New Views of Life

Book Review scope (it seeks " an algorithm that connects phenotype New Views of Life to genotype "), while the level of detail is often very fine (there is a comparison of the anatomy of the echidna and platypus mammary gland at one point). excludes two essential aspects of biology that have Malden, Massachusetts: Blackwell Science, Inc. (1997). shaped the form of modern animals: genetics and physi-642 pp. $69.95. ology. Theodosius Dobzhansky said " Nothing in biology makes sense except in the light of evolution. " In their preface, the authors transform this unifying concept into The discovery of the evolutionarily conserved homeo-" Nothing in evolution makes sense except in the light box in 1983 marked the point at which our view of animal of cell biology. " This seems a shaky foundation on which evolution was permanently changed by the identification to build a new view of the relationship of animal species. of regulatory pathways that are shared by all animals. The forces that have shaped the forms of animals do not The realization that it is the modification of shared path-act on cells: they act on the organism as a physiological ways that results in the diversity of Darwin's " endless whole. By overlooking these dimensions, the book be-forms most beautiful and most wonderful " has de-longs in the old tradition of comparative embryology manded new ways of thinking about the relationships and takes little notice of the synthesis of evolution and of animals and about the mechanisms that allow related genetics fashioned by Dobzhansky and others. In terms molecules to generate so many different forms. of comparative embryology it is masterful, and the won-John Gerhart and Marc Kirschner take on this chal-der of life as presented here is in the diversity of forms lenge, and explore the relationships of all animals based that can be produced from variations in a small number on the properties of animal cells and comparative em-of ancestral pathways. bryology in Cells, Embryos, and Evolution. The contents The problems created by the evasion of natural selec-of the book fall into three sections. The first describes tion are illustrated in Chapter 8, " Axis Specification and the properties of cells that allow flexibility of function. Reproductive Strategies. " This chapter describes the The exploratory behavior of certain constituents of the extraordinary diversity of mechanisms of axis specifica-cell is nicely described; the authors point out, …