We investigated whether fluctuating asymmetry (FA) is related to the expression of romantic jealousy. The mate retention hypothesis suggests that romantic jealousy functions to prevent philandering, so one's mate value, relative to rivals, may be a factor modulating jealousy. FA was used as a measure of mate value, and we found, as predicted, that asymmetrical individuals are significantly more jealous in mating contexts, but not in nonromantic contexts.
Fluctuating asymmetry (FA) refers to deviations from perfect bilateral symmetry in morphological traits (Van Valen, 1962). Random errors in development can cause disturbances in cell division, differentiation, and growth, resulting in asymmetries in bilateral structures. “Developmental stability” (DS) refers to the capacity to withstand such developmental noise and attain the phenotypic “design” that selection has favoured, so low FA can be considered an index of high DS. FA has been linked to various measures of phenotypic quality and fitness (see Møller & Swaddle, 1997 for review), and is exacerbated by developmental stressors including pathogens, mutagens, and homozygosity (but see Kark, Safriel, Tabarroni, & Randi, 2001). In humans, low levels of FA are reportedly associated with attractiveness Grammer & Thornhill, 1994, Hume & Montgomerie, 2001, Rikowski & Grammer, 1999 and Scheib et al., 1999 and good health (Reilly et al., 2001, Shackelford & Larsen, 1997, Shackelford & Larsen, 1999 and Waynforth, 1998; but see Rhodes et al., 2001), so mating with low-FA individuals may provide both phenotypic and genetic benefits.
