The Plausibility of Life

September 5, 2005
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.

September 15, 2005
Darwin's theory of evolution by natural selection has itself evolved to encompass various complementary theories in a "grand synthesis" of thought, which remains, however, incomplete. Typically, random mutation is regarded as the engine of variation. Kirschner (systems biology, Harvard Medical Sch.) and Gerhart (molecular biology, Univ. of California) borrow from advances in molecular biology to propose a model of "facilitated variation," wherein durable core processes subsume a range of possible physiological responses that enable an organism to adapt to changing environmental conditions. Further, they argue, many genetic functions can be characterized as "exploratory," i.e., permitting adaptations to circumstances. In standard evolutionary thought, this might remind some of Jean-Baptiste Lamarck's theory that acquired traits can be passed on to later generations. Not so, the authors contend, for these variations are inherent to the organism. By using analogies and sequentially developing key points, they skillfully lay out their arguments so that, while drawing on current research, their work is remarkably comprehensible to general readers. Is facilitated variation a final theory of evolution? Kirschner and Gerhart persuasively deal with anticipated objections and suggest a course for future research as well as examine the theory's broader social implications if it is proven correct. For larger public and all academic libraries. -Gregg Sapp, Science Lib., SUNY at Albany

Copyright 2005 Library Journal, LLC Used with permission.

Starred review from September 15, 2005
Since its publication a century and a half ago, Darwin's revolutionary theory of evolution has explained very well how natural selection winnows out the mutations most helpful in fitting a species to survive. Now two neo-Darwinian biologists have boldly extended the original paradigm by showing how the deep molecular biology of the cell actually fosters biological novelties when plants and animals need them most, not merely when random chance generates them. Surveying the latest genetic research, Kirschner and Gerhart adduce evidence that nature has preserved and compartmentalized those core innovations that maximize the adaptive flexibility of species from yeasts to humans. The dynamics of protein chemistry and the plasticity of embryonic cells combine to make creatures capable of assuming many different forms in a wide range of environments. The deepest and most stable processes in biology, thus, are those that prime species for further evolution. It is this biological priming for evolutionary change that Darwin's great rival Larmark was groping toward when he stumbled into error. And it is a theoretical realignment that acknowledges this "facilitated variation" that Darwin's disciples now need in order to fend off skeptics who have latched onto the implausibility of the old scientific orthodoxy premised on entirely random and gradual change in species. Remarkably lucid and comprehensive, this new theoretical synthesis will thus shift the grounds for debate in the controversy surrounding organic evolution.(Reprinted with permission of Booklist, copyright 2005, American Library Association.)