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Reviews

Why Evolution Is True

Denis Alexander

Jerry Coyne
Oxford University Press, 336pp, ISBN ­­9780199230846

coyne.jpgPity about the title, but in the flurry of books that have marked the Darwin double anniversary, this is surely one of the best to explain the evidence for evolution for the non-specialist reader. Coyne covers all the main topics of interest: dating, the fossil record, vestiges, geographical distribution of species, evolutionary mechanisms, how sex drives evolution, speciation and human evolution. Along the way some myths are laid to rest, for example that in evolution 'everything happens by chance'. As Coyne states firmly: 'No evolutionist - and certainly not Darwin - ever argued that natural selection is based on chance'.

The book is full of little biological gems that keep one entertained and provide useful tit-bits for that pause in conversation at the next party. Did you know, for example, about the Asian giant hornet, as big as your thumb and the world's largest? It can fly at 25 mph, faster than you can run, and kills several dozen people every year. A group of 20 or so hornets can readily massacre 30,000 honey bees, biting off their heads at a rate of 40 per minute. But in a stunning example of evolutionary adaptation, other bees have found a cunning way to fight back. When the first hornet arrives at their nest, they deliberately lure it inside where it is mobbed and covered by a tight ball of bees. Vibrating their abdomens, the bees raise the temperature inside the ball to 47ºC. Bees can survive this temperature, but the hornet cannot, and is cooked to death within 20 minutes. Touche! As the author points out, biology does not really provide a good basis for establishing moral values.

Just occasionally the author's own worldview breaks through into the science, though in a much less obtrusive way than in some other writers on evolution. 'In a single chapter' of The Origin of Species, Coyne assures us, Darwin 'completely replaced centuries of certainty about divine design with the notion of a mindless mechanistic process - natural selection - that could accomplish the same result'. Well, not really. Darwin himself didn't think in terms of 'mindless mechanistic processes' but he did realise that his book was a direct challenge to the idea of the fixity of species. It is curious how scientists writing about evolution so often use the term 'mindless' when they don't use that adjective to refer to other well-known processes like  quantum mechanics, the origins of the periodic table of elements or the movements of tectonic plates. Only those attached to certain monistic religions or New Age ways of thinking might be tempted to think of material objects or processes as 'mindful', certainly not those creationists whom Coyne refers to disparagingly at regular intervals through the text.

It is fascinating that those biologists who reject any notion of ultimate direction or purpose in the overall evolutionary process, nevertheless find it very hard to weed the language of progress out of their discourse on human evolution Coyne is no exception, remarking that, 'Like all species, we are not an endproduct of evolution, but a work in progress, though our own genetic  progress may be slow'. As it happens most biologists disagree with Coyne, arguing on purely scientific grounds that any further significant human evolution is unlikely. Darwin himself was a temperate progressionist, less ardent by far than some of his contemporaries (such as Herbert Spencer), but it is interesting to see the language of progression still embedded in evolutionary discourse, like a vestige of the creation of the theory itself, reflecting a worldview no longer inhabited by writers such as Coyne.
In his final chapter the author does a good job, on the whole, in mapping out the limits of evolutionary explanations, remarking that questions of ultimate purpose are 'outside the domain of science', and criticising those who seek speculative Darwinian explanations for every aspect of human behaviour in the absence of any solid evidence, a particular weakness in the field of evolutionary psychology.

So why the gripe about the title? The 'in-your-face' claim that evolution 'is TRUE!' seems to reflect the author's own muddle about the distinction between 'facts' and 'theories'. If only the author had read just a little philosophy of science before writing his book. So we are assured that 'there is one moment when a scientific theory suddenly becomes a scientific fact' and near the end of the book the author hopes that we are now convinced that 'evolution is far more than a scientific theory: it is a scientific fact'. Not so. Facts are the primary data that a scientist would need to be hallucinating not to claim as being worthy of general assent. All facts are indeed 'theory-laden', they are not 'naked facts', but they are not the same thing as theories. Theories are like conceptual maps which join up facts and render them coherent. It was Darwin's brilliance to take a huge number of facts and weave them into a convincing theory that has withstood the test of time since 1859 and continues to make sense of great swathes of new data, not least from genomics, to the present day. Calling a map reliable does not make it a 'fact', it simply means that we find it to be trustworthy in light of the present available data.

Do not let Coyne's minor peccadilloes relating to the philosophy of science put you off buying this book though. The biology is well-informed, accessible to the general reader, well explained, entertaining and convincing.

Denis Alexander