The evidence for evolution is over-whelming, yet a substantial proportion of Americans (and people of other nationalities) have doubts about the reality of evolution. These doubts tend to come in two related flavors: Darwin's theory of evolution is, after all, “only a theory”; and creationism (and its close relatives, such as “intelligent design”) represents a plausible scientific alternative to evolution. Despite a long history of legal rejections of these notions, including the Kitzmiller v. Dover decision in 2005, this distrust and misunderstanding of evolution remains pervasive. When your seatmate on an airplane or your uncle Ernie at the dinner table asks what you, as a biologist, think this evolution stuff is all about, how should you respond? Tell them what I would: Read Jerry Coyne's excellent new book, Why Evolution Is True.
Coyne, a distinguished evolutionary geneticist at the University of Chicago and a regular contributor to National Public Radio and The Times Literary Supplement, begins by defining the modern theory of evolution in terms of six components: evolution, gradualism, speciation, common ancestry, natural selection, and nonselective mechanisms. What distinguishes Coyne's treatment from many previous books on the topic is a determined focus on prediction and retrodiction: “If evolution is true, then we predict that.…” Throughout the book, Coyne uses this simple but powerful device to illustrate how scientists have accumulated the evidence demonstrating how and why evolution happened and continues to happen.
This approach is particularly successful in discussions of the evidence for evolution, gradualism, and common ancestry in the first half of the book. In lucid prose, Coyne leads the reader through the logic of how evolution makes specific predictions about the fossil record and the structural, developmental, and genetic characteristics of organisms. Many of the examples here—the evolutionary transitions of amphibians, birds, and whales—are well known but engagingly presented. The discussion of vestigial structures and pseudogenes is particularly compelling, clearly conveying how such features can make sense only in the light of evolution.
My favorite chapter was “The Geography of Life.” As in several other chapters, Coyne begins with a brief historical anecdote—here the real-life Robinson Crusoe (Alexander Selkirk) and the fellow (nonhuman) inhabitants of his remote island—to explore evolutionary predictions about why organisms occur where they do. Coyne's diverse examples, drawn largely from terrestrial vertebrates and plants, interweave the themes of dispersal, contingency, and convergent evolution in explaining biogeographical patterns at both large and small scales.
The middle sections of the book focus on the mechanisms of evolution and diversification. Coyne clearly lays out the logic of natural and sexual selection and explains how these can lead to simple and complex adaptations. This provides a good summary of the abundant evidence we have for selection and adaptation, but the narrative flow of the material is sometimes clogged by the sheer number of examples—finches and field mice, test-tube evolution and antibiotic resistance, dogs and mustards. The discussion of speciation is masterful but a little pedantic—I kept wishing for jazzier biological examples here.
But Coyne returns to top form in his presentation of human evolution. Historical anecdotes, the abundant hominid fossil record, recent genetic and genomic analyses, and a little comic opera are combined to create a dynamic evolutionary history of us. It is hard for me to imagine an open-minded reader who will not be engaged and convinced by this presentation—evolution happened.
Coyne ends the book with a brief discussion of the extra-scientific dimensions of our challenge: Many people will not be convinced by logic and evidence alone, if they perceive “belief” in evolution as incompatible with their moral or spiritual beliefs. This discussion thoughtfully distinguishes between the evidence for evolution—and the high standards needed for such evidence—and the broader implications of evolution for human behavior, morals, and spirituality. Why Evolution Is True is a thorough and compelling introduction to the logic and evidence for evolution, for every monkey's uncle.