text: The Red Queen hypothesis is used independently by Hartung and Bell to explain the evolution of sex, by John Jaenike to explain the maintenance of sex and W. D. Hamilton to explain the role of sex in response to parasites. In all cases, sexual reproduction confers species variability and a faster generational response to selection by making offspring genetically unique. Sexual species are able to improve their genotype in changing conditions. Consequently, co-evolutionary interactions, between host and parasite, for example, may select for sexual reproduction in hosts in order to reduce the risk of infection. Oscillations in genotype frequencies are observed between parasites and hosts in an antagonistic coevolutionary way without necessitating changes to the phenotype. In multi-host and multi-parasite coevolution, the Red Queen dynamics could affect what host and parasite types will become dominant or rare. Science writer Matt Ridley popularized the term in connection with sexual selection in his 1993 book The Red Queen, in which he discussed the debate in theoretical biology over the adaptive benefit of sexual reproduction to those species in which it appears. The connection of the Red Queen to this debate arises from the fact that the traditionally accepted Vicar of Bray hypothesis only showed adaptive benefit at the level of the species or group, not at the level of the gene (although the protean "Vicar of Bray" adaptation is very useful to some species that belong to the lower levels of the food chain). By contrast, a Red-Queen-type thesis suggesting that organisms are running  arms races with their parasites can explain the utility of sexual reproduction at the level of the gene by positing that the role of sex is to preserve genes that are currently disadvantageous, but that will become advantageous against the background of a likely future population of parasites.