Female preference for symmetrical males as a by-product of selection for mate recognition.

Fluctuating asymmetry (FA) refers to the random, stress-induced deviations from perfect symmetry that develop during the growth of bilaterally symmetrical traits. Individual differences in the level of FA may influence mate choice: in a number of species, females prefer to mate with males that have more symmetrical sexual ornaments. As the degree of FA has been shown to reflect the ability of individuals to cope with a wide variety of environmental stresses, it has been suggested that mating preferences for symmetry evolve for adaptive reasons, because the degree of FA provides honest information about male quality. Here I use simple, artificial neural networks to show that such preferences are likely to arise in the absence of any link between symmetry and quality, as a by-product of selection for mate recognition.