Smith, John Maynard, and Eors Szathmary. The major transitions in evolution . Oxford University Press, 1997.
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This book is about the origin of life, of the genetic code, of cells, of sex, of multicellular organisms, of societies, and of language. Such a book is inevitably speculative, because it is an account of a series of unique events that happened a long time ago. But these are matters on which we must speculate. Why else would we study evolution? It is true that evolutionary biology has some practical relevance—for example, to animal breeding or to the origins of antibiotic resistance—but the real reason why we study it is that we are interested in origins. We want to know where we came from. Although the book is speculative, however, we think that it is a contribution to science, and not to fantasy. Speculation is constrained in two ways. First, each event must be explained in a way that is consistent with a general theory of evolutionary change, the theory of evolution by natural selection. Second, an adequate account of the origin of any system must explain the peculiarities of that system as it exists today: for example, a theory of the origin of the code should explain why it is a triplet code, why it is redundant, why similar codons specify chemically similar amino acids, and so on. In other words, theories about origins can be tested by looking at the present.