The grand scheme of life

Oxford University Press, 1998. £18.99 hbk (266 pages)ISBN 0 19 8502567The Burgess Shale has come to embody the relevance of paleontology for contemporary biology. This small quarry, located high in the Rocky Mountains of British Columbia, is packed with exquisite fossils of animals that flourished during the middle of the Cambrian era. The surprising diversity of animals, and outright weirdness of many of them, has exerted a strong influence on attempts to understand the early evolutionary history of animals. There is little dispute among paleontologists about the historical impact of these fossils, nor about their continuing importance. The same, however, cannot be said about interpretations.Simon Conway Morris, who has contributed enormously to our understanding of the Burgess Shale, has produced an appealing book on the subject for non-specialists. The comfortable narrative and engaging cover art might lead one to imagine that the purpose of this book is simply to provide an accessible introduction to the Burgess Shale and to the diversification of animals in general. And indeed, it accomplishes this goal admirably well. But the real motivation for the book, articulated in the preface and rarely far beneath the surface elsewhere, is the author's sharp disagreement with the interpretations that Stephen Gould placed on the Burgess Shale fauna in his book Wonderful Life1xWonderful Life. Gould, S. See all References. Crucible of Creation is an attempt to set the record straight.The crux of the disagreement between Gould and Conway Morris concerns the relative importance of adaptation and contingency in evolution. Gould has forcefully argued that chance events have left a stronger imprint on the history of life than adaptation, while Conway Morris regards contingency as inevitable but trivial compared with natural selection. This disagreement lies at the heart of several more specific disputes, whose consideration takes up about a third of the book. For the most part, Conway Morris's arguments ring true. Compared with Wonderful Life, Crucible of Creation is more succinct, more engaged with evidence, and less polished rhetorically.It might seem odd that fossils from one small locality, no matter how exciting, should lie at the center of a fierce debate about such broad issues in evolutionary biology. The reason is that animals burst into the fossil record in astonishing profusion during the Cambrian, seemingly from nowhere. Increasingly precise radiometric dating and new fossil discoveries have only sharpened the suddenness and scope of this biological revolution. The magnitude of this change in Earth's biota demands an explanation. Although many hypotheses have been proposed, the general consensus is that none is wholly convincing. Conway Morris doesn't attempt to provide an explanation for the Cambrian revolution, but he does weigh in with some interesting opinions.Somewhat surprisingly, Crucible of Creation devotes relatively little attention to the importance of molecular and genetic data in understanding the early evolution of animals. The famous similarities in the genetic basis for the development of diverse animals receive a passing nod, but their implications are barely discussed. The same is true of recent analyses that suggest deep pre-Cambrian divergence times among animal phyla based on rates of molecular evolution. The enormous potential of sequence data for resolving phylogenetic relationships among animal phyla, and the sorry state of progress in this area, receive even less consideration.An intriguing (and surprising) feature of Conway Morris's book is his concern for the spiritual and moral place of humans in the grand scheme of life. Gould is, of course, also concerned with morality. But where Gould draws upon ideology for inspiration, Conway Morris looks directly to the history of the world we live in. The uniqueness of humans as a species within that long, rich history motivates a sprinkling of comments that deserve to be read and pondered.In a sense, then, this book delivers more than it promises. While it is an engaging introduction to the early evolution of animals from a paleontological perspective, it also provides an absorbing window into some of the most lively debates in evolutionary biology as a whole. This is a busy and exciting time for research on the early diversification of animals, and I hope that it won't be too long before Conway Morris is at work on a sequel.