The Hamiltonian view of social evolutionThe philosophy of social evolution,

Birch Jonathan

, Oxford University Press, Oxford (2017), p. 224, Hardcover, ISBN: 9780198733058

In the obituary of her mentor Bill Hamilton, the American entomologist and evolutionary biologist Marlene Zuk wrote that the difference between Hamilton and everyone else was “not the quality of his ideas, but their sheer abundance” (Zuk, 2000). The proportion of his ideas that were actually any good was about the same as anyone else, “the difference between Bill and most other people was that he had a total of over one hundred ideas, with the result that at least ten of them were brilliant, whereas the rest of us have only four or five ideas as long as we live, with the result that none of them are”. Hamilton indeed had many good ideas. Over the years he made substantial contributions to the study of the origin of sex, sex ratios, genetic conflicts, and the evolution of senescence (Ågren, 2013). His best idea, and the one that bears his name, is about the evolution of social behaviour, especially altruism. Hamilton's Rule, and the related concepts of inclusive fitness and kin selection, have been the bedrock of the study of social evolution for the past half century (Fig. 1).

Jonathan Birch's recent book The philosophy of social of evolution is a superb exploration of philosophical implications of Hamilton's work. The philosophy of biology has a long-standing close relationship with evolutionary biology (maybe too close, some have argued (Pradeu, 2017)). Within evolutionary biology, the study of social evolution has been especially important. In a recent interview (Marshall, 2016), Elliot Sober, one of the founders of the field, described how he came to the philosophy of biology after being intrigued by William Wimsatt's review of George C. Williams's classic critique of group selection Adaptation and natural selection (Williams, 1966; Wimsatt, 1970). Pioneering books in the field of philosophy of biology, like Sober's The nature of selection (Sober, 1984), Elizabeth Lloyd's The structure and confirmation of evolutionary theory (Lloyd, 1988), and Daniel Dennett's Darwin's dangerous idea (Dennett, 1995) all dedicated large chunks to the issues of causality, altruism and selfishness, and the levels of selection, raised by influential books on social evolution, especially Williams' Adaptation and natural selection and Richard Dawkins' The selfish gene (Dawkins, 1976). These authors belong to the finest tradition in the philosophy of science. They are deeply informed about the biology in question and their work contributed to the advancement of not only philosophy of biology but practice as well. Early on in The philosophy of social evolution (p. 9), Birch aligns his book to this tradition, to which Brandon (1990), Okasha (2006), and Godfrey-Smith (2009) also belong, and in my view the book fits squarely in that company.

In The philosophy of social Evolution Birch provides a comprehensive introduction to the conceptual foundations of the Hamiltonian view of social evolution, and a passionate defence of its enduring value in face of recent high profile criticism. The book is divided into two parts: Foundations (five chapters) and Extensions (three chapters). The early parts lay out the Hamiltonian approach to social evolution. In particular, Birch takes his starting point in David Queller's formulation of Hamilton's Rule (Queller, 1992), dubbed Hamilton's Rule General (HRG). This version is central to the arguments throughout the book and in this review essay I will therefore first outline HRG and its derivation. With this in place, I will then navigate through the intense disagreements that Hamilton's Rule, including HRG, generates and evaluate Birch's central argument of the book that HRG serves as an organizing framework for social evolution research under which we can compare and interpret more detailed causal models. The book also contains novel insights on group vs. kin selection models, conceptions of social fitness, and recent developments in the study of the origin of multicellularity and cultural evolution. These chapters are all stimulating, but in the interest of space I will spend the remainder of the review on what I take to be three of the most exciting implications of Hamilton's thinking raised by Birch: (1) the extension of Hamilton's Rule to mobile genetic elements, (2) maximization of inclusive fitness models and the idea of adaptation as organism design, and (3) the relationship between Hamilton's approaches to social behaviour and the gene's-eye view of evolution.