title: Left-handedness and male-male competition: insights from fighting and hormonal data.
abstract: Male-male competition can shape some behavioral or morphological traits of males. Here we investigate if this competition could play a role in the persistence of the polymorphism of handedness in human populations. A negative frequency-dependent selection mechanism has been hypothesized, based on the fact that left-handed men may benefit from a "surprise" advantage during fighting interactions because they are rare in human populations. This advantage may thereby enhance the probability of survival of left- handed men and/or their reproductive success through an increase in social status. In this study, we first explored the association between hand preference and lifetime fighting behavior in a population of 1,161 French men. No effect of hand preference on the probability of fighting was detected, suggesting that the innate propensity to fight does not differ between left- and right-handers. However, among men who had been involved in at least one fight during their lifetime, left-handers reported significantly more fights than right-handers. To explore the biological basis of this behavior, we also investigated the testosterone concentration in saliva samples from 64 French university students. Consistent with frequencies of fights, we found a significantly higher average testosterone concentration in left-handers than in right-handers. We suggest that these behavioral and hormonal differences may be acquired throughout life due to previous experiences in a social context and may favor the persistence of left-handers in humans.
authors.affiliation: CNRS, Institute of Evolutionary Sciences, Université de Montpellier 2, Montpellier cedex 5, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Faurie
authors.forename: Violaine
authors.initials: V
authors.lastname: Llaurens
authors.forename: Alexandra
authors.initials: A
authors.lastname: Alvergne
authors.forename: Marcel
authors.initials: M
authors.lastname: Goldberg
authors.forename: Marie
authors.initials: M
authors.lastname: Zins
authors.forename: Michel
authors.initials: M
authors.lastname: Raymond
mesh_terms: D000328:Adult; D000374:Aggression / Q000502:physiology*; D015331:Cohort Studies; D003163:Competitive Behavior / Q000502:physiology*; D005602:France; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012463:Saliva / Q000378:metabolism; D013334:Students; D011795:Surveys and Questionnaires; D013739:Testosterone / Q000378:metabolism*; D055815:Young Adult
chemical_list: D013739:Testosterone