Selected Essays by Ernst Mayr (review)

Evolution and the Diversity of Life, Selected Essays: Ernst Mayr, Belknap Press of Harvard University, 1976, First paperback edition 1997, ISBN 0-674-27105-X, 711 pages.

Ernst Mayr is the grand old man of evolutionary biology with a career spanning seven decades. He was one of principal architects of the modern neo-darwinian synthesis. He is an excellent writer, albeit daunting. He is the author of numerous books, including The Growth of Biological Thought and Toward a New Philosophy of Biology.

This book is a major collection of his essays and articles. There are some 47 essays; they originally appeared from the 50’s through the early 70’s. The essays are divided into nine main categories:

Evolution
Speciation
History of Biology
Philosophy of Biology
Theory of Systematics
The species
Man
Biogeography
Behavior

As a general remark, this is not a book for someone who wants an easy read which gives him a superficial understanding. On the other hand it is, I think, accessible to the layman who has a modest acquaintance with biology and science in general. The difficulties are that he does have some dryness of style (or even a great deal for people who are uncomfortable with expository text), that he really does invade his topics with considerable detail and vigor, and that many topics are covered without there being an overall coordinated structure.

People who are concerned with evolutionary theory and biology fall into several fairly well defined camps. Rather generally we can group them into the naturalists, the theorists, and the functionalists. The functionalists can be thought of as those who study the engineering of life. Thus the molecular biochemist. The theorists are those concerned with abstract models, e.g. population genetics. The naturalists are those concerned with life and in situ. Thus the paleontologist, the taxonomist, the ecologist, and the naturalist in the field.

Mayr belongs to the naturalist camp; he was trained in ornithology; the distribution, the habits, the classification of, and the evolution of birds recur in his work. (The book includes several essays on the biogeography of birds.) However his concerns are much broader – he deals with the philosophic issues raised by biology and the theory of evolution, the history of biological thought, and the process of evolution. To these concerns he brings the perspective of the naturalist.

For example, if one reads the popular works of Richard Dawkins one notices a certain paucity of actual biology. His works are replete with theoretical models, doves and hawks, and selfish genes. The models and the arguments are orderly and neat and quite convincing within their circumscribed domain. However life is notoriously messy and complex; one is left wondering how much, if any, applies to real life.

If one turns to Mayr, on the other hand, the arguments and discussions are butressed with biological detail. When Mayr discusses speciation via founder populations the argument is augmented by accounts of field studies, e.g., species and subspecies counts in specific environments. Issues such as modes of dispersion and specific geographic isolating factors are carefully considered. Speciation patterns are not merely postulated; the predicted patterns are carefully checked against real observation. The resulting text is certainly drier (tables of numbers are seldom enthralling reading) than that of flashier writers; however one gets a sense of real substance in the discussions.

His discussions of the philosophy of biology may be of interest to the general reader who is familiar with classical philosophy but not the complexities of biology. Briefly, he argues that classical essentialism and nominalism are both inappropriate and were real stumbling blocks in the development of biological thought. Rudely, essentialism postulates that individuals have a type essence, that they are shadows cast in Plato’s cave. Rudely, nominalism postulates that each individual is unique, that all categories are ad hoc. Each mode of thought has its uses. In biology, however, neither works well. The alternative is populational thinking. Each individual organism is unique and distinct; however they fall into populations which are united by interbreeding and common descent. The populations in turn do not have Platonic essences. This thesis is developed at length in some of his other works; in the essays here it is introduced.

Mayr makes an interesting observation about the Greek eidos and the interpretation of Aristotle’s work. Briefly, he remarks that Aristotle’s thought had a much more biological basis than Plato’s and should be considered from that standpoint. Thus he claims that eidos in Aristotle is closer to the modern sense of a genetic program (p400):

“No other ancient philosopher has been as badly misunderstood and mishandled by posterity as Aristotle. His interests were primarily those of a biologist and his philosophy is bound to be misunderstood if this fact is ignored. Neither Aristotle nor most of the other ancient philosophers made a sharp distinction between the living world and the inanimate. They saw something like life or soul even in the inorganic world. If one can discern purposiveness and goal direction in the world of organisms, why not regard the order of the Kosmos as a whole as also due to final causes, that is, as due to a built-in teleology? As Ayala (1970) said quite rightly, Aristotle’s ‘error was not that he used teleological explanations in biology, but that he extended them to the non-living world.’ Unfortunately, it was this latter teleology that was first encountered in the sixteenth and seventeenth centuries (and at that in the badly distorted interpretations of the scholastics). This is one of the reasons for the violent rejection of Aristotle by Bacon, Descartes, and their followers.

Although the philosophers of the last 40 years acknowledge quite generally the inspiration that Aristotle derived from the study of living nature, they sill express his philosophy in words taken from the vocabulary of Greek dictionaries that are hundreds of years old. The time would seem to have come for the translators and interpreters of Aristotle to use a language appropriate to his thinking, that is, the language of biology, and not that of sixteenth century humanists. Delbruck (1971) is entirely right when he insists that it is quite legitimate to employ modern terms like “genetic program” for eidos where this helps to elucidate Aristotle’s thoughts. One of the reasons why Aristotle has been so consistently misunderstood is that he used the term eidos for his form-giving principle, and everybody took it for granted that he had something in mind similar to Plato’s concept of eidos. Yet the contexty of Aristotle’s discussions makes it abundantly clear that his eidos is something totally different from Plato’s eidos (I myself did not understand this until recently). Aristotle saw with extraordinary clarity that it makes no more sense to describe living organisms in terms of mere matter than to describe a house as a pile of bricks and mortar. Just as the blueprint used by the builder determines the form of a house, so does the eidos (in its Aristotelian definition) give the form to the developing organism, and this eidos reflects the terminal telos of the full-grown individual….”

This is a fat book, 718 pages. It is not really suitable for the enthralled straight through read in the style of the epic novel. It is a book to be read in stages, to be read in parts, to be set aside, and then taken up and read some more. It is not for everyone, of course. One has to have a real interest in biology and a certain amount of patience. The difference between Mayr and a writer like Stephen Gould is this:

When one reads the essays of Gould, they are consumed easily and pleasantly and one is left with the impression that one knows things. When one turns to Mayr, the going is not so easy, one gets a great deal more than is offered by Gould, and one is forcefully reminded how little one really knows.

As I have said, these essays were written in the period 1950-1975. Much has happened since then in biology, particularly in molecular biochemistry. None-the-less, the essays stand up surprisingly well, in good part because Mayr does have the perspective of a naturalist.