Owing its inspiration and title to On the Origin of Phlya, James W. Valentine's ambitious book synthesizes and applies the vast treasury of theory and research collected in the century and a half since Darwin's time. By investigating the origins of life's diversity, Valentine unlocks the mystery of the origin of phyla.

One of the twentieth century's most distinguished paleobiologists, Valentine here integrates data from molecular genetics, evolutionary developmental biology, embryology, comparative morphology, and paleontology into an analysis of interest to scholars from any of these fields. He begins by examining the sorts of evidence that can be gleaned from fossils, molecules, and morphology, then reviews and compares the basic morphology and development of animal phyla, emphasizing the important design elements found in the bodyplans of both living and extinct phyla. Finally, Valentine undertakes the monumental task of developing models to explain the origin and early diversification of animal phyla, as well as their later evolutionary patterns.

Truly a magnum opus, On the Origin of Phyla will take its place as one of the classic scientific texts of the twentieth century, affecting the work of paleontologists, morphologists, and developmental, molecular, and evolutionary biologists for decades to come.