Heritability of fluctuating asymmetry in a human twin sample: the effect of trait aggregation

Fluctuating asymmetry is thought to reflect developmental instability, which may in turn indicate genetically influenced fitness. Controversy surrounding these claims has centered on the extent to which fluctuating asymmetry is heritable. Most studies have estimated its heritability to be very low using single-trait measures. This study uses data from a human twin sample to demonstrate that the heritability estimate resulting from the aggregation of fluctuating asymmetry across multiple traits is non-zero. This is the case even when the estimates of fluctuating asymmetries of the individual traits do not differ significantly from 0.