Socio-economic status and handedness in two large cohorts of French adults

Left-and right-handers have coexisted since the Palaeolithic age. Hand preference is heritable. Moreover, there is extensive evidence of an association between left-handedness and several fitness costs. In this context, the persistence of the polymorphism is interesting. Here, we explore the associations between socioeconomic status and handedness, analysing data from two large cohorts of adult men and women. Such associations are relevant to an evolutionary approach, as the socioeconomic and the reproductive value are related. Our results partly support the hypothesis that left-handers have a socio-economic status advantage, countervailing the health issues. Although the models explain a small proportion of the variance observed, the frequency of left-handedness is significantly higher: (1) among women of higher educational level; (2) among categories of higher income; and (3) among individuals who have a higher position in the company. The importance of these findings for the evolution of the polymorphism of handedness is discussed.