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1 December 2006 Molecular Evolution for the Masses
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The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution. Sean B. Carroll. Norton, New York, 2006. 288 pp., illus. $25.95 (ISBN 0393061639 cloth).

In his new book, Sean Carroll summarizes the molecular evidence for evolution by natural selection for a nonspecialist audience. As stated in the introduction, The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution is intended to marshal the evidence from DNA sequence data to help contribute to the debates on evolution versus creationism/intelligent design. Although there are many books intended to educate the public about evolution (and we certainly seem to need them now), Carroll's book may be the first to focus specifically on the DNA evidence.

At least among biologists, Sean Carroll is an author who needs no introduction. He is one of the most prominent evolutionary developmental biologists alive today, and is a professor of genetics (and Howard Hughes Medical Institute investigator) at the University of Wisconsin, Madison. In addition to his credentials as a scientist, he is also no stranger to writing for general audiences. His first such book, Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom (New York: Norton, 2005), received numerous laudatory reviews from both scientists and the popular media (e.g., USA Today).

Carroll's new book describes adaptation through natural selection at the molecular level. Carroll starts out by explaining the “everyday math of evolution,” how mutation and selection lead to changes in populations over time. He then introduces readers to the basic dogma of molecular genetics and the basic size and composition of genomes among taxa. With the basics of molecular biology and population genetics in hand, Carroll delves into the major themes of the book: the idea of “immortal” genes (genes with essential functions that have been preserved by natural selection for billions of years), “fossil” genes (functionless pseudogenes that accumulate many mutations), gene duplication and divergence as a means of developing new functions, the parallel acquisition of similar functions in different lineages, and the importance of “tool kit” genes for making complex structures. Many examples are derived from the evolution of the opsin genes and their relationship to the evolution (and loss) of color vision in primates and other vertebrates. There is also a chapter on molecular evolution and human diseases (e.g., sickle-cell anemia and malaria).

The last two chapters are somewhat out of step with the rest of the book, in that they have little to do with molecular evolution per se. One chapter focuses on why and how so many people resist evolutionary biology (using Lysenko's campaign against genetics as one example and the bizarre resistance of many chiropractors to immunizing patients against diseases as another). The final chapter discusses inadvertent selection by humans on natural populations of animals (e.g., body sizes in commercially exploited fish species).

Carroll takes considerable care to try and explain everything clearly and with everyday language. Rather than diving right into molecular evolution at the beginning of a chapter, he starts each one with a personal or historical anecdote. Furthermore, the book is extensively illustrated, with a black-and-white photograph or diagram appearing every few pages.

Overall, I enjoyed reading The Making of the Fittest, and I learned quite a lot from it. My research specialty is not molecular adaptation, and so many of the examples were new and exciting to me. But despite the fact that I found this book enjoyable and enlightening, I am uncertain as to how much it will contribute to the continuing battle between creationists and evolutionists. First, I question to what extent this book describes, as the subtitle proclaims, “the ultimate forensic record of evolution.” The book primarily focuses on the molecular signatures of natural selection. But I think the main issue in the current “evolution wars” is not the causes of change in allele frequencies within populations. Instead, the main issue is whether the diverse species we see today have been independently created by supernatural forces or whether they originated from other species through evolution. When I think of “DNA and the ultimate forensic record of evolution,” I think of phylogenies based on DNA sequence data, which show that all species are related to other species and are not independently created (or, if species were independently created, why should so many of their genes show concordant, nonrandom, hierarchical patterns of similarity and descent that link them to all other species alive today?). Phylogenies are certainly mentioned in Carroll's book, but not really as evidence for evolution versus special creation of species. In a similar vein, despite the extensive discussion of The Origin of Species, the book contains little or no mention of the origin of species. Of course, this is a failing in Darwin's book also, but one that Carroll need not replicate. To my recollection, speciation is barely mentioned in The Making of the Fittest, and is certainly never discussed.

Second, because the book is focused at the molecular level, some of the examples are not that easy to wrap one's mind around. For example, the book is full of wonderful examples of evolutionary patterns in opsin genes. But I would hesitate to use these examples in many cases, just because it would take so long to explain to students and nonscientists how opsins work and why the molecular variation matters. Similarly, for some of the traits discussed, natural selection seems to have been documented primarily at the molecular level. Thus the links between molecular variation, phenotype, and individual fitness in natural populations are sometimes assumed rather than thoroughly documented. Because of these issues, I think that many of the examples Carroll describes may have a difficult time competing in the classroom (and living room) with more obvious and intuitive examples, like the coloration of moths or the beaks of Galápagos finches.

In the end, Carroll's new book is a valuable addition to the popular literature on evolution, but it's no Beak of the Finch. On the other hand, being in the same ballpark as Jonathan Weiner's Pulitzer Prize–winning bestseller is really not too shabby.

JOHN J. WIENS "Molecular Evolution for the Masses," BioScience 56(12), 1014-1015, (1 December 2006).[1014:MEFTM]2.0.CO;2
Published: 1 December 2006

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