Folio Books: Review of Invertebrate Zoology by Ruppert and Barnes

Invertebrate Zoology

by Edward E. Ruppert and Robert D. Barnes

Sixth Edition, Harcourt Brace, 1994

1054 pages plus glossary and index.

From the confident way people talk about one animal having evolved from another, you would never guess that current theories of evolution rest on uncertain foundations and are, in fact, beset by controversy. This fine textbook clarifies the origins of the controversies, though that is not its prime purpose.

Over a million species of animals have been described and of these about ninety-five per cent are invertebrates. Their diversity, beauty and complexity is astonishing, their forms and life cycles often bizarre. This book explains the principles underlying their classification and describes the characteristics and life cycles of broad groups, relating structure to function and ecological niche with a satisfactory amount of detail. The language is clear, sober, logical and unambiguous. The text is supplemented with hundreds of line drawings, diagrams and photos of these most startling creatures, and is well referenced.

Questions which perplex evolutionists, such as which organism or group of organisms came first or is more primitive than another, loom large in the case of invertebrates -- there are so many species, and they are so tiny, it should be possible to lay them all out in a line, or at least in a bush. From reading this book it is evident that nothing so neat is possible, not even at the simplest levels of life. Not, of course, that any level of life is simple, a fact that comes through strongly here. Some animals have evolved by becoming "simpler", for instance. Some very small organisms may be more advanced than bigger ones. New technologies such as transmission electron microscopy and RNA sequencing continue to reveal unsuspected relationships and lineages. When you get right down to it, down to the most primitive metazoans, it turns out that experts differ, sometimes passionately, in their ideas of how these organisms evolved. Biologists are forced to assume something that they would prefer not to assume; that is to say, that a landmark process, signalling a significant evolutionary divergence, would have had to evolve independently more than once. The most widely-accepted theory presupposes that radial cleavage of cells (as opposed to spiral cleavage, which was a later development) evolved separately on two occasions. The book sets out the current thinking and competing hypotheses in an even-handed way in the last chapter.

I bought the book in the hope that contradictions and puzzles in evolution theory might be better understood through invertebrates. (Besides, in tropical Trinidad one is confronted daily by dozens of them and I wanted some kind of reference.) Popular science writers tend to give the impression that evolution is all worked out and that gradual adaptation as its prime mechanism is firmly proved. This is not the case. What is at issue is not the fact of evolution, nor even of natural selection, but the mechanisms leading to the appearance of new species. Gradual adaptation, alone or mostly? If not, then what? While this book does not address the question directly, it points out many areas of disagreement and doubt. It presents the world of invertebrates with scientific restraint and accuracy, and in the process, oddly enough, by describing the diverse multitude of marvellous, bizarre, ingenious living creatures around us, it restores to us the sheer wonder of life on earth, which was in danger of being torn away by torrents of genes. Finally, it identifies the little difficulty at the very root of evolution theory.

This is academic rather than popular science but it is so clearly written and illustrated that anyone who has read widely in the popular literature would have no difficulty with it and might even find it a pleasure.

Ruppert and Barnes, Invertebrate Zoology, Sixth Edition is listed as back-ordered on Amazon, available in 3 to 5 weeks. A check with the publisher (Harcourt Brace College Publishers, Orlando, Florida) reveals that copies are still available. A reprint is due in September. Hardcover US$79.95, not available in paperback.

M.A., August 8, 1997

Harcourt Brace's Web site.