June 29, 2006

Reproductive success of left-handers

Evolution and Human Behavior (Article in Press)

Handedness and reproductive success in two large cohorts of French adults

Charlotte Faurie et al.


Left- and right-handers in humans coexist at least since the Paleolithic, and this variation in hand preference has a heritable basis. Because there is extensive evidence of an association between left-handedness and several fitness costs, the persistence of the polymorphism requires an explanation. It is not known whether the frequency of left-handedness in Western societies is stable or not. If the polymorphism is at equilibrium and maintained by frequency dependence, it implies that the fitness of left-handers equals that of right-handers. On the contrary, if left- and right-handers have a different fitness, the polymorphism will evolve. Using two large cohorts of French adults (men and women), we investigated the relations between handedness and several estimators of the reproductive value: marital status, number of sexual partners (of the opposite sex), number of children, and number of grandchildren. Left-handers seem to have disadvantages for some life-history traits, such as marital status (for women) and number of children. For other traits, we observed sex-dependent interactions with socioeconomic status: for high-income categories, left-handed women report less sex partners and left-handed men have more grandchildren. These kinds of interactions are to be expected under the hypothesis that the polymorphism of handedness is stable.


1 comment:

shenandoah said...


I notice the curious detail, that all five of the Indian warriors posing with their guns in this antique photograph seem to be left-handed (unless the negative got reversed, anyway).

As a left-hander myself (who sometimes practices marksmanship), I know that even the men holding the rifles on their left side, are also left-handed (apparently).

I wonder what percentage of Native Americans were left-handed, prior to the Columbus and later invasions.

Although part Cherokee (matrilineally) on Mother's side of the family, I seem to have inherited my left-handedness from my father (R1b1a2 European ancestry).

I wonder if left-handedness was more common among paleolithic types (Cro-Magnon, specifically).