Hanna Kokko (University of Zürich)
Abstract. The evolution of sex, and its subsequent high prevalence in nature, is one of the great mysteries of life. The main reason, the so-called "twofold cost of sex," has something to do with male production: the cost does not exist in the same form in isogamous organisms that lack males and females. Such organisms, however, can still experience e.g., costs of mate-finding. The differences in costs are relevant because sex does not always coincide with there being two sexes in a population: ancient sex was neither obligatory nor did it feature a male-female dimorphism. I will spend some time discussing how this impacts the evolution of sex, and how the rules of sex change once there are males (a specialized morph that finds it more difficult to switch to asexual reproduction than what is possible for females).