Truth or Consequences? Engaging the “Truth” of Evolution

John is the only one of the four evangelists who recounts Jesus’ (possibly apocryphal) statement to Pilate that he was in fact a king whose role was “to bear witness to the truth; and all who are on the side of truth listen to my voice.” Pilate is said to have replied to this, “What is truth?” This is a question that Jerry Coyne never really engages in his excellent new book [1], which purports to explain why evolution is “true.” This raises the question of who his intended audience is. But we’ll get there in a minute. First, make no mistake: this is a wonderful book, as far as the explanation of many of the interesting lines of evidence and case histories for evolution go. Coyne is a professor at the University of Chicago who specializes in the genetics of speciation (his previous book on the subject, with H. Allen Orr, is widely recognized [2]). He explains the evidence for evolution not just in terms of speciation, however. He revisits many of Darwin’s arguments, such as the progression of fossils, the importance of vestigial organs, how evolution explains biogeographic patterns, and sexual selection. But he is also able to go far beyond the evidence available to Darwin, with topics such as genetic and molecular support for species divergence, and the record of human evolution. Coyne hits all the right notes, without over-dazzling the general reader with too many molecular complexities or obscure examples. This is a very readable, companionable work that takes its place alongside other fine recent explanations of evolution such as Evolution: What the Fossils Say and Why It Matters, by Donald R. Prothero [3], and Your Inner Fish, by Neil Shubin [4], as well as a great many Web sites that explain the evidence for evolution. It would be an excellent text for a freshman or non-majors course in evolution, or for a local book group. It is a real shame, ironically, that this kind of book has to be produced at all, because it is so perfect a textbook for people needing to know the basic evidence for evolution. Why don’t textbook publishers just produce stuff like this for classrooms? But therein lies a different tale. Unusually for a specialist in population genetics, Coyne has a strong grasp of the highlights of the fossil record, and he focuses on some of the major cases such as the origin of tetrapods (mistakenly called the “fishamphibian” transition), the origin of birds, and the return of whales to the water. So it is a bit surprising that there is not more in his book on the methods we use to study these major features of evolution, notably the importance of constructing phylogenetic trees (which show patterns of lineage branching) to test hypotheses about macroevolutionary processes, or (even more surprisingly) the advent of evolutionary developmental biology. These and other approaches have been tremendously important in the integration of fossil evidence in recent decades. Most importantly, they explain to the uninitiated not just what we regard as the evidence but how we come to see it as evidence. But Coyne is concentrating less on methods and philosophy than he is on the evidence itself—which he reasonably thinks should be enough to convince sentient people of the truth of evolution. The problem is that, as Pilate implied, truth is a personal thing. This is not to say that all morality is subjective and all ethics conditional, and we don’t need to rehash philosophy here. But it seems important in a book entitled Why Evolution Is True to engage the question of truth—and whose truth—at least a bit. Everyone is aware of the level of ignorance and lack of acceptance of evolution among the American populace. The numbers can reach close to 50%, depending on how the questions are phrased, and this statistic constantly appalls many foreign scholars. As my colleague Eugenie Scott at the National Center for Science Education is fond of saying, this is not a problem that you can solve merely by throwing more science at it. The reason is that people don’t always decide what stories they want to believe—how they construct their worldview—on the same basis. Scientists are rationalists, believers in the power of reason, of observation of the natural world, the formation of patterns, the testing of inferences. I said “believers” deliberately. Do we “believe” in the results of our investigations? We shouldn’t; we should accept them provisionally pending further testing.