It has been applied to understanding both economic and political behaviour, but perhaps its greatest success has come in the field of evolutionary biology. In evolutionary systems however, players become phenotypes with predictable behaviours and the criterion of self-interest is replaced by Darwinian fitness. An ESS is a strategy which if adopted by most individuals of a population , cannot be invaded by another strategy that is initially rare. The predictions of these models are compared with observations. The evolution of genetic systems is one of the most interesting and fundamental questions in evolutionary biology.
Asexuality is thought to be the most primitive state.
In present taxa, obligate asexual reproduction is most typical of parthenogens. We discuss evidence and criticisms of each of these hypotheses.