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Nature 447, 261-262 (17 May 2007) | doi:10.1038/447261a; Published online 16 May 2007

The search for novelty

Wallace Arthur1

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Evo-devo is not the first attempt to understand how evolutionary innovations arise.

BOOK REVIEWEDFrom Embryology to Evo-Devo: A History of Developmental Evolution

edited by Manfred Laubichler & Jane Maienschein
MIT Press: 2007. 569 pp. $55 £33.95

Those of us lucky enough to have become, by whatever route, students of the interdisciplinary field of 'evo-devo' have a sense of history in the making — a feeling that a new synthesis is being born in biology, even if the birth is painfully slow. Indeed, many would say it is a rebirth: of comparative embryology in the age of the gene. The original birth, at the hands of Karl Ernst von Baer and Ernst Haeckel in the nineteenth century, and its late-twentieth-century equivalent, with Stephen Jay Gould's book Ontogeny and Phylogeny and the discovery of the homeobox, are connected by much intermediate work. This is made clear in From Embryology to Evo–Devo, edited by Manfred Laubichler and Jane Maienschein. The book tells the history of this work, which has not been told prominently enough before.

The search for novelty

PRIVATE COLLECTION/BRIDGEMAN ART LIBRARY

Prize Monet: finding the roots of evo-devo can be like searching for a needle in a haystack.

Both the book and its title derive from a pair of linked events: a seminar held at Woods Hole, Massachusetts, in 2001, and a workshop in 2002 organized by the Dibner Institute. These gatherings were mostly attended by historians of science, but also included a few practitioners of evo-devo. In the book's final chapter, one of the latter, Günter Wagner, describes this mix memorably as "birds and ornithologists together".

My first reaction to the book's title was that evo-devo has many roots, of which embryology is just one. But as Laubichler and Maienschein explain in their introductory chapter, "embryology and evo-devo are merely historical markers for the late nineteenth and the early twenty-first century, respectively". In fact, this first chapter is essential reading, as it outlines the structure of the book, which would otherwise be somewhat inscrutable. To my mind the flow is a bit odd: to have the first section defined by a block of historical time (the early twentieth century) but the other two sections defined in different (non-chronological) ways seems rather strained. So I view the book overall as something of a haystack, but it does contain many valuable needles.

My problem here is that a book of 16 chapters, some consisting of more than 50 pages (too long!), by assorted authors, is too big to do justice to in a short review. So I will concentrate on a few things that struck me as important recurring themes.

First, history is more complex than scientists often think, and consists of the interactions of a multitude of figures, not just those who show up repeatedly in the popular literature. I found the chapters on less-well-known figures particularly interesting, such as Alan Love's chapter on Dwight Davis and William Gregory. Although Davis was a morphologist and Gregory a palaeontologist, they were both interested in the origin of evolutionary novelties. And William Wimsatt provides an excellent comparison of the very different backgrounds of Rupert Riedl and Lancelot Law Whyte. He contrasts this with the similarities of their focal area, the 'internal' side of evolution (Riedl's concept of 'burden' and Whyte's 'internal selection').

Second, Haeckel's idea of recapitulation — the fleeting occurrence in embryos of 'advanced' animals of certain features of their ancestors — is not dead, despite many reports to the contrary. This point is made at some length by Frederick Churchill, who distinguishes between strong and weak versions of recapitulation. He notes that there are intermediates between them, and that they have changed over time, with the weak version becoming "even milder". Churchill concludes that only the strong version of recapitulation met "a natural death", and I think he is right. It all hinges on what is meant by 'recapitulation'. If it means 'repeats exactly' then of course it is false. On the other hand, if it means that the ontogenies of derived animals often retain features of the ontogeny of an extinct ancestor (as in the case of gill clefts in mammalian embryos), it is self-evidently true, but is more a statistical pattern than an inviolable law.

Third, and most important in my view, the origin of novelty is becoming one of the major themes of evo-devo. Attention is shifting from the retention of the old (as in recapitulation) to the creation of the new (be it an eye, a leg, a feather or even a whole body plan). Both the historical and the current importance of novelty emerge repeatedly in the book.

How do novelties arise? We can't yet agree on a definition for them, let alone answer this fundamental question. But we can see the nature of the challenge ahead. Wagner points out that there is a growing connection between microevolutionary (intraspecific) evo-devo and quantitative genetics (where intraspecific variation is analysed in terms of quantitative trait loci). This connection is a positive thing, although it is perhaps limited in scope because it may not solve what many perceive as the raison d'être of evo-devo. As Wagner says: "One of the main sources of intellectual excitement in devo-evo (sic) is the prospect of understanding major evolutionary transformations." Whether these end up being unique events or long-term accumulations of the mundane remains to be seen, but either answer will be exciting in its own way.

Overall, then, the book is a mixed bag, but contains many important contributions to the past, present and possible future of evo-devo. It is definitely a reference book rather than something to read from cover to cover. Its 'haystack' nature is off-putting at first, but the best strategy is to dive in (with the aid of the short introductory chapter) and see what you can find — including those needles that space has not permitted me to discuss.

  1. Wallace Arthur is European editor of the journal Evolution & Development. He is in the Department of Zoology, National University of Ireland, Galway, Ireland.

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