PREFACE

Evolution is the most important concept in biology. There is not a single Why? question in biology that can be answered adequately without a consideration of evolution. But the importance of this concept goes far beyond biology. The thinking of modern humans, whether we realize it or not, is profoundly affected—one is almost tempted to say determined—by evolutionary thinking. To offer a volume dealing with this important subject thus requires no apology.

However, someone might say, “Is not the market already saturated with books about evolution?” As far as the sheer quantity of published volumes is concerned, the answer might well be “Yes.” Particularly there are several excellent technical texts for biologists who specialize in evolutionary studies. There are also splendid defenses of evolutionism against attacks by creationists, as well as excellent volumes on special aspects of evolution, such as behavioral evolution, evolutionary ecology, coevolution, sexual selection, and adaptation. But none of them quite fills the niche I have in mind.

This volume is meant for three kinds of readers. First and foremost, it is written for anyone, biologist or not, who simply wants to know more about evolution. Such a reader is quite aware how important this process is but does not understand exactly how it works and how one can answer some of the attacks against the Darwinian interpretation. The second group of readers consists of those who accept evolution, but are in doubt whether the Darwinian explanation is the correct one. I hope to answer all the questions this kind of reader is apt to ask. And finally, my account is directed to those creationists who want to know more about the current paradigm of evolutionary science, if for no other reason than to be able to better argue against it. I do not expect to convert this kind of reader, but I want to show him or her how powerful the evidence is that induces the evolutionary biologist to disagree with the account presented in Genesis.

The existing volumes intended to fill these needs have some of the following shortcomings. All of them are rather poorly organized and fail to present a concise, reader-friendly account. Most of them are not as didactic as they should be, because a difficult subject such as evolution should be presented as answers to a series of questions. Nearly all of them devote too much space to specialized aspects of evolution, such as the genetic basis of variation and the role of sex ratios. Virtually all of them are too technical and use too much jargon. About one-quarter of the content of all recent major evolutionary texts is devoted to genetics. I agree that the principles of genetics must be thoroughly explained, but there is no need for so much Mendelian arithmetic. Nor should space be wasted on arguing for or against obsolete claims, such as that the gene is the object of selection, or to a refutation of extreme recapitulationism (the idea that ontogeny recapitulates or repeats phylogeny). On the other hand, several of these texts do not give adequate space to an analysis of the different kinds of natural selection, particularly selection for reproductive success.

Most existing volumes on evolution have two other weaknesses. First, they fail to point out that almost all evolutionary phenomena can be assigned to one or the other of two major evolutionary processes: the acquisition and maintenance of adaptedness, and the origin and role of organic diversity. Although both take place simultaneously, they must be analyzed separately for a full understanding of their respective roles in evolution.

Second, most treatments of evolution are written in a reductionist manner in which all evolutionary phenomena are reduced to the level of the gene. An attempt is then made to explain the higher-level evolutionary process by “upward” reasoning. This approach invariably fails. Evolution deals with phenotypes of individuals, with populations, with species; it is not “a change in gene frequencies.” The two most important units in evolution are the individual, the principal object of selection, and the population, the stage of diversifying evolution. These will be the major objects of my analysis.

It is remarkable how often a person who is trying to solve a particular evolutionary problem goes through the same sequence of unsuccessful attempts to find the solution, as has the whole field of evolutionary biology in its long history. Let us remember that our current understanding of evolution is the result of 250 years of intensive scientific study. Anyone trying to understand the solution of a given evolutionary problem may be greatly helped by considering the steps (many of them unsuccessful) by which the valid answer was finally found. It is for this didactic reason that I frequently present in considerable detail the history of the advance toward the solution of a challenging problem. Finally, I pay particular attention to human evolution and discuss to what extent our improved understanding of evolution has affected the viewpoints and values of modern humans.

What I have aimed for is an elementary volume that stresses principles and does not get lost in detail. I try to remove misunderstandings, but do not devote excessive space to ephemeral controversies, such as the role of punctuated equilibria or neutral evolution. Also, there is no longer any need to present an exhaustive list of the proofs for evolution. That evolution has taken place is so well established that such a detailed presentation of the evidence is no longer needed. In any case, it would not convince those who do not want to be persuaded.

 

Ernst Mayr
Harvard University