The third edition of Conceptual Issues in Evolutionary Biology is welcome. This anthology covers a wide variety of subjects concerning the philosophy of biology and the theory of evolution. The essays published in this volume (twenty-seven papers divided in thirteen sections) are not only interesting for the student of philosophy, but they are also approachable — and I think illuminating — for the layperson, who will find challenging discussions about the theory of evolution, evolutionary psychology and ethics, the evolution of culture, the debate on the reality of races, and female sexuality.

During 60s and 70s, several philosophers — amongst them Popper and Smart — claimed that the theory of evolution is not falsifiable and is based on circular explanations. They argued that the theory of evolution is founded on the assertion that the fittest individuals will survive, but the fittest individuals are defined as the individuals that actually survive; therefore the theory of evolution asserts a trivial truism. In the first section of the anthology Mills and Beatty provide an interpretation of "fitness" based on the propensity account of probability: "the fitness of an organism is its propensity to survive and reproduce" (9). Using this account of fitness, the authors can answer the charges of circularity levelled against the theory of evolution. In the second paper of this section, Sober points out that this reconstruction of fitness leaves an open question: must we consider the probability to reproduce in the first generation, or in the second, or perhaps the probability of leaving offspring after one hundred generations? Sometimes a one‑generation time frame is inadequate, and thus we must distinguish between a short-term fitness and a long‑term fitness. In particular situations long‑term fitness depends on the size of the population: fitness is thus a holistic property. This characteristic opens a new question: does the evolution act on individuals or on groups of individuals? The analysis of the units of selection is the subject of the second section. We are introduced in a very interesting field, whose results and debates echoed in popular press, as testified by Dawkins' book The Selfish Gene. The classical (i.e. Darwinian) picture of evolution as a process acting on individuals is challenged by the consideration that selection and adaptation operates not only on individuals, but also on populations and genes. Evolution thus occurs at different levels: at the level of genes, of individuals, and of populations. These reflections open the way to a pluralistic conception of selection, adaptation, and evolution.

We can find other examples of pluralism in contemporary biology. Theoretical pluralism, advocated by Beatty in "The Evolutionary Contingency Thesis", asserts that different theories are required in order to explain biological phenomena. "There is no single theory or mechanism — not even a single synthetic, multi-causal theory or mechanism — that will account for every item of the domain. This is not a matter of insufficient evidence for a single theory; rather, it is a matter of evidence that multiple accounts are required" (229). Beatty's paper belongs to the sixth section of the anthology, dedicated to the analysis of laws in biology. This is an entire new section, added for the third edition. I have found interesting the two papers selected for this section, thought I cannot subscribe Sober's introduction, in which he accuses logical empiricism to have encouraged the idea that biology contains no law and that it was "deficient as a science" (xv). Only with the demise of logical empiricism — Sober says — biology was recognized as a science not inferior to physics. When I was a student of philosophy at the University of Rome — it was twenty-five years ago — I studied Ruse's book The Philosophy of Biology, a typical logical empiricist account of biology. Ruse asserted that biology is neither different nor inferior to physics; biology incorporates the same kind of laws that are used in physics. Perhaps I and Sober have read different books.

Even in the debate about natural kinds pluralism seems a winning strategy. A criticism of essentialism is advanced in the eight section of the anthology, following Mayr's line of thought (essentialism is the best known alternative to pluralism; it claims that natural kinds are defined in a unique way by means of essential intrinsic properties). The relevance of pluralism is evident in the analysis of the concept of species, which is the subject of the ninth section. Hull's seminal work "A Matter of Individuality" argues that species are not kinds but individuals. Baum and Donoghue analyse different species concepts, and contrast the character-based approaches (that define species according to some shared properties) with the history-based approaches (that consider genealogical and evolutionary relationships of organisms).

I conclude this review with a mention of Elisabeth Lloyd's "Pre-theoretical Assumptions in Evolutionary Explanations of Female Sexuality", in the section (added for the third edition) about women in the evolutionary process. According to Lloyd, the typical explanation of female orgasm maintains that orgasm is an evolutionary adaptation in order to favour the reproductive activity, in spite of the evidence — from both humans and primates — that female orgasm is not associated with reproduction. The problem with this kind of explanation is that "it is simply assumed that every aspect of female sexuality should be explained in terms of reproductive functions" (161). Such an assumption is due to the biased influence of social beliefs. Lloyd's paper calls for a new perspective in philosophy of science: "we need a view of science that is more sophisticated" (169), because traditional philosophy of science lacks the capacity of identifying and explaining the role of pre-theoretical and social beliefs in scientific researches.

Conceptual Issues in Evolutionary Biology is an interesting anthology that collects stimulating philosophical papers; it points out the many open questions in the field of philosophy of biology and illustrates the value of a pluralistic approach.

© 2007 Mauro Murzi

Mauro Murzi, Dott. is primarily interested in philosophy of science and history of logical positivism. Astronomy is his main hobby, and now he is working on philosophical implications of contemporary astronomy.

Categories: Genetics, Philosophical