The Plausibility of Life: Resolving Darwin's Dilemma

We all know Darwin's theory of evolution—natural selection favors some adaptations over others. But where do new adaptations come from? This problem baffled Darwin and is the main point of attack for opponents of evolution. Kirschner and Gerhart, professor at Harvard and UC-Berkeley, respectively, present their solution to the problem and take a few timely shots at the advocates of intelligent design. The key to understanding the development of complex structures, they say, is seeing that body parts as seemingly different as eyes and elbows are formed from the same basic molecular mechanisms. Thus, the authors propose, the metabolic building blocks of life functions can be rearranged and linked in novel ways with less chance of fatal variations than random mutation of DNA would allow. One piece of evidence they offer is the frequency of periods of "deep conservation" following evolutionary anatomical changes, where conventional theory would argue for continuous mutation and change. Though this seems like an elegantly simple solution, the underlying molecular biology is quite complicated. As for proponents of intelligent design, the authors say their theory turns some of their arguments on their head, converting "some of their favorite claims"—such as "irreducible complexity"—into arguments for evolution. (Oct. 19)