I’ve finally gotten around to reading atheist biologist Jerry Coyne’s book, Why Evolution is True (Viking, 2009), and if you follow this blog, you know that, as a religion-friendly agnostic, I’m not always sympatico with Coyne’s most strident and obnoxious atheist postings at his blog site. So you might be curious to know if I’m equally resistant to Coyne’s book. Well, here’s my response. Ready?
I like it!
But I’ll start off by saying something that I wasn’t thrilled with about the book. The Introduction is a tired rehearsal of the contemporary public evolution wars’ state of play. (Here’s the short version: various lay constituencies—most obviously American fundamentalists—are bewilderingly ignorant of science.) Likewise, chapter 1, in which Coyne defines and clarifies what evolution actually is, can be skipped without harm (assuming you have an intellectual pulse). The Introduction and the 1st chapter function as primers for those who, for whatever reason, haven’t really been paying attention at all.
But it’s in chapter two, when Coyne actually starts laying out the case for evolution, that the book shines. Chapters 2-4 set out the converging lines of evidence for evolution clearly and briskly, beginning with the fossil record (chapter 2), followed by vestigial clues, embryology, and bad design (all in chapter 3), and concluding with evolutionary bio-geography (chapter 4). This is Jerry Coyne as Colombo, laying out the “crime scene” for spectators and piecing the evidentiary puzzle together, building a compelling picture from the converging lines of evidence. Any reasonable and unbiased person, reading just chapters 2-4, ought to be able to say of life’s diversity, “Evolution did it.” Granted (as at any crime scene) there are pieces of the puzzle that are missing, but Coyne lays out admirably the puzzle pieces that we do have, and they bring us to a reasonable conclusion (the Earth is old and plants and animals have changed over time). Nebuchadnezzar, the writing is on the wall. And if chapters 2-4 don’t quite convince you, chapters 6-8 should seal the deal (in which sexual selection, speciation, and the origin of humans are well discussed).
But the fact that evolution has occurred is, in a sense, the easy part, because it’s pretty darn obvious when you stop and take a look. Even an Intelligent Design proponent like biologist Michael Behe doesn’t deny the basic outlines of life’s antique history and radiation from a common ancestor.
So for reasonable people, the question of evolution is really not so much concerning its occurence, but whether the basic mechanisms of evolution are sufficient to account, all by themselves—and without any guiding telos (design, end, purpose)—for the astonishing diversity and complexity that we actually do see. And there’s the rub, for this is where all the toxic energies between atheism, agnosticism, and theism gather into the oil pan of ultimate meaning: are the mechanisms of evolution unguided and contingent? Did life—and by extension, humans—emerge on Earth by blind forces, or are we here for some purpose? And this is where we come to what I regard as the most important (and interesting) chapter in Coyne’s book: chapter 5 (which Coyne titles “The Engine of Evolution”). This chapter, smack dab in the middle of the book, is pivotal because it’s at this point that we discover whether Coyne is able to muster a concise and robust defense of unguided natural selection as the chief engine for replacing God as the source for life as we find it. As Coyne puts it (115):
It is no surprise that early naturalists believed that animals were the product of celestial design, created by God to do their jobs.
Darwin dispelled this notion in the Origin.
Coyne’s curt posturing aside, does he, in chapter 5, reach his target? That is, does he make a compelling case for natural selection’s power? Here, I have to say that Coyne disappoints a bit. He makes a reasonable case, but not a wholly compelling one. In other words, I think that Coyne leaves room for a “God of the gaps.” To use the game of chess as a metaphor, in chapters 2-4 and 6-8 Coyne definitely achieves check on the telos crowd, but in chapter 5, where Coyne might have finished the game, he simply does not reach checkmate. It makes you wonder why. If natural selection is so compelling a mechanism for accounting for life’s astonishing complexity and diversity, why doesn’t Coyne make a stronger case for it?
I think that Coyne doesn’t make a stronger case precisely because the mechanism of natural selection is, indeed, the weakest link in the chain of the evolution thesis. Coyne’s qualifying language in the chapter seems to concede as much. He speaks, for example, of the impossibility of witnessing macroevolution in plants and animals (page 133), and therefore of the necessity for biologists to at least generate “plausible” scenarios for the emergence of new traits (see page 120). With regard to accounting for complexity by natural selection, Coyne endorses the use of the term “feasible” as an adequate bar for scientific explanation to cross (page 138). But a less charitable term for “plausible” and “feasible” explanations, absent evidence, is “just-so stories.” And Coyne, toward the end of his book, deploys just such a critique against evolutionary arguments that he does not like (page 228):
There is an increasing (and disturbing) tendency of psychologists, biologists, and philosophers to Darwinize every aspect of human behavior, turning its study into a scientific parlor game. But imaginative reconstructions of how things might have evolved are not science; they are stories. Stephen Jay Gould satirized them as “Just-So Stories,” after Kipling’s eponymous book that gave delightful but fanciful explanations for various traits of animals (“How the Leopard Got His Spots,” and so on).
It is also in chapter 5 that Coyne, uncharacteristic of the rest of the book, briefly drops his appeals to positive evidence for evolution and instead devotes a couple of pages to hectoring ID for its inadequacy. Put, as it is, right in the middle of his chapter on the positive case for natural selection, it comes across (ironically) as blue pipe smoke blown into the room for the purpose of clouding the judgment concerning natural selection’s efficacy. He also indulges in some special pleading (as on page 136):
What’s the alternative theory? We know of no other natural process that can build a complex adaptation.
It is here, at this part in his book, that Coyne displays a hint of impatience and frustration (and sounds more like the Coyne of his blog). Natural selection is “plausible” and “feasible” enough for Coyne, and if it’s not enough for you, what’s your alternative? Put up or shut up. And here’s how Coyne concludes the fifth chapter:
So where are we? We know that a process very like natural selection—animal and plant breeding—has taken the genetic variation present in wild species and from it created huge ‘evolutionary’ transformations. We know that these transformations can be much larger, and faster, than real evolutionary change that took place in the past. We’ve seen that selection operates in the laboratory, in microorganisms that cause disease, and in the wild. We know of no adaptations that absolutely could not have been molded by natural selection, and in many cases we can plausibly infer how selection did mold them. And mathematical models show that natural selection can produce complex features easily and quickly. The obvious conclusion: we can provisionally assume that natural selection is the cause of all adaptive evolution—though not of every feature of evolution, since genetic drift can also play a role.
True, breeders haven’t turned a cat into a dog, and laboratory studies haven’t turned a bacterium into an amoeba (although, as we’ve seen, new bacterial species have arisen in the lab). But it is foolish to think that these are serious objections to natural selection. Big transformations take time—huge spans of it. To really see the power of selection, we must extrapolate the small changes that selection creates in our lifetime over the millions of years that it has really had to work in nature. We can’t see the Grand Canyon getting deeper, either, but gazing into that great abyss, with the Colorado River carving away insensibly below, you learn the most important lesson of Darwinism: weak forces operating over long periods of time create large and dramatic change.
No doubt this is true, and a good story. But is it the whole story? Why, for example, doesn’t Coyne illustrate the power of the idea of incremental natural selection in an intellectual take-down of punctuated equilibrium, or the theses of Jerry Fodor, or by putting forth plausible or feasible explanations for the Cambrian explosion and the human mind? And how about the beginnings of life itself? Or refuting the ideas of Simon Conway Morris? You won’t find much of anything, not even in passing, on any of these subjects in Coyne’s book. Perhaps he felt (reasonably) that these might take him too far afield and make the book too long. Perhaps he didn’t want to lose focus. But by not dealing with them he really has failed to hit up against the hardest questions that the title of his book would seem to be in need of addressing if, indeed, we are to know why undirected evolution is true.
Coyne’s book is good, but checkmate it is not.