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Toward a New Philosophy of Biology - review

by Jack P. Hailman

s most readers of Auk are aware, Ernst Mayr is one of the great ornithologists of this century, and he is one of the foremost evolutionary biologists of our time as well. So when he writes, it behooves us to read. Moreover, the present book was issued in Mayr's ninth decade of life, reminding us of how long his contributions have provided a guiding light of modern evolutionary thought.

Does biology need a new philosophy? Mayr begins by arguing that it does, or perhaps that those who are not evolutionary biologists need to recognize more fully that organic evolution is the central theme of the biological sciences. So he embarks on a voyage through natural selection, adaptation, Darwin's thinking, biological diversity, species and speciation, and macroevolution, and he concludes with two essays of historical perspective in order to show the way. This is not a new book, in the sense of his 1982 opus, "The Growth of Biological Thought," but rather a collection of previously published articles, book reviews, and essays that have been edited to update them and to remove redundancy. The works are arranged carefully and integrated with new bridge material to provide the volume with a coherence too rarely found in this genre, so even those who have read some of this material when it appeared will want to consider it again within the new context. California produces high quality wines year after year; the date on the label tells us the age of the wine, but the vintage year is not so important. So let it be with Mayr.

Every essay in this book (there are nearly thirty) could easily be the subject of its own review, as each deals with one or more issues of real substance in evolutionary biology. There is no woodland without its individual oaks, maples, pines and their ilk, but the trick is to see the forest despite the trees. Whether those of us who are evolutionary biologists like it or not, our science is not fully accepted in the community of scholars for much the same reasons that we find it an absorbing life's endeavor. Why is it that evolutionary biology is "different," and how well has Mayr identified and dealt with the global issues? I shall ignore largely historical problems such as vitalism, which Mayr considers just at the start, and also the many smaller issues that do not pierce the core. Forgive necessary oversimplification in the attempt to treat the problem under just four rubrics: empiricism, reductionism, historical load, and operationism.

In discussing evolution with biologists and other scientists who profess reservations about our science, I have found that they ask first after the evidence that selection is the driving force of evolutionary change. Mayr asserts (p. 3) that "The Darwinian mechanism of natural selection with its chance aspects and constraints is fully sufficient" to explain teleological-like aspects of evolution in particular, and indeed all the results of evolution in general. A major stumbling block to understanding selection processes is the unit of selection or, as Mayr prefers, selection's target. Episodically through the book, Mayr hammers home the point that the individual is the target, and he has strong but deserved words about "the silent assumption of the mathematical population geneticists that the gene is the unit of selection" (p. 119). I find essay 7 on group selection somewhat angential in focusing on different kinds of "groups" while losing track of the "selection" part. The vagueness of the notion of "competition among species" lies at heart here, for unless the species has a heritable emergent property of its own that potentiates its continuance at the expense of another species, "competition among species" is no more than competition among individuals of different species. Still, logical problems aside, Mayr nowhere confronts head-on the philosophical need in science for direct empirical evidence. He cites (p. 96) Endler's 1986 book as providing the "abundant evidence for the occurrence of natural selection in nature" but that ambitious compilation reviews the works of true believers. What we need is a philosophy for empirically testing the existence of selection in such a way that one possible outcome of the test is outright rejection of our beloved hypothesis.

Mentioning emergent properties brings me to the second of four rubrics, for which we can use the term reductionism. As Mayr rightly points out, many mechanistically inclined biologists see as a guiding principle the reduction of life to "understood" mechanisms of physics and chemistry. These colleagues fail to realize that the interactions among parts provides the whole with properties that "emerge" with its existence. As someone, perhaps Sir Arthur Eddington, said: we think we understand "two" after making a thorough study of "one" because one and one are two, but we forget that we must also make a thorough study of "and." Mayr does not devote a lot of space to the reductionist problem per se, but he treats it implictly throughout the book.

The third major issue that makes evolutionary biology different from most sciences, although not uniquely so, is its pervasive historical underpinning. There is a bridge in New York state unlike any over which you have driven a vehicle. It is impossible to understand the design of this bridge until you know that it was originally built as an aqueducto carry the Erie Canal, and later modified as a roadbed. And so it is with every organism on earth today: its ancestors were different, functional organisms. Mayr confronts the historical constraints of evolution throughout the book, although perhaps not with the verve and evidence I would have desired. Essay 4, on the "Probability of Extraterrestrial Intelligent Life," is a particular gem. It shows us, as no other comparable section of the book, how the evolutionary biologist arrives at vastly different predictions from those of the physical scientist. The problem with most science fiction movies is that they have the mindset of astronomer Donald Menzel rather than that of biologist Ernst Mayr.

I have saved for last the bone that I am willing to contend. Early in this century, physicists grappling with things that they could not see came to realize this: an entity or process had communicable meaning to fellow physicists only within the context of the operations by which it was measured. From this origin, Nobel laureate Percy Bridgman developed the philosophy of operationalism which today pervades most of science. Evolutionary biology stands out like a very sore thumb. Most of contemporary biology is so thoroughly operational that modern students take it as a fact of life without realizing that things were not always this way. Barely a generation ago, one could define the home range of an animal as where it spent its time, but today one specifies the methods of recording where it was and when, and then makes explicit how home range was calculated from the data, say, by connecting spatial points to form the largest possible polygon. What a philosophy of evolutionary biology needs, above all else in my view, is operational approaches. We stake a difficult claim for a legitimate science among peers when adaptedness is defined (p. 135) as "the morphological, physiological, and behavioral equipment of a species or of a member of a species that permits it to compete successfully with other members of its own species or with individuals of other species and that permits it to tolerate the extant physical environment." (For the curious, an operational alternative may be found in my 1988 essay in "Evolutionary Processes and Metaphors," edited by M. W. Ho and S. W. Fox.) Evolutionary biology is so immensely complex that it has moved at a snail's pace toward operational thinking. My complaint is not that Mayr himself has a conceptual rather than operational intellect, for he was exactly appropriate to his time, namely most of this century. My complaint is that this book shows not the slightest hint that lack of operationism stands today as the largest philosophical impediment to new advances in evolutionary biology.

To summarize the summary, "Towards a New Philosophy of Biology" rates high in three of the four general issues I have dissected out as being particularly crucial. It is, as the overworked closing sentiment goes, "must" reading for anyone interested in evolutionary biology. And that, I hope, includes us all. — JACK P. HAILMAN.

[ Jack P. Hailman, "Reviews," Auk 106 (October 1989): 751-752. ]

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