Why evolution is true

Janet Smith uncovers many hidden gems in the dig for evidence to support Darwin's theories

April 2, 2009

Jerry Coyne has a take-no-prisoners approach to purveying his Darwinian message, which he does with skill, knowledge and mostly good writing but with not a little pinch of evangelism and reiteration. Like the UK's Richard Dawkins, whom he cites, he does not suffer followers of creationism gladly. Nor does he like its refurbished modern counterpart (or "descendant", as Coyne gleefully puts it), intelligent design; and in this last respect I agree with him.

Coyne deals very effectively with intelligent design in the preface, where he explains a widely reported recent US court case, Kitzmiller et al v Dover Area School District et al, in which a school administrator's ruling that intelligent design should be taught alongside Darwin's theory of evolution was challenged and overturned. He quotes extensively from the judge's decision, which was that "intelligent design is an interesting theological argument but it is not a science". In the context of US law, where the teaching of religion is not allowed in state schools, this was sufficient to overturn the administrator's ruling. Coyne quotes the judge further: "The fact that a scientific theory cannot yet render an explanation on every point should not be used as a pretext to thrust an untestable alternative hypothesis grounded in religion into the science classroom to misrepresent well-established scientific propositions."

This is good and sound advice, so why doesn't Coyne take it? Instead, in his introductory chapter he sets the stage for an entrenched and doom-laden conflict: "What is at stake is nothing less than science itself and all the benefits it offers to society." This certainly seems to justify the statement on the dust jacket that: "This is a book that should not be necessary, and yet it has never been needed more." But is it true? The origins of the "dispute" between Darwinists and creationists goes back to the time of Darwin, when "99 per cent of scientists were creationists"; this is no longer the case.

The tone of the book is surprisingly defensive. After dismissing intelligent design as an unsupported form of creationism that should not, and cannot, be taught alongside Darwin's theory of evolution (or indeed any part of science), Coyne then keeps on coming back to it. He peppers his book with little snipes and asides showing how intelligent design cannot explain this or that, interspersed with frequent assertions that "evolution is true". To my mind, this is unnecessary and detracts from the seriousness of his main point, which is that the evidence and sheer volume of Darwin's work and all the science that has followed it unequivocally support Darwin's theory of evolution.

There is much to admire and ponder over in this book and there are some great quotes; Coyne is clearly enthused by evolution and he knows quite a lot about it. The fossil record is his favourite subject and the one he pursues in most depth, in chapter two, and with perhaps a little too much detail for the general reader. However, I found it strangely unconvincing. It shouldn't be, since all the best examples are there - transitional forms such as the fish/amphibian descendant Tiktaalik; Archaeopteryx lithographica and the evolution of birds; and the extraordinary "evolutionary dead end" Microraptor gui. There is some fascinating detail here, although perhaps only the hardcore evolutionary biologist (or a developmental biologist such as me) would concur with the statement: "Perhaps the most thrilling find of all is a 530-million-year-old fossil from China called Haikouella lanceolata, resembling a small eel with a frilly dorsal fin." It also had a notochord and a brain, heart and so on - in other words, it is the "first" chordate - the group that gives rise to all vertebrates including ourselves.

The book is uneven, overlong and not always up to date; its structure can get a bit confusing, the titles don't always match, and Coyne is clearly happier talking about fossils than about genes and development. This is a pity, because there is now a vast array of genetic and developmental data that supports the theory of evolution, much of which is barely touched on in this book. Most notably, he omits much of modern "evo-devo" (evolution-development) and does not mention Hox genes, one of the most powerful arguments for a common ancestry of vertebrates.

Nevertheless, there are many hidden gems in this book, and running through it is the undercurrent of Darwin's influence and relevance to modern science. This comes out clearly in the sections on biogeography and, perhaps the most astonishing of Darwin's insights, human evolution. Biogeography makes predictions and solves puzzles, and Darwin's ideas still loom large. No creationist ever tried to refute biogeography, so this chapter is also refreshingly free of reference to intelligent design, and all the easier to read for that. More than a century before tectonic plates and continental drift, Darwin and others worked out that the distribution of plants and animals across the globe was consistent with the movement of continents and an earlier supercontinent, Gondwanaland, and predicted fairly accurately much of the subsequently found fossil record (including marsupial fossils in Antarctica and human ancestors in Africa).

Darwin is the star of this book, and he generally puts it better than Coyne. Chapter six is on how "sex drives evolution" and contains my favourite Darwin quote of all. "I remember well when the thought of the eye made me cold all over, but I have got over this stage of complaint and now trifling particulars of structure often make me very uncomfortable. The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!"

This comment is frequently cited by creationists as evidence that Darwin himself had doubts about evolution. Of course he did: he was a scientist and he didn't have all of the evidence we have today. More interesting, though, is that for Darwin to explain the peacock's tail, he came up with an idea far less palatable to Victorian Britain than evolution itself, that of female (sexual) choice. Darwin accepted it, but tellingly Sir Charles Lyell never did.

Why Evolution Is True

By Jerry A. Coyne

Oxford University Press 309pp, £14.99

ISBN 9780199230846

Published 22 January 2009

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