ABSTRACT
It is self-evident that the sexual dimorphism of human external genitalia is so marked that sex assignment at birth can usually be done at a cursory glance. More than 2000 years ago Aristotle thought that the sex of children was determined by the temperature of sperm at the time of copulation. Sex in some reptilian species is, indeed, determined by the temperature at which fertilized eggs are incubated. This is not the case in the human in which sex is determined by a complex (and still incompletely understood) interplay of genes and hormones.
