I recently picked up a copy of Jerry Coyne’s new book, Why Evolution is True. You can also visit Jerry Coyne’s blog of the same
name, Why Evolution is True. This book review is being written as I make my way through the book – the first thing I need to point out is that I am a biologist, and like the vast majority of biologists I happen to consider that evolution is indeed true. That being said, I’m also a little dismayed by the outpourings of religiously motivated twaddle-merchants who seek to place creationism on an equal footing. It is these kind of anti-science arguments that the book is aimed at.
Coyne sets the scene in the preface: the ruling in the 2005 Harrisburg trial (Kitzmiller vs Dover Area School District). This was a resounding defeat for a group attempting to manoeuvre creationism into the science curriculum. Despite this, similar shenanigans keeop cropping up across the USA. And indeed, at least one UK state-funded school has gone down the same route (The Guardian – Top school’s creationists preach value of biblical story over evolution). The brief introduction continues the theme of religious belief versus acceptance of evolutionary theory.
The first chapter proper is entitled “What is Evolution?”, and presents six “parts” or concepts that are important to evolutionary theory. Firstly, the idea of evolution itself – that over time species undergo genetic change, and that this need not happen at the same rate (examples of horseshoe crabs and the ginkgo are given for slow-changing taxa). The second part is that of gradualism – the notion that evolutionary change is slow, so slow that long periods of time are required. In fact this can be one of the stumbling blocks for many people, for whom the short human lifespan doesn’t necessarily equip them to grasp deep time. The third idea is of speciation – that lineages split to yield new species. As Coyne observes, this is intimately tied to the fourth part, common ancestry, which can be seen at different levels, from molecular to anatomical. The fifth part is the most significant element of Darwin’s theory – natural selection. It does seem to me that this subsumes a number of concepts, including notions of variation and heritability, and so is the major Darwinian innovation here. Finally, the sixth part is that of processes other than natural selection can cause evolutionary change – genetic drift for example.
Chapter one also deals with the issue of the word theory – possibly the most abused weapon of the creationists, who generally take the tack of using colloquial definitions of “theory” to suggest that supporting proof or evidence is lacking – as the book goes on to show, this is so far from the truth that the title of the book is most definitely not mistaken. In fact, despite the study of evolution largely being a historical kind of science, evolutionary theory enables us to make predictions about what we might expect to see in the geological/palaeontological record or in the genomes of different species: these predictions are invariably confirmed.
The second chapter “Written in the Rocks” deals with the palaeontological record of past species. It clarifies issues to do with the so-called “missing links” so beloved of creationists. Documented examples of gradual change found in the fossil record include several invertebrates: transitional series demonstrating the evolution of birds, the evolution of amphibians and the transitions to the terrestrial habit and the evolution of whales are all given as examples where evolutionary theory has enabled scientists to make predictions of what the fossil record would show, predictions fully supported by later discoveries. The ability of evolutionary theory to make testable (and disprovable) predictions is a recurrent theme in the book, and is really a good indicator of its superiority over creationist explanations.
Chapter 3, “Remnants: Vestiges, Embryos, and Bad Design” shows how evolution leaves its mark in occasional atavisms, in patterns of embryonic development and in the “molecular legacy” revealed by the large scale genome sequencing projects. Interestingly, I can recall being taken to task at a conference in around 1989 by Richard Lewontin, Coyne’s PhD supervisor, over our then non-existent plans to sequence the Drosophila melanogaster genome (he was concerned by what would be chosen as the standard “wild type” genome). Now we have the sequence of 12 different Drosophila species (see my post on the polytene chromosomes and genome sequences of the Drosophilids over at Flies & Bikes). It’s also worth looking at my recent article on the Genome Sequence-based Tee of Life).
Biogeography is the subject of the fourth chapter, “The Geography of Life”, which shows how the evidence of both extant and fossil taxa across continents, continental islands and oceanic islands clearly argues against creation, and instead makes a logical fit to evolutionary theory. Patterns of distrbution of animals and plants across the world were something that puzzled Victorian naturalists – ideas of plate tectonics had not been formulated. Clearer perhaps were the explanations of diverse species on recent oceanic islands, such as Hawaii and the Galapagos. The theme of testable predictions is raised again here, with the nice example of Glossopteris, a fossil tree found in the southern hemisphere, and which was predicted would be found in Antarctica. It was, and indeed 30 odd pounds of Glossopteris fossils were carted back by Scott’s ill-fated polar expedition. Chapter 5, “The Engine of Evolution” includes a clear statement of why “Intelligent Design” fails as an explanation of the world around us: “Since ID itself makes no testable scientific claims, but offers only half-baked criticisms of Darwinism, its credibility slowly melts away with each advance in our understanding”. Unfortunately, this is probably untrue of the religiously-blinkered.
Darwin was possibly more troubled by peculiar (and on the face of it inexplicable) structures auch as the peacock’s tail than he was by the mechanisms by which eyes evolved. He did of course invoke sexual selection as a mechanism, and the sixth chapter, “How Sex Drives Evolution” deals with this. And convincingly. I was particularly interested to see mention of an experiment that my colleague Tim Halliday and colleagues conducted using the peacocks at Whipsnade Zoo in Bedfordshire, which demonstrated the sexual selection pressure on peacock tails. Interestingly this settled a matter that had been discussed by both Wallace and Darwin: an experimental demonstration of sexual selection.
The Origin of Species is, perhaps surprisingly, not really covered at length by Darwin in On the Origin of Species – here, Coyne devotes an entire chapter to the subject, and covers the issue well. Good examples are given, which clearly provide evidence of how speciation processes operate, including experimental recapitulation of a polyploidy-related speciation event in plants: that of Welsh groundsel, in which it’s origin as polyploid hybrid of two other species was confirmed by laboratory crosses between those two species in which the hybrid species was synthesised. Human origins are covered in the eighth chapter, “What About Us?”, and the question of whether human races reflect a meaningful biological reality is dealt with.
Why Evolution is True is an excellent little book – it clearly states why the author, and indeed the vast majority of biologists, accept evolutionary theory as true. It takes an excellent strategy of illustarting the deifference between the scientific and colloquial use of the word “theory”. In particular I felt the running theme of how evolutionary theory makes testable predictions makes celar distinctions between this scientific explanation for the diverstiy of life over archaic supernatural explanations was particularly effective. But of course in this reader, Coyne is preaching to someone with a pretty good grasp of the biology. And while I was particularly interested in comparing the material covered in this book with the kind of arguments advanced by the creationist in The Big Question TV programme (see this recent article -The Big Question – The Bible and Evolution), what kind of impact is this going to have on the evolution vs creationism debate? I worry that the creationist side is so undereducated in science, and unlikely to read beyond a cover (witness the recent furore over the dreadful “Darwin was Wrong” New Scientist cover – Darwin was right), and certainly aren’t going to be swayed from their religious “truth”. Still, the book does offer clear arguments against many of the lies and misrepresentations proffered by the creationists. And it’s an enjoyable read.