The Red Queen's Hypothesis, Red Queen, "Red Queen's race" or "Red Queen Effect" is an evolutionary hypothesis. The term is taken from the Red Queen's race in Lewis Carroll's Through the Looking-Glass. The Red Queen said, "It takes all the running you can do, to keep in the same place." The Red Queen Principle can be stated thus:
- "For an evolutionary system, continuing development is needed just in order to maintain its fitness relative to the systems it is co-evolving with."
The hypothesis is intended to explain two different phenomena: the advantage of sexual reproduction at the level of individuals, and the constant evolutionary arms race between competing species. In the first (microevolutionary) version, by making every individual an experiment when mixing mother's and father's genes, sexual reproduction may allow a species to evolve quickly just to hold onto the ecological niche that it already occupies in the ecosystem. In the second (macroevolutionary) version, the probability of extinction for groups (usually families) of organisms is hypothesized to be constant within the group and random among groups.
- The paradox of sex — the "cost" of males
Science writer Matt Ridley popularized the term "the red queen" in connection with sexual selection in his 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. In most sexual species, males make up half the population, yet they bear no offspring directly and generally contribute little to the survival of offspring. In fact, in some species, such as lions, males pose a positive threat to live young fathered by other males (although this could be viewed as a manifestation of Richard Dawkins' so-called selfish gene, whose 'goal' is to reproduce itself, which may as a consequence suppress the reproduction of other genes). In addition, males and females must spend resources to attract and compete for mates. Sexual selection also can favor traits that reduce the fitness of an organism, such as brightly colored plumage in birds of paradise that increases the likelihood for an individual to be noticed by both predators and potential mates (see the handicap principle for more on this). Thus, sexual reproduction can be highly inefficient.
One possible explanation for the fact that nearly all vertebrates are sexual is that sex increases the rate at which adaptation can occur. This is for two reasons. Firstly, if an advantageous mutation occurs in an asexual line, it is impossible for that mutation to spread without wiping out all other lines, which may have different advantageous mutations of their own. Secondly, it mixes up alleles. Some instances of genetic variation might be advantageous only when paired with other mutations, and sex increases the likelihood that such pairings will occur. Also, in asexually reproducing organisms, especially parthenogenetic organisms, mutations conferring an advantageous allele will have to occur twice, before the advantageous allele becomes fixed in the population, resulting in a longer phase where the heterozygote for the disadvantageous allele (relative to the new advantageous allele) is fixed in the population.
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.
- See also
- Evolutionary arms race
- Chaos theory
- Punctuated equilibrium
- Self-organized criticality
Read more about this topic: Red Queen (Through The Looking-Glass), Adaptive Uses Outside The Arts
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