From Angus Martin
I am puzzled as to why Guy Cox finds it puzzling that we are not hermaphroditic (10 January, p 30). There are good reasons for the evolution of dimorphism in gametes, resulting in big, less mobile ones and small, mobile ones. When that happened, selection for different behaviour on the part of the “females” that produce the big gametes and the “males” that produce the small ones began to operate.
Co-occurrence of the two kinds of gamete production within one body precludes the development of such differences. No wonder simultaneous hermaphroditism is the rare exception rather than the rule among vertebrates.
Camberwell, Victoria, Australia
