EVOLUTION AND ITS MAJOR TRANSITIONS

Review of The Major Transitions in Evolution Revisited, edited by Brett Calcott and Kim Sterelny, Vienna Series in Theoretical Biology, MIT Press, 2011 (ISBN 978-0-262-01524-0). Theoretical evolutionary biology has been going through both a Renaissance and an expansion over the past several years, and some of the most intriguing contributions have come from the Vienna Series published by MIT Press. Although the classical view is that population genetics theory is the centerpiece of any theoretical biology (e.g., Lynch 2007), an expanded concept of what it means to do theory in biology has been proposed (Pigliucci 2008), of which population and quantitative genetics represent but a small (if very important) component. The volume recently edited by Brett Calcott and Kim Sterelny interestingly, both philosophers of science picks up where the now classic volume on evolutionary transitions by MaynardSmith and Szathmary (1997) left off and attempts to see where we are when it comes to the really big picture in evolutionary theory. As it is typically the case with such edited volumes, the goals the editors set up to accomplish are necessarily only partially achieved, because each contributor is more or less free to roam afar from the main topic of discussion, sometimes in areas whose logical link with the topic at hand is tenuous at best. Nonetheless, there is much food for thought in this book, which would make for an extraordinarily interesting graduate-level seminar, especially if accompanied by the original Smith-Szathmary volume. (Ironically, one of the farthest afield excursions is due to Szathmary himself, who was called to comment at the end on the entire volume and instead chose to pursue with his coauthor, Chrisantha Fernando an only very partially related line of inquiry having to do with applying evolutionary principles to the functioning of the human brain.) I must admit of never having been too fond of the idea of "major transitions," understood as a somewhat coherent set of phenomena that in some meaningful way admit similar underlying explanations. The editors of this volume write that "Among the major transitions are episodes of the creation of new kinds of evolutionary agent: eukaryotic cells; multicelled animals; social insects" (p. 3). Well, perhaps, but this opens up the Pandora box of what counts as an "evolutionary agent," and why some transitions do not seem to create new kinds of agents (the origin of language for instance). Perhaps more appropriately, Calcott and Sterelny focus on three themes that do seem to underlie the Smith-Szathmary volume, and that get major booking in this new collection: the expansion of hereditary mechanisms; the evolution of new levels of biological individuality; and the generation of variation. These are arguably some of the major issues in evolutionary biology, and they have received only partial and largely unsatisfactory treatment within the now more than half century old framework of the Modern Synthesis (Pigliucci and Muller 2010). Although much debate is still going on about all three issues highlighted by Calcott and Sterelny, it seems beyond reasonable question at this point that: (1) hereditary mechanisms have been evolving and expanding, from the relative simplicity of the RNA world to the modern panoply of genetic, epigenetic, behavioral, and cultural inheritance (Jabloňka and Lamb 2005); (2) we cannot do evolutionary theory without a serious understanding of multilevel selection, pace historical disagreements on old fashioned and new fangled group selection (Okasha 2006); and (c) the way in which variation is generated itself evolves in interesting ways, a concept captured under the general heading of "evolvability" (e.g., Woods et al. 201 1). The real challenge is to make sense of these and many other related ideas within a coherent conceptual framework.