Handedness and aggressive behavior in an Ntumu village in southern Cameroon

Abstract

Handedness in humans is possibly maintained by a frequency-dependent advantage during aggressive interactions. To contribute to relevant data related to this idea, functional handedness has been measured in a traditional ethnic group (Ntumu) from southern Cameroon, and confronted to the level of aggressive behavior. Functional handedness was measured by the hand holding the machete, an asymmetric tool used every day. Aggressive behavior was assessed by the frequency of occurrence of the traditional tribunal for solving internal conflicts. There was a low percentage of left-handers (8.1%), with no significant sex differences, although females below 50 year old displayed a significant increase of left-handedness with age. The level of aggressive behavior was low, as the traditional tribunal took place only seven times during the last five years. Results are discussed in the context of the evolution of handedness and the possible recent societal changes following European colonisation.