Contributions to Zoology, 74 (1/2) 209-211 (2005)

Short notes and reviews

Combating footnote status in evolutionary theory

Ronald A. Jenner Section of & Ecology, University of California, Davis, CA95616, USA (e-mail: rajenner@ucdavis. edu)

Review of: Biased Embryos and Evolution, by empirical and theoretical information generated Wallace Arthur. Cambridge University Press, 2004, within the mushrooming discipline of evolutionary xiii + 233 pp. ISBN 0 521 54161 1 (Paperback). development biology, or, in short, evo-devo. De- pending on the reader’s background, they can then On 11 May 2004, Wallace Arthur presented a char- choose to flesh out Arthur’s conceptual framework acteristically engaging seminar at the Department with intellectually more taxing and empirically of Zoology of the University of Cambridge in or- more dense works such as Gerhart and Kirschner der to promote his new book Biased Embryos and (1997), Davidson (2001), Minelli (2003), and Wilkins Evolution. After the lecture the speaker and his au- (2002). dience adjourned to the University Museum of Zo- The core question in Arthur’s book is: what de- ology for the official launch of the book. There, termines the direction of evolutionary change? A amidst wine and canapés, the flocked friends and resounding “!” will certainly be collected colleagues were given the opportunity to the most common answer to this question from the purchase, with a considerable reduction in prize of educated layman to most professional biologists. course, the first copies of Arthur’s book, which the However, Arthur labels this expected answer as author dutifully signed in between his munching of “overly Darwinian” (p. 10). While not denying the snacks. The festivities included mercifully little uncontested importance of natural selection as one speechifying, with the notable exception of Arthur’s factor influencing evolutionary change, Arthur managing editor at Cambridge University Press, considers natural selection to be, at best, only half who made a salient point: what set Arthur’s book the answer. Arthur (p.25) writes: “many of us feel apart for him from most other popular science books that something is missing; that selection is not was that the entire manuscript of the book was read enough; that the actualization of some creatures, in just a single sitting. This feat is certainly not the together with the failure of others to emerge from prerogative of merely the most avid bookworms, the realm of the possible, requires something else because Arthur’s refreshingly uncluttered prose al- – something internal that interacts with selection lows an effortless consumption of the book in one in a particular way.” Although I would hesitate to or just a few sessions by any interested reader. label Arthur’s more complete answer as “revolu- The book’s uncomplicated style is well tailored tionary,” as is dramatically claimed on the back to the intended broad audience of “students and the cover of the book, the central ingredients of general reader,” but the book is certainly not all Arthur’s perspective justly merit being called “as- style and no content. Biased Embryos and Evolu- saults on the modern synthesis” (p. 74). tion is an enjoyable and instructive read even for The monolithic core of modern Neo-Darwinian dyed-in-the-wool professional biologists. In my theory is the central role assigned to the functional view, this book is the best choice currently availa- and external mechanism of natural selection, which ble for an easy, short, and minimally intimidating acts on raw variation between individuals in adapt- introduction to the challenges posed to current ev- ing organisms to changing local environments. olutionary theory by the accumulating corpus of serve as the principal source of variation

Downloaded from Brill.com09/24/2021 08:16:07PM via free access 210 R.A. Jenner – Combating footnote status in evolutionary theory between different individuals. These variations, sleek book full of insightful introductions to the upon which natural selection acts, are generally as- essential concepts of evo-devo. A partial list in- sumed to be not only copious, but also undirected cludes developmental reprogramming, internal with respect to the direction of adaptive change and selection and co-adaptation of an organism’s parts, of small phenotypic effect. These presumed char- the existence of mutations with phenotypic effects acteristics have been taken to imply that natural of different magnitudes, gene duplication and func- selection is the most important causative agent un- tional divergence, co-option, accumulation of hid- derlying significant evolutionary change, and the den genetic variation, heterochrony, the structure origin of evolutionary novelties. of adaptive landscapes, as well as phylogenetic Arthur builds a case against this orthodox view methods, metazoan phylogeny, homeobox genes, by explicitly emphasizing several heretofore ne- comparative study of expression patterns of devel- glected internalist themes that require us to focus opmental genes, and . In addition, the not just on the interaction between organisms and book is sprinkled with pertinent discussions of the their external environment, but also on the role of history of biology, and revealing personal reminis- organisms themselves as internal determinants of cences from Arthur’s own career. the direction of evolutionary change. For example, Throughout his book Arthur is refreshingly can- Arthur points out that not all mutations have only did about his intellectual commitments, personal very small effects on resulting . He also interests and biases, the supposed novelty of his argues that the variation offered to the scrutiny of views, and how much they depart from perceived natural selection is not so unconstrained, or un- orthodoxy. He clearly shows that a universal con- structured, as to be essentially inconsequential to sensus about the factors responsible for the direc- the possible directions of evolutionary change. tion of evolution is elusive. Arthur’s view is mere- Therefore, in order to understand the direction of ly one of a variety of different opinions that range evolutionary change, Arthur impels us to study the from the ultimate reductionism of Davidson (2001), origin and structure of the variation offered to nat- who argues that “the study of the mechanisms by ural selection. Because evolutionary changes in which animal body plans evolve” in time will just the are necessarily effected through “be regarded as a branch of regulatory genomics”, changes in development, Arthur focuses on what to the expansive view of Vermeij (2004), who ar- he calls “developmental bias.” He defines develop- gues that the pattern of evolutionary history is mental bias as (p. 213) “non-randomness in the largely determined by universally operating eco- variation (both discrete and continuous) in devel- nomic principles that are equally applicable to hu- opmental trajectories upon which natural selection mans and the biosphere. acts.” Before the blossoming of evo-devo, such in- Although the absence of mathematics or the use ternalist explanations for the direction of evolu- of a conversational style may not convince all tionary change were at best awarded the status of readers of the validity of Arthur’s thesis, it should footnotes in evolutionary theory. However, the sig- be noted that his plea for a revision of evolutionary nificant revision of evolutionary theory proposed theory is not a lonely cry. In fact, the unquestioned by Arthur necessitates the promotion of these is- hegemony of natural selection as the sole locus of sues from mere acknowledgements in the margins evolutionary causality, with adaptation signifying of orthodoxy to fully-fledged focal points of re- the fit of organisms to their external environments, search. has recently come under attack from several cor- In summary, Arthur proposes that evolutionary ners. The best-known example is surely Stephen change is determined by the interaction of natural Jay Gould, who argued throughout his career that selection with the structure of the variation offered evolution is not just about natural selection and ad- to it, played out within an enveloping matrix of aptation. A fuller view should also include a sub- historical contingency. stantial internal component that addresses how or- In arguing his case for the importance of devel- ganismic structure and development affect the opment for fully understanding the nature of evo- direction of evolutionary change. Gould summa- lutionary change, Arthur has managed to cram his rized his views in his massive book, The Structure

Downloaded from Brill.com09/24/2021 08:16:07PM via free access Contributions to Zoology, 74 (1/2) – 2005 211 of Evolutionary Theory (2002). Arthur is evidently more central position in . strongly influenced by Gould, who is one of the All these efforts attempt to promote “footnotes” dedicatees of Arthur’s book. This is demonstrated, in evolutionary theory into fully-fledged research for example, by both Gould’s and Arthur’s choices programs. to represent evolutionary theory with architectural metaphors. Odling-Smee et al. (2003) recently presented a References different perspective that also emphasizes how or- ganisms can affect the direction of their evolution Davidson E. 2001. Genomic regulatory systems. Development in the book Niche Construction: The Neglected and evolution. San Diego: Academic Press. Gerhart J, Kirschner M. 1997. Cells, embryos and evolution: Process in Evolution. Where Arthur and Gould ar- toward a cellular and developmental understanding of phe- gue for a greater role for the organism in providing notypic variation and evolutionary adaptability. Malden: the raw material for its own evolution by moving Blackwell. away from the interaction of the environment and Gould SJ. 2002. The structure of evolutionary theory. Cam- bridge: Harvard University Press the organism to produce adaptive evolutionary Minelli A. 2003. The development of animal form. , change, Odling-Smee et al. retain this focus, but morphology, and evolution. Cambridge: Cambridge Uni- would enhance the organism’s power to affect its versity Press. evolution by re-orienting the arrow of cause and Odling-Smee FJ, Laland KN, Feldman MW. 2003. Niche effect. Many organisms alter their immediate envi- construction: The neglected process in evolution. Princeton: Princeton University Press. ronments to create their own niches, and thus they Vermeij GJ. 2004. Nature: an economic history. Princeton: can both directly and indirectly affect the selection Princeton University Press. pressures acting on them, and thereby affect the Wilkins AS. 2002. The evolution of developmental pathways. direction of evolutionary change. Although this Sunderland: Sinauer. perspective is very different from that adopted by Arthur and Gould, it also places the organism in a Received: 18 October 2004

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