Why Evolution is True

I wasn't particularly keen on biology at school. But reading Jerry Coyne's excellent Why Evolution is True, has made a convert of me. I suspect that if I'd had a teacher with this much enthusiasm and wit, I'd have changed to the life sciences path in an instant.

Despite the title and Coyne's comments in the preface, which clearly show that it is intended as something of a counter to the current enthusiasm for creationism in certain quarters, the book is admirably positive, arguing for evolution rather than against creationism. For, quite rightly, the burden of scientific proof lies not on evolution but on creationism which, if it is have any scientific credibility, must be able to provide better answers to problems already solved by evolutionary theory, rather than simply pointing to minor difficulties without having anything positive to put in its place. The result, then, of Coyne's efforts is a neat, concise book that provides a comprehensive overview of modern evolutionary synthesis and which provides an excellent overview of much of the scientific evidence in its favour.

The book begins with an initial exploration of the basics of evolutionary theory, together with a series of testable predictions drawn from the theory. These predictions do not concern the future evolutionary paths, but rather involve a series of hypotheses about where particular creatures might be found in the fossil record and where common ancestors might be found. The theory also suggests a series of what Coyne terms retrodictions: features in living creatures that can only be understood in the context of evolution.

The evidence quickly starts to pile up. Fossils are found where the theory predicts, the most primitive at the deepest levels, the more complex towards the top. Missing links are found and mosaic fossils are used to prove the common ancestry of birds and reptiles. Vestigial features show how evolution has progressed, re-tasking some feature to fulfill new functions while leaving others as relics of a distant ancestry. Bad design decisions abound. Nowhere is this clearer than in the tortuousness of embryonic development, with human embryos recapitulating the forms of their evolutionary ancestors before finally assembling themselves into their final forms. The geographical distribution of life, too, can only be understood in terms of evolution. Thus the oceanic islands, which show radiation of limited sets of species and the complete absence of others, only makes sense when thought of as the evolution of a handful of marooned survivors.

Evolution can also be seen happening in real time. The appearance drug resistant bacteria, lab selection experiments, even pet fanciers who artificially enhance particular traits in one breed or another, all of these show selection at work in one form or another. Even apparent maladaptions, such as the male peacock's burdensome tail, can be explained through selection albeit the sexual selection of the finest male tails by picky peahens. Knowing of sexual selection, it becomes possible to make a further prediction: species where males and females show a substantial difference in appearance — sexual diamorphism — the larger or more ornate sex will be the ones who compete for a mate and, further more, species that show sexual diamorphism will generally be non-monogamous. A particularly fine example of this last is the superb fairy wren which, while socially monogamous, is actually sexually promiscuous and features a brightly coloured male and a grey female.

The book concludes with a consideration of human evolution, something Coyne conceeds that a lot of people reject even while accepting the evidence of evolution in non-humans. But the evidence in favour of human evolution is clear. A number of fossils have been recovered showing various branches in the Homininae progressing from a common ancestor into creatures more like modern humans.

So, the fix is in. Evolution can be used to make verifiable predictions about the past history of life on Earth. It can be used to explain the odd distribution patterns of living creatures and to explain how everything the features of great danes and chihuahuas and finches and MRSA. And yet. And yet people still reject it. Coyne puts this down to the assumed belief by some people that, if evolution is true, morality will evaporate and people will choose to live in a Hobbesian war of all against all. But this isn't necessarily the case: evolution is neither moral nor immoral, it simply is. And it is a mistake to assume that there is something ineluctable about our genetic heritage, something that compels us to behave in a particular way regardless of our environment.

I don't think I've learnt quite so much from a book for a very long time. As an introduction to a truly fascinating area of biology, wonderfully well written, consistently exciting and packed to bursting with fascinating facts, I can't recommend this highly enough.