficial” mutations tend to decrease evolutionary fitness. Does this mean microevolution, or even macroevolution, does not happen? No, as for micro, the researchers found that their bacteria increased in “fitness” by 35%. As for macro, it is debatable whether the results apply. But it does suggest that “random mutations followed by natural selection,” as a mechanism which is thought to drive evolution, needs to be reevaluated.