Evolution for Beginners?
In 1928, when the Cyclops Mountains of New Guinea were mostly unexplored by Western scientists, an undaunted biologist named Ernst Mayr undertook the first field survey of the indigenous birds of the area. It was astonishing work for many reasons, not least because the region was forbidding and remote and reportedly inhabited by ferocious tribal peoples. That experience, and others to follow, gave Mayr a grasp of the breadth and elegance of evolution in action few could rival.
By the 1930s and 1940s, Mayr, together with G.G. Simpson and Theodosius Dobzhansky, was re-creating evolutionary theory and its applications. By the 1960s, Mayr was writing classics of evolutionary theory such as the one my generation cut its intellectual teeth on, “Animal Species and Evolution.” He has sorted out deeply tangled taxonomic muddles, written wisely on the hows and whys of evolution and illuminated many of the subtleties of evolution throughout his career. At 97, Mayr is now the Grand Old Man of evolutionary theory and the last living architect of the so-called new synthesis that brought Darwinian theory--or more properly, theories, as he points out--together with population genetics and paleontology.
Thus it was with enormous anticipation that I opened “What Evolution Is,” Mayr’s latest work. It is touted in its preface as “a concise, reader-friendly account” of evolution. At this late phase of his career (long may it continue), Mayr proposes to give us a book meant for “anyone, biologist or not, who simply wants to know more about evolution ... [for] those who accept evolution, but are in doubt as to whether the Darwinian explanation is the correct one ... And finally [for] creationists who want to know more about the current paradigm of evolutionary science if for no other reason than to be better able to argue against it.” Mayr announces that the existing volumes written by others are too specialized, “too technical, and use too much jargon” (they are) and his book will be different.
Sadly, it is not. Mayr starts off well with a section called “What is the evidence for evolution?” that is clearly written but does not answer the question. Instead, he simply pronounces that the evidence for evolution is “now quite overwhelming,” refers readers to other works where the evidence is actually discussed and reviews the types of evidence that have been studied. Mayr’s explanations and definitions are deliciously concise. Of course, the shortcoming of concise definitions is that they fail to provide operational criteria that would let the reader actually use them. Still, Mayr’s explanations of the basic principles are admirably clear and that is the first step to proposing and agreeing upon operational criteria.
What of Mayr’s avowed readership? All too often readers are expected to take his word for it. Mayr pronounces that evolution is “irrefutable” and that “there is no other natural explanation than evolution for the facts presented [here],” assertions that are unlikely to change the minds of those inclined to endorse supernatural or godly explanations for the way things are on Earth. For the non-specialist believer in evolution who wants to learn more or hoping for clarity, there is a different problem. Mayr has a very optimistic opinion of the knowledge of his readership, or else he credits them with a great willingness to spend time with the glossary and a good encyclopedia before reading on.
In a brilliant section of the book, for example, in which Mayr takes what we know of genetic variation and inheritance and boils it down to 17 basic principles, the concepts are stated and explained in a mere two pages with four figures. This is a tour de force: Every biology teacher, every undergraduate in a biology class and particularly every graduate student in an evolutionary discipline must read and memorize these principles. But for the general reader, they can be stiff going. Principle 16 reads: “A gene has a complex structure, consisting of exons, introns, and flanking sequences (Fig. 5.4).” The inquisitive reader has perhaps never heard of exons, introns or flanking sequences and finds these topics are not included in the index or the glossary.
Perhaps, too, this same reader does not know what a gene looks like or how much of the more familiar DNA molecule a single gene comprises. Turning dutifully to Fig. 5.4, the reader finds three horizontally oriented strips colored in shades of gray and labeled with the terms “upstream,” “downstream,” “Poly-A addition site,” “initial transcript (pre-mRNA),” “5’ Cap,” “leader,” “start codon,” “stop codon,” “trailer,” “Poly-A tail.” Yet none of these terms is defined. The caption identifies the source of the figure and says: “Structure of a eukaryotic gene, with its exons, introns, and flanking sequences.” This is not helpful to the uninitiated. In fact, most of the figures have been borrowed from other publications--something nearly everyone writing for a general public does--but they are not well-explained and not always good illustrations of the point.
Less satisfying still is Mayr’s presentation of a number of specific topics, such as his capsule summary of the debate over the dinosaurian origin of birds. It owes much to a minority view that has been seriously undermined in recent years by the discovery of numerous species of feathered dinosaurs. To discuss the evolutionary origin of birds and not to mention these new finds is incomprehensible. A chapter on human evolution is equally dated: Mayr discusses none of the hominid species discovered after 1990, though he acknowledges there have been at least six since 1994. There is no earthly excuse for this, not even Mayr’s dumbfounding assertion that “no one has yet attempted to properly place them [the new species] in a new hominid phylogenetic tree.” (My friends and colleagues who have been responsible for describing and naming these species will be greatly disconcerted to know that the phylogenetic diagrams in their papers in Nature, Science and similar journals do not constitute proper attempts to construct a new phylogenetic tree for the hominids.)
The problem may be that Mayr relies particularly for his information on a 1996 book about human evolution by a well-known expert on fossil shells, Steven Stanley, and on a 2001 article by a behavioral scientist who studies great apes, Richard Wrangham. Wrangham and Stanley are able and well-respected scientists, but their writings are not the best choices for breadth, balance of coverage, or up-to-date accuracy about human evolution. As a result I can’t recommend it as an overview of human evolution.
Does this mean that the book is a failure, the revelation of an aging scientist who has lost his grip? Not at all. It is an excellent book in its way, albeit one that is too technical for its intended audience. Nonetheless, it is possibly the last book we will ever see by this man who has an extraordinary grasp of the larger pattern of evolution as we currently understand it. When Mayr was a German student in the early 20th century, professors professed unchallenged, and everyone else obediently believed the words of the great men. Now Mayr--unquestionably a great man--attempts to follow suit and convince by personal authority and assertion; this approach may not sit well with 21st century readers.
Still, Mayr has told us “what evolution is,” as he has been telling us for more than 60 years. I will not keep his book for his summary of the evolution of specific groups, which is flawed, but for this glimpse of how a great evolutionist sees the grand and ever-changing scheme of life. For that alone, this book has earned its place on my bookshelf, where it will stay within handy reach.
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Pat Shipman is the author of numerous books, including “Taking Wing: Archaeopteryx and the Evolution of Bird Flight” and “The Man Who Found the Missing Link: Eugene Dubois and His Lifelong Quest to Prove Darwin Right.” She is a professor of anthropology at Pennsylvania State University.
