Mate Choice - Origins and History

Origins and History

Charles Darwin first expressed his ideas on sexual selection and mate choice in his book The Descent of Man, and Selection in Relation to Sex in 1871. He was perplexed by the elaborate ornamentation that males of some species have because they appeared to be detrimental to survival and have negative consequences for reproductive success. He proposed two explanations for the existence of such traits: these traits are useful in male-male combat or they are preferred by females. This article focuses on the latter. Darwin treated natural selection and sexual selection as two different topics although some scholars argue today that sexual selection is a form of natural selection.

The next advancement in the field of sexual selection took place decades later when R.A. Fisher first mentioned his ideas on the evolution of female preference through runaway selection in 1915. Fifteen years later, he expanded this theory in a book called The Genetical Theory of Natural Selection. There he described a scenario where feedback between mate preference and a trait results in elaborate characters such as the long tail of the male peacock (see Fisherian runaway).

Using Drosophila as a model, Angus J. Bateman presented experimental evidence that male reproductive success is limited by the number of mates obtained while female reproductive success is limited by the number of pregnancies that she can have in her lifetime. Thus, a female must be selective when choosing a mate because the quality of her offspring depends on it. Males must fight, in the form of intra-sexual competition, for the opportunity to mate because not all males will be chosen by females. This became known as Bateman's principle and although this was a major finding that added to the work of Darwin and Fisher, it was overlooked until George C. Williams emphasized its importance in the 1960s and 1970s.

Soon after Williams' revival of the subject, Robert L. Trivers presented his parental investment theory. Parental investment was defined by Trivers as any investment made by the parent that benefits his or her current offspring at the cost of investment in future offspring. These investments include the costs of producing gametes as well as any other care or efforts that they will provide after birth or hatching. Reformulating Bateman's ideas, Trivers argued that the sex that exhibits less parental investment (not necessarily the male) will have to compete for mating opportunities with the sex that invests more. The differences in levels of parental investment create the condition that favors mating biases.