Reviewed by Bob Williams
Why Evolution Is True
by Jerry A. Coyne
2009, ISBN 978-0-670-02053-9, $27.95, 282 pages
Jerry Coyne has written for prestigious publications, but this is his first book. He teaches ecology and evolution at the University of Chicago. He is noted for his study of Drosophila, fruit flies.
This book is a systematic approach to the conflict between evolution and creationism. Since almost no creationist is systematic, Why Evolution Is True will be overkill in most situations, but everything is here for the benefit of the evolutionist. The book has an attractive jacket and an unusually distinguished binding. There are many illustrations. These derive from a variety of sources, but many of them are by Kallopi Monoyios, an illustrator-designer of outstanding ability and taste.
In his preface Coyne gives a quick sketch of the Dover trial. Angry parents brought suit in 2005 against the Dover, Pennsylvania, school board for an attempt to force creationism into the school curriculum. Judge John Jones III found for the plaintiffs and sharply defined the issues in a way that should prevent a recurrence, but – alas – creationists are schoolyard bullies and will return, have returned, with new ways to thrust their beliefs on society. For fundamentalists, evolution demotes the human species from a central position and for some even makes it contingent. Coyne did not design his book to convert fundamentalists; he wrote it for those who want testimony to resolve their doubts or gaps in information. It also serves, of course, as an arsenal with which to combat fundamentalist claims.
His first step is a definition of evolution: “Life on earth evolved gradually beginning with one primitive species – perhaps a self-replicating molecule – that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.” He then analyses each component of his definition.
Carl Linnaeus began to classify plants and animals in the seventeenth century. Other natural scientists took up this part of biological study. The results were remarkably the same from one scientist to another. Darwin made sense of these facts with evolution. Relationships became not just gross similarities, but relationship in the very particular sense of affinities by reason of descent from a common ancestor. Since Darwin’s time, genetics and DNA have expanded the process as a general rule of universal applicability and narrowed it by verifiable particularity. This evidence of relationships denies the possibility of de novo design or individual acts of species creation.
It is natural selection that makes the difference in this as in other regards. Favorable changes will be preserved and the accumulation of many small modifications will produce over a long period of time new species. Such an ordering of life from the bottom up instead of from the top down rests on a multitude of facts and laws that are of universal validity and to whose confirmation the united testimony of every relevant scientific discipline has contributed without contradiction or demurral.
The alternative mechanism to natural selection is genetic drift, a process that rests on the fluctuation in population numbers. The degree to which genetic drift plays a role in evolution and how it is restricted to small populations is a subject of controversy among scientists. Coyne takes the position that its role is minor compared to natural selection and that small populations favor its operation.
Coyne sees a problem in the scientific and the vernacular use of the word theory. In the vernacular ‘theory’ and ‘guess’ are interchangeable but in science theory means the body of laws that govern a set of facts. “[I]t is possible that despite thousands of observations that support Darwinism, new data might show it to be wrong. I think this is unlikely, but scientists, unlike zealots, can’t afford to become arrogant about what they accept as true,”
Although Why Evolution Is True is organized very well, Coyne will present interesting observations that spring only lightly from the topic at hand. For example, he discusses plate tectonics, the shift in the continents, and notes that the continents move at a fixed rate. This provides him with the opportunity to observe that if the young earthers are right (they believe that the earth is no older – usually – than 10,000 years), one could stand on the coast of Spain and see New York.
Coyne classifies evidence for evolution as predictive (if evolution is true, we can expect certain facts to be found in the fossil record or in the wild) or, Coyne’s coinage, retrodictive (if evolution is true, we can expect to encounter facts that only the truth of evolution can explain). These distinctions will be the basis for much of what follows.
He explains that the fossil record is biased. No fossils will form from soft-bodied plants or animals – thus providing little from the earliest times – and marine animals will be more frequent in the record. To find fossils is difficult and if they surface so that they can be found, wind and weather can destroy them. Despite these limitations the fossil record is grandly comprehensive compared to that that existed in Darwin’s time. (A biologist recently suggested a bumper sticker aimed at creationists: “We have the fossils – you lose.”)
Determining the relative ages of the various layers of rock is easy. To determine actual age becomes more difficult and depends on radiometric measurement. Young earthers insist that the rate of decay in the isotopes used in measurement has varied over time, but there is no evidence for this and other methods of time measurement confirm the obvious conclusion that the measurement by means of isotopes is correct. The original rocks of earth are no more, destroyed by the convulsions of the early period, but meteors give us an age for the earth of 4.6 billion years. The oldest existing rocks are 4.3 billion years old.
Some, even strict, creationists allow evolution as a factor in the changes within a ‘kind,’ a term from the Bible and not related to science in any way and not usefully defined. A bird is a ‘kind’ and not subject to derivation from another ‘kind’ despite the evidence that birds derive from dinosaurs. Similarly, man is special in this way. Many sophisticated religions let the birds go, but try to maintain man’s special status. But this is an either-or situation, one that admits no compromise.
In a splendid display of the reliability of evolution Neil Schubin determined where and in what age rocks he should look for the fossil of the animal intermediate between fish and amphibian. The result was the discovery of Tiktaalik roseae (The Fish in You by Neil Schubin).
Creationists question the utility of faculties that are transitional. But there are no transitional faculties so far as the possessors are concerned. When the creationist asks what good is an incomplete eye, the question is obviously wrong. What would the creationist prefer to have, half vision or no vision? Similarly, the development of the wing is a puzzle for them although the assistance of wings in birds that do not fly or the benefit of extended membranes among animals that glide should be sufficient answer.
The testimony of the fossil record is unequivocal. It shows the changes that produce speciation and the links between old and new; everything is in the sequence that evolutionary science predicts; and every change is a modification from existing forms. These are not effects that creation ex novo would produce.
The genome – the sum of all the sequences found in the DNA of a species – provides an explanation for all sorts of anomalies that would be inexplicable if evolution were not true. By the comparative study of genomes it is possible to establish relationships and to note how some genes in the DNA have been turned off. Where a close relation exists the genes have been turned off in the same way. Where the same gene has been turned off in species not closely related, the method of the turn off differs. In addition to this there are vestigial characteristics – like the human appendix – that no longer have a function but still survive because elimination would cost too much. This principle of economy plays a major role in evolution.
Intelligent design is a fantasy. Coyne discusses the imperfections – many of which he noted as vestiges or anomalies – and summarizes them in these words: “What I mean by ‘bad design’ is the notion that if an organism were built from scratch by a designer – one who used the biological building blocks of nerves, muscles, bone, and so on – they would not have such imperfections. Perfect design would truly be the sign of a skilled and intelligent designer. IMPERFECT design is the mark of evolution in fact. It’s precisely what we EXPECT from evolution. We’ve learned that evolution doesn’t start from scratch. New parts evolve from old ones, and have to work well with the parts that have already evolved. Because of this, we should expect compromises: some features that work pretty well, but not as well as they might, or some features – like the kiwi wing – that don’t work at all, but are evolutionary leftovers.”
Biogeography is a recent scientific discipline, but an important one. Observation of flora and fauna distribution reveals a number of anomalies that can only be explained by the truth of evolution. After a rapid survey of the peculiarities of life on islands and of the differences and similarities of life on continents, Coyne writes this: “The biogeographic evidence of evolution is now so powerful that I have never seen a creationist book, article, or lecture that has tried to refute it. Creationists simply pretend that the evidence doesn’t exist.”
The evidence is clear, cogent, and inescapable. The fossil record can be dated sufficiently to show the distribution of – for the most colorful example – marsupials. It can also track them geographically and determine where they were in terms of the existing land mass. The marsupials trekked from the tip of South America (when South America formed a part of the unified continent Gondwana) to the connected landmass that became Australia. There they became the dominant form of animal life in country that had drifted away from their original home. This is a beautiful example of “We have the fossils – you lose.”
On the oceanic islands – Galapagos, for example – the life forms are those than can migrate from the nearest mainland, barring exceptions based on exceptionally favorable currents. As a consequence there are no mammals (except some bats on some islands: significantly, these are FLYING mammals). Other terrestrial mammals don’t make the trip and neither do amphibians or fresh water fish, all of them bad travelers. Once in place the animals, fewer in species than on the mainland as a result of the winnowing process of the journey, adapt with great plasticity: a single species of bird will evolve adaptively to fill the niches that elsewhere would be filled by different species.
The nature of Nature is at bottom nasty. The change that natural selection fosters is for the benefit of the individual. Changes do not aim at far-flung improvements. There is no altruism involved. Occasional apparent benefit to a member of another species proves on examination to be the reciprocity of symbiosis. Evolution combines chance (a mistake in the genetic code introduces a mutation) and law (natural selection will promote a beneficent mutation). The aim, if one may be so anthropomorphic, is that the favored members of the species shall live long enough to reproduce. Indifferent nature cares nothing for the individual. Only the survival of the gene matters.
There is evolution without natural selection but its importance is difficult to assess. Some biologists are more persuaded of its importance than others. In a rapid and very uncomprehensive description, genetic drift is mutational modification that has no importance but introduces changes and is found more easily in small populations. Some biologists exclude the necessity of its application to only small populations. The consensus is that its role is minor or difficult to examine. After all, mutations play out often over vast periods of time and the changes introduced by genetic drift may ultimately prove to be more nearly allied than we can discern to those changes subject to natural selection.
Creationists reject evolution for basically religious reasons, but they have many evasions to offer. One of them is the failure of evolution to work its wonders in a way that they can immediately perceive. This is like asking for an over-night Grand Canyon, but there are examples available of evolutionary change taking place relatively quickly. A recent drought on the Galapagos changed the feeding habits of the finches in such a way that beak growth among one group became quickly apparent. Further evolutionary changes have been noted in E. coli strains that generate new generations in a matter of minutes.
The creationist argument from complexity – the argument from gaps, to give it its alternative description – denies the ability of evolution to make the more intricate of nature’s devices. The idea here is that intricate parts in a complex organism cannot evolve, but rely on divine intervention. This is the equivalent of a confession of ignorance, but it has no relevance in the real world.
Some things we do not, may never, know, but other problems disclose – to the discomfiture of creationists – their answers every day. Coyne offers this common sense observation: “If the history of science teaches us anything, it is that what conquers our ignorance is research, not giving up and attributing our ignorance to the miraculous work of a creator.”
In his discussion of sex – an invention made 1.2 billion years ago – the reader may wonder where he is going. The matter, though interesting, doesn’t seem especially pertinent, but, as Coyne shows, even here creationists have missed the point and created (sorry about the pun? Not really) their own characteristically silly position. It is not the whim of some creator as they say, but an outcome of natural selection based on the nature of sexual differences.
On the origin of species Coyne produces a convincing narrative. Darwin has little to say about the origin of species – despite the title of his great work – but the challenge has been successfully met in the last century and continues today. Since the process of speciation is so slow, it is impossible to witness in real time, but assembly of facts from various stages existing now permit a realistic equivalent, one proved by Coyne’s concepts of predictive and retrodictive analysis.
For the creationists who must see to believe there is allopolyploid speciation, a process in which two plants from the same environment hybridize and the result – instead of struggling with an uneven number of chromosomes – reproduces a full set from both parents and breeds a new and fertile species. The process takes two generations and is the cause of most speciation in many plants, 70% in Coyne’s estimate and has been a major factor in speciation from the beginning.
In his chapter on the evolution of humanity, Coyne announces in these words a position that will thrill some and chill others: “We are apes descended from other apes, and our closest cousin is the chimpanzee, whose ancestors diverged from our own several million years ago in Africa. These are indisputable facts. And rather than diminishing our humanity, they should produce satisfaction and wonder, for they connect us to all organisms, the living and the dead.”
Since fossils only occur under special circumstances – few of which are met by terrestrial animals – early human remains are scanty. We have sufficient to confirm that Darwin’s guess about African origin although the migration from Africa may have occurred more than once. We have the dots but lack the information we need to connect them. Creationists have met the challenge of the fossils by declaring some of them human and some of them ape. Their ineptitude is underlined by their failure to agree about which are which. One especially confused creationist identified the same fossil as human in one book and as ape in another. Coyne rightly observes that their contortions are hilarious.
The pedant in me cannot resist criticizing Coyne for his misuse of “exception proves the rule.” He uses it in the popular and incorrect sense that there is no rule that does not have an exception, but the ‘probat’ of ‘exceptio probat regulam’ means test, not confirm. Thus the adage means that if a rule has an exception it fails as a rule and one must look further, elsewhere, or otherwise.
Despite his disclaimer that he intends his book as a primer for the uncertain or a weapon for the combatative, he closes his book with an effort to persuade the opposition. Genes are not destiny and evolution tells us where we have been but not what we are or may be. The truth of all this arises naturally from all that has gone before but is not likely to be convincing for those who refuse conviction. For all this, this is a remarkable achievement, brilliantly written, easy to follow. Now that he has begun to write books, it is a pleasant expectation to hope that this book will the first of many,
About the Reviewer: Bob Williams is retired and lives in a small town with his wife, dogs and a cat. He has been collecting books all his life, and has done freelance writing, mostly on classical music. His principal interests are James Joyce, Jane Austen and Homer. His writings, two books and a number of short articles on Joyce, can be accessed at: http://www.grand-teton.com/service/Persons_Places