Review: Evolution: What the Fossils Say and Why it Matters
Work under Review
Arch-creationist Duane Gish proclaimed that fossils say "no!" to evolution. Creationists perennially make bizarre claims about the supposed deficiencies of the fossil record. This book is motivated by the challenge of "intelligent design" (ID) and the recent Kitzmilller v. Dover Area School Board case decided in federal court in Harrisburg, Pennsylvania. Don Prothero of Occidental College is a very good vertebrate paleontologist. He has written a book to provide definitive resources on exactly what the fossil record shows.
Prothero is equal to his task. He is unusually broad in his background and experiences. Although he is an expert on Late Cenozoic ungulate mammals, he has also published on planktonic microfossils. He is a wily veteran of successful debates with Gish. Like Stephen Jay Gould, he demonstrates familiarity with the Bible, and quotes it frequently to advantage. I am in awe of his ability to read the New Testament in Greek. He is well versed in the history of science and religion and makes it clear that he sees no necessary conflict between science and religion.
The book is divided into two parts. Part I (141 pages) examines exactly what we understand by evolution. Prothero considers the nature of science itself, and the relationship of evolution to biology. The biological material brims with up-to-date content, including a nice discussion of the significance of evo-devo and of hox genes. Very useful is the section aptly titled "Evolution happens all the time!" (p 113–8). He reviews contemporary examples of evolutionary change such as sockeye salmon in Washington state, three-spine sticklebacks in Alaska and Norway, codfishes in the Western Atlantic, and pesticide resistance in insects. He ends this section with a lovely quote from entomologist Martin Taylor, lamenting of farmers in the southern United States: "These people are trying to ban the teaching of evolution while their own cotton crops are failing because of evolution" (p 118).
In the chapter on systematics and evolution, Prothero hammers the point that the course of evolution is not progressive as conceptualized in such outmoded historical concepts as the scale of nature or the great chain of being but rather takes the form of a bush. Creationist insistence on missing links depends on a metaphor scientists (but not necessarily journalists) have long since discarded. He fully develops concepts of cladistics that systematists universally rely upon today.
Part II (215 pages) is the heart of the matter, a survey of the major features of the fossil record from the origins of life to the appearance of humans. I found chapter 7 ("Cambrian 'explosion' — or 'slow fuse'?") quite useful. To Darwin and his contemporaries it appeared that the geological record showed no evidence of life for an immense interval of Precambrian time, and then all of a sudden life appeared in profusion during the Cambrian Period. Since the 1940s there has been a steady increase in discoveries of soft-bodied fossils and microfossils from the Precambrian, including the famous metazoan radiation of the late Precambrian, with its now world-wide Ediacaran faunas. It is also clear that the profusion of hard-bodied fossils such as trilobites, brachiopods, and sponge-like archaeocyathids that are so apparent in rocks came about 25 million years after the beginning of the Cambrian, and was preceded by a reasonably diverse fauna of small shelly fossils that had long been ignored. Thus the Cambrian explosion turns out to be more apparent than real, and another creationist canard bites the dust!
At one time the finest example of an early tetrapod that we could use was Ichthyostega, an unequivocal amphibian. Tiktaalik roseae, described only in 2006, is as sweet an intermediate fossil as can be imagined. Although just on the fish side of the transition, this "fishapod" from the Canadian Arctic has the flattened skull of a tetrapod and a neck, unheard of in a fish. The forefins show a humerus, radius, and ulna, but bear fin-rays, not fingers. Early tetrapods such as Acanthostega and Tulerpeton show that seven or eight fingers preceded the familiar tetrapod pattern of five fingers.
The book proceeds seriatim through seminal recent discoveries in tetrapods, amniotes, dinosaurs to birds and then to mammals. Prothero points out that the evolution of horses, elucidated since the 1870s, remains one of the finest demonstrations of evolutionary change over time. Horse evolution traced over 50 million years exhibits bushiness and lack of directedness. Similar cases can be made for rhinoceros, camels, tapirs, artiodactyls, and elephants. Whale evolution has been clarified by the recent discovery of important fossils from Pakistan, especially Ambulocetus, the Eocene "walking whale", and Rodhocetus, the proto-whale with the ankle of an artiodactyl. Finally, the book documents the richness of the hominin fossil record, which has been substantially enhanced by new finds of the past decade. Prothero demonstrates atavisms in humans (including several arresting photographs of fleshy tails) that make no sense in terms of "intelligent design", but which are easily understandable as developmental anomalies revealing our evolutionary antecedents.
The book is beautifully illustrated with photos and drawings of fossils, and phylogenetic diagrams. It is enlivened with topical cartoons skewering creationists. The book is very valuable as a demonstration of the quality of the fossil record, which has improved dramatically in the past decade. It is a fine resource for those whose knowledge of either paleontology or evolutionary biology can use a little dusting off and polishing. We often accuse creationists of using outdated arguments. Reading a book such as Prothero's will ensure that we do not do the same.
I do have a complaint, however. The book preaches to the converted. Its polemical tone can become wearying and may produce the unintended effect of nudging undecided readers in the wrong direction. Poorly disguising his contempt, Prothero's rhetoric is sometimes over the top, as when he refers to "hard working, dedicated, self-sacrificing biologists who spend years enduring harsh conditions in the field" in contrast to "creationists who sit in their comfortable homes and write drivel" (p 113). Please! The facts of paleontology stand on their own. They do not need to be undermined by rhetorical shenanigans.
Department of Animal Biology
School of Veterinary Medicine
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Peter Dodson is Professor of Anatomy and Paleontology at the University of Pennsylvania, and a coeditor of The Dinosauria, second edition (Berkeley [CA]: University of California Press, 2004).