Red Queen's Hypothesis - The Paradox of Sex: The "cost" of Males

The Paradox of Sex: The "cost" of Males

For more details on this topic, see Evolution of sexual reproduction.

Science writer Matt Ridley popularized the term "the red queen" in connection with sexual selection in his 1993 book The Red Queen. In the book, Ridley 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 theory (Vicar of Bray) only showed adaptive benefit at the level of the species or group, not at the level of the gene (although, it must be added here that 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 theory that organisms are running cyclic 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.

Sex is an evolutionary puzzle. Sexual organisms must spend resources to find mates. In the case of sexual dimorphism, usually only one of the sexes, sometimes females sometimes males, contribute to the survival of their offspring. In such cases the only adaptive benefit of having another sex is the capability of sexual selection, by which organisms can improve their genotype. In this way, sexual reproduction can be highly inefficient.

For sex to be advantageous for these reasons requires constant selection for changing conditions. One factor that might cause this is the constant arms race between parasites and their hosts. Parasites generally evolve quickly because of their short life cycles. As they evolve, they attack their hosts in a variety of ways. Two consecutive generations might be faced with very different selective pressures. If this change is rapid enough, it might explain the persistence of sex.