Historical sweep

It was noted in the opening chapter that the reproductive musings of the ancient Greeks unwittingly contained some elements of truth, for example those concerning the left–right differences between gonadal size and type in hermaphrodites, but little real progress in understanding the formation and function of the sexual organs took place until growth of the Italian medical schools in the late Middle Ages; even then, progress was slow. The dissecting room paved the way to ever more accurate descriptions and illustrations of reproductive tissues but, in terms of explaining the mysteries of generation, powerful imagination was an invariable substitute for solid facts. Only with the advent of reasonable quality microscopes were the respective gametes and their gonadal origins discovered, these giving way to general descriptions of the process of fertilisation and eventually to a visualisation of mammalian chromosomes. Although the dual nature of embryonic duct systems had been more or less appreciated since the studies of Caspar Wolff and Johannes Müller and also, in due course, the dual potential of the embryonic gonads, a rational understanding of the decisive elements in mammalian sex determination had to await the technique of karyotyping 150 years later. In effect, it was the crucial clinical evidence presented during 1959 on the involvement of the Y chromosome in imposing the condition of maleness irrespective of the number of X chromosomes, coupled with developments in the tender young discipline of molecular biology, that enabled today's grasp at the level of individual genes.