Why sex evolution

Sexual reproduction in animals and plants is far more prevalent than asexual reproduction, and there is no dearth of hypotheses attempting to explain why. We confront this daily in the form of antimicrobial resistance. The host-parasite and host-pathogen arms race purports to explain the prevalence of sexual reproduction, yet there are over a dozen other hypotheses, including the proposition that sexual reproduction purges the genome of deleterious mutations. An equally daunting challenge is to understand, in terms of evolutionary logic, the jungle of diverse courtship and mating strategies that we find in nature. The phenotypic plasticity of sex determination in animals suggests that the central nervous system and reproductive tract may not reach the same endpoint on the continuum between our stereotypic male and female extremes.

The evolution of sexual reproduction is an adaptive feature which is common to almost all multi-cellular organisms and also some single-cellular organisms with many being incapable of reproducing asexually. Prior to the advent of sexual reproduction , the adaptation process whereby genes would change from one generation to the next genetic mutation happened very slowly and randomly. Sex evolved as an extremely efficient mechanism for producing variation, and this had the major advantage of enabling organisms to adapt to changing environments. Sex did, however, come with a cost. In reproducing asexually, no time nor energy needs to be expended in choosing a mate. And if the environment has not changed, then there may be little reason for variation, as the organism may already be well adapted.

W hat is sex for? When I regularly queried students at the beginning of my course in evolutionary biology, most responded that it was for reproducing. Reasonable enough, but wrong. In fact, lots of living things reproduce without sex: Asexual reproduction is found not only in many forms of archaea and bacteria, but also in numerous plants and protists, as well as in fully one half of all animal phyla.

This page has been archived and is no longer updated. Birds do it, and bees do it. Indeed, researchers estimate that over But why is sexual reproduction so commonplace? People typically employ several arguments in their efforts to explain the prevalence of sexual reproduction.