Sex and genders: are there more than two?
The one-celled, slipper-shaped animal we know as Paramecium can live alone, dividing into two when it is time to reproduce. When opportunity allows, a Paramecium will pair with another Paramecium and mate, trading substance of their selves. But pairing is not haphazard. There are over half a dozen different “mating types” of paramecia, and only certain pairings are possible. Sex, in paramecia, comes in more than two distinct forms. Are we humans more like paramecia than we thought?