SOME PROBLEMS WITH THE EVOLUTION OF SEX

Abstract

During the last ten years John Maynard Smith and colleagues at the University of Sussex have reexplored some old models and developed new models for a variety of problems associated with genetic systems. These contributions have been collected together, expanded with some history and natural history, and presented as The Evolution of Sex. The first chapter provides a particularly lucid introduction to the problem beginning with the cost of producing males and proceeding to a discussion of the various long and short term advantages which have been attributed to sex and recombination. Maynard Smith also sketches out a possible model of the origin of sex, but emphasizes that the primary problem of the book is the maintenance of sex. Subsequent chapters (ten) follow the format of an introduction to the problem, the presentation of a model, and the discussion of selected biological observations. The major models or problems considered in these chapters are the flux of favorable or unfavorable mutations, parthenogenesis and evolutionary potential, selection for changes in the rate of recombination, sib-competition and unpredictable environments, recombination and hitch-hiking, hermaphroditism, anisogamy and sex ratio, sexual selection and optimal mutation rates. Maynard Smith's forte of making the steps by which conclusions emerge from assumptions followable for individuals without sophisticated knowledge is well represented in these chapters. Despite the positive features of the clear statement of the problem and understandable presentation of the models, many readers may feel that not much progress in understanding the origin and maintenance of sex has been made. This major fault is admitted by the author in the preface where he states, my mind is not made up and is not clear to me whether the short term selective forces I discuss are sufficient to account for the facts, or whether models of a qualitatively different kind are needed. While it is frequently more satisfying to finish a book with a focused theme, it is not just the lack of a theme which is disconcerting. The really discouraging thing about this book is that the diversity of the assumptions of the models and the flexible quantitative aspects of their predictions seem to offer no hope of