High in the Canadian Rockies is a small limestone quarry formed 530 million years ago called the Burgess Shale. It hold the remains of an ancient sea where dozens of strange creatures lived -a forgotten corner of evolution preserved in awesome detail. In this book Stephen Jay Gould explores what the Burgess Shale tells us about evolution and the nature of history.

The book has three major aims. It is, first and foremost, a chronicle of the intense intellectual drama behind the outward serenity of this reinterpretation. Second, and by unavoidable implication, it is a statement about the nature of history and the awesome improbability of human evolution. As a third theme, I grapple with the enigma of why such a fundamental program of research has been permitted to pass so invisibly before the public gaze. Why is Opabinia, key animal in a new view of life, not a household name in all domiciles that care about the riddles of existence?

Harry Whittington and his colleagues have shown that most Burgess organisms do not belong to familiar groups, and that the creatures from this single quarry in British Columbia probably exceed, in anatomical range, the entire spectrum of invertebrate life in today’s oceans. Some fifteen to twenty Burgess species cannot be allied with any known group, and should probably be classified as separate phyla.

Magnify some of them beyond the few centimeters of their actual size, and you are on the set of a science-fiction film; one particularly arresting creature has been formally named Hallucigenia. For species that can be classified within known phyla, Burgess anatomy far exceeds the modern range. The Burgess Shale includes, for example, early representatives of all four major kinds of arthropods, the dominant animals on earth today-the trilobites (now extinct), the crustaceans (including lobsters, crabs, and shrimp), the chelicerates (including spiders and scorpions), and the uniramians (including insects).

But the Burgess Shale also contains some twenty to thirty kinds of arthropods that cannot be placed in any modern group. Consider the magnitude of this difference: taxonomists have described almost a million species of arthropods, and all fit into four major groups; one quarry in British Columbia, representing the first explosion of multicellular life, reveals more than twenty additional arthropod designs! The history of life is a story of massive removal followed by differentiation within a few surviving stocks, not the conventional tale of steadily increasing excellence, complexity and diversity.