Handedness, homicide and negative frequency-dependent selection.
Humans exhibit hand preference for most manual activities in which they are specialized. Right- and left-handers have coexisted at least since the Upper Palaeolithic, and left-handers are in the minority in all human populations. The persistence of the polymorphism of handedness is a puzzle because this trait is substantially heritable and several fitness costs are associated with left-handedness. Some countervailing benefit is required to maintain the polymorphism. Left-handers may have a frequency-dependent advantage in fights--the advantage being greater when their frequency is lower. Sports data from Western societies are consistent with this prediction. Here, we show that the frequency of left-handers is strongly and positively correlated with the rate of homicides across traditional societies. It ranges from 3% in the most pacifistic societies, to 27% in the most violent and warlike. This finding is consistent with a frequency-dependent selection mechanism maintaining left-handedness in these societies.
Faurie
Charlotte
C
Genetics of Adaptation, Institute of Evolutionary Sciences (UMR CNRS 5554), University Montpellier II, CC 065, 34095 Montpellier 5, France. faurie@isem.univ-montp2.fr
Raymond
Michel
M
D005006:Ethnicity; D007839:Functional Laterality / Q000502:physiology*; D006708:Homicide / Q000706:statistics & numerical data*; D006801:Humans; D012641:Selection, Genetic