ABSTRACT
The egg carries only the X chromosome and is therefore wholly female while spermatozoa carry either the male Y chromosome or the female X chromosome and will thus determine the sex of the little creature their combined chromosomes will create. Sex differentiation begins with the Y chromosome, a stumpy little creature that evolved from a pair of autosomes in vertebrates many millions of years ago. Transsexuals are persons who feel strongly that they inhabit the body of the wrong sex. Transsexuals reveal just how complicated is the process of sexing what all mammals are prior to that momentous sixth week—undifferentiated hermaphrodites. The uniquely human pattern of mating probably has a lot to do with the evolution of love. Compared to humans, most mammalian species are extraordinarily individualistic. All the theoretical speculations about the origins of love do not rule one another out; all of them doubtless had some role to play in the evolution of love.
