The origin and evolution of sexual reproduction up to the evolution of the male-female phenomenon

Abstract

Sexual reproduction is a composite, not a singular, phenomenon and as such can be subdivided into a number of componentsi.e. fusion, recombination, fission, and the male-female phenomenon. These components can evolve independently, though any evolutionary change in one component is likely to influence the future evolution of the other components. The ambiguity that surrounds the term ‘sex’ due to a failure to recognise the composite nature of sexual reproduction has led to considerable confusion in past discussions of the evolution of the phenomenon. This paper considers the possible chronological interaction of the components of sexual reproduction both with each other and with the sequence of selective pressures that seem likely to have acted. This chronological approach is used to consider: the origin of sexual reproduction; the evolution of sexual reproduction in the common ancestor of the procaryotes and eucaryotes; the modification of the ancestral system in the procaryote line following the procaryote-eucaryote dichotomy; and the modification of the ancestral system in the eucaryote line up to the origin of the male-female phenomenon.