FREQUENCY-DEPENDENT MAINTENANCE OF LEFT-HANDEDNESS IN HUMANS

The percentage (10-13%) of left handedness in humans has apparently no t changed since the Neolithic. Left handedness is heritable and appear s to be repeatedly associated with some reduced fitness components; th e persistence of left handedness implies that left handers have a fitn ess advantage in some situations. We propose that left handers have a frequency-dependent advantage in fights and for that reason a fitness advantage. To test this hypothesis, left handedness frequencies in the general population and in sporting individuals (both students and the sporting elite) have been compared, as sporting performance is likely to be a good indicator of fighting abilities. The higher proportion o f left-handed individuals in interactive sports (reflecting some fight ing elements), reaching 50% in some sports categories, but not in noni nteractive sports, is consistent with the fighting hypothesis. The gre ater frequency of left handedness in males than in females is also con sistent with this hypothesis, as male-male fights are universally more frequent than other combinations. The frequency-dependent advantage i n fights of left handers might explain the stability of left handednes s.