ABSTRACT
Sex is the queen of problems in evolutionary biology. Perhaps no other natural phenomenon has aroused so much interest; certainly none has sowed as much confusion. The insights of Darwin and Mendel, which have illuminated so many mysteries, have so far failed to shed more than a dim and wavering light on the central mystery of sexuality, emphasizing its obscurity by its very isolation. No doubt the roots of this difficulty lie very deep. There are problems which are not excessively difficult to solve, but which are exceedingly difficult to see; not because they are obscure or trivial, but because they are painted so large in the foreground of the canvas that the eye glides over them, taking them as the givens which can be used to solve other and more important problems whilst not themselves requiring solution. After more than a century of Darwinism, during which time most of the conspicuous details in the background have yielded their secrets, we are too close to the canvas to appreciate that large areas in the foreground are still uncharted, still less explored. It seems that some of the most fundamental questions in evolutionary biology have scarcely ever been asked, and consequently still await an answer. Every student knows that homologous chromosomes usually segregate randomly during the division of the nucleus; no professor knows why. Every layman knows that all the familiar animals and plants have two sexes, but never more; few scientists have thought to ask, and none have succeeded in understanding, why there should not often be three or many sexes, as there are in some ciliates and fungi. The largest and least ignorable and most obdurate of these questions is, why sex? Or, to put this more technically, what is the functional significance of sexuality, which leads to its maintenance under natural selection in biological populations?
