89–90 and nearly the same words in 1871, p. 243) by stating that these features were present in one sex and not the other, and that they either attracted mates or repelled

rivals. This was the genesis of the term sexual selection. Darwin needed this concept as a contrast to natural selection, in order to defuse a false argument of his detractors; he knew exactly what he was doing. Darwin cannot be ‘wrong’ about the definition of this concept, despite the protests or confusion of later authors, because he invented it, and his empirical basis for it is entirely selleck screening library valid; he was not ‘imprecise’ (paceCarranza, 2009). Myriad examples prove the presence of distinct, monosexual characters in species that are used to attract mates and repel rivals (Darwin, 1871; Andersson, 1994). Thus, the only possible definition of sexual selection requires sexual dimorphism (and not simply allometric sexual differences: Padian & Horner, 2010). To say this does not deny that many

factors are involved in the attraction of mates, the repulsion of rivals, success in mating and the differential production of Tyrosine Kinase Inhibitor Library cell line offspring. But sexual selection is only a small part of this, and Darwin was not trying to explain all aspects of mate recognition, attraction, competition and reproductive success. The notion that sexual selection involves more or different aspects than those defined by Darwin is an historical error of misinterpretation in the scholarly literature that has sadly become entrenched. But one cannot change the definition of a term at will. This only creates confusion and fosters misinterpretation

[consider the later misuses of Van Valen's (1973) original concept of the ‘Red Queen,’ which denoted the control of energy in an ecosystem by individual species]. We acknowledge that Darwin’s term is widely misused in the recent literature, and unfortunately, this has brought confusion to an extremely interesting and productive field. Futuyma (2009), whose textbooks have been the ne plus ultra of the field for many years, views sexual selection as a subtype of natural selection, and many biologists agree. There find more is an historical context for this misunderstanding. In the early 20th century, mathematical modelers of the Modern Synthesis needed to examine whether natural selection could be a viable force in populations (Mayr & Provine, 1980). The Darwin–Wallace hypothesis was that individuals that were more fit for their environments would wind up leaving their features to the next generation, in which they would be proportionally better represented. (That is a testable hypothesis that can be examined based on the presumed adaptive features of the individuals in question.) However, because these modelers could not quantify how well adapted a particular individual is, they modified the concept of ‘fitness’ by taking a shortcut. In their terms, the number of offspring would be an indirect measure of adaptive fitness.