On the Origin of Phyla

Rating:
Summary: An important work, but hard going
Review: I am a biologist yet found this book a hard study. No, I didn't READ it, I studied it. That's what is required. My little corner of biology is not evolutionary biology, so this book was a bit off my beaten track. For those with the determination, this is a very rewarding work, and may become a classic. It lacks a good glossary; the one it has seems to have been thrown together as an afterthought. The illustrations could benefit from serious upgrading. Yet with these minor faults, I still rate this book as 5 stars. A truly marvelous work.

Rating:
Summary: Destined to be a Classic.
Review: In his important book `The Crucible of Creation', Simon Conway Morris stated: `In my opinion there is no really good book by a single author on the early evolution of animals...' Although I used to think that Morris' book was in fact the best, the definitive book on the origin of the animals has arrived.

James W. Valentine, one of the world's greatest paleobiologist has produced a synthesis of the most modern knowledge on the origin end early evolution of the animals. This synthesis could only have been achieved in the last few years, because of the recent advances in the relevant fields. This book makes use of the latest results from molecular phylogenetics (the study of the relationships between animal groups), paleontology and genetics (especially in the field of development).

For a book of this depth, it is very clear. Valentine's writing style is as informal as possible, and the book is structured in short sections with incisive titles. Most technical terms are defined in the text and also in a glossary, at the end of the book. The book is richly illustrated with very clear line drawings. (No color plates of Anomalocarises devouring hapless trilobites, however!)

I would suggest getting the hardcover edition, because an eventual paperback will probably have reduced page size, which will reduce the clarity of the illustrations and diagrams. As it is, the book is very pleasant to read: the page layout is not too crowded, with large margins. Even the paper (acid-free) is very pleasing to the eyes, not being glossy, or too white. Lovers of beautiful books should get this volume, even if they are only marginally interested in biology and evolution!

In the following I will give the table of contents of the book, with a few comments (and quotations).

Part One: Evidence of the Origins of Metazoan Phyla.

Chapter 1: The Nature of Phyla. Phyla Are Morphologically Based Branches of the Tree of Life.

Chapter 2: Design Elements in the Bodyplans of Phyla.

Chapter 3: Development and Bodyplans. The Genetics of Development. The English Language and Genomes Both Have Combinatorial, Hierarchical Structures.

Chapter 4: Morphological and Molecular Phylogenies. The relationships between groups of animal derived from observations and from genetic data. The conclusion, mostly based on rRNA data, divides the Protostomes into Lophotrochozoa (Mollusca, Annelida, Platyhelminthes (!), Brachiopoda, etc.), Ecdysozoa (Arthropoda, Nematoda (!), Priapulida, etc.) and Paracoelomates. The Deuterostomes remain, but only include the Chordata (and related Phyla) and the Echinodermata. This division is the base of the discussion in Part two.

Chapter 5: The Fossil Record. Knowledge of Neoproterozoic and Cambrian Faunas Has Greatly Increased in Recent Decades.

Part Two: The Metazoan Phyla. Both living and fossil forms are discussed.

Chapter 6: Prebilaterians and Earliest Crown Bilaterians.

Chapter 7: Protostomes: The Ecdysozoa.

Chapter 8: Protostomes: Lophotrochozoa 1: Eutrochozoans.

Chapter 9: Protostomes: Lophotrochozoa 2: Lophophorates.

Chapter 10: Protostomes: Paracoelomates.

Chapter 11: Deuterostomes.

Part Three: Evolution of the Phyla.

Chapter 12: Phanerozoic History of Phyla.

Chapter 13: Metazoan Evolution during the Prelude to the Cambrian Explosion. Argues that molecular and fossil evidence indicates that much of the early evolution of the bilaterians occurred in the benthos (on the bottom), rather than in the plankton.

Chapter 14: Metazoan Evolution during the Cambrian Explosion and Its Aftermath. How to explain the Cambrian explosion? Still no completely satisfactory answer!

In conclusion, a work of immense scope. A work that could not have been written ten years ago. Despite the remaining problems, the main conclusions of this book will probably not be overturned, because the molecular and fossil lines of evidence are converging.