Spring 2007

Challenging Darwin’s theory of sexual selection

Joan Elizabeth Roughgarden

Joan Roughgarden, a Fellow of the American Academy since 1993, is professor of biological sciences and geophysics at Stanford University. Her publications include “Theory of Population Genetics and Evolutionary Ecology” (1979), “Anolis Lizards of the Caribbean” (1995), “Evolution's Rainbow” (2004), which won a Stonewall Prize for nonfiction from the American Library Association, and, most recently, “Evolution and Christian Faith: Reflections of an Evolutionary Biologist” (2006).

May a biologist in these polarized times dare suggest that Darwin is a bit wrong about anything? Even worse, does a biologist risk insult, ridicule, anger, and intimidation to suggest that Darwin is incorrect on a big issue? We have a test case before us. Darwin appears completely mistaken in his theory of sex roles, a subject called the ‘theory of sexual selection.’1

In his 1871 book The Descent of Man, and Selection in Relation to Sex, Darwin wrote: “Males of almost all animals have stronger passions than females,” and “the female . . . with the rarest of exceptions is less eager than the male . . . she is coy.”2 Notice that the exceptions are dismissed as empirically insignificant (“almost all,” “rarest of exceptions”), so that, for all practical purposes, males are universally “passionate” and females collectively “coy.”

To explain this claim, Darwin considered the joint mechanisms of male-male competition and female choice. He envisioned that males compete for access to females, while females choose superior males on the basis of success in male-male competition and/or perceived beauty. In effect, through their choice of mates, females breed their offspring to have their mates’ desirable traits, “just as man can improve the breed of his game-cocks by the selection of those birds which are victorious in the cockpit.” Another example: “Many female progenitors of the peacock must [have], by the continued preference of the most beautiful males, rendered the peacock the most splendid of living birds.” From a masculinist perspective, acquisition of females is a just reward for victory in male-male combat. From a maternalist perspective, the duty of females is to bed the victors, thus endowing their offspring with valuable traits.

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  • 1J. Roughgarden, Evolution’s Rainbow: Diversity, Gender and Sexuality in Nature and People (Berkeley: University of California Press, 2004).
  • 2C. Darwin, The Descent of Man, and Selection in Relation to Sex, facsimile edition (Princeton, N.J.: Princeton University Press, 1871).
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