Bilateral asymmetry in left handers increased concerning morphological laterality in a recent sample of young adults.

Abstract

Handedness is a major trait of humans, generating a measurable directional bilateral asymmetry in the upper extremities. In most cultures, right handedness is genetically more frequent (90%) and socially supported, even if reskilling became unusual. The present anthropometric study was conducted in 2014 with 76 right and 26 left handers born after 1985 to detect, whether right as well as left handedness produces significant morphological differences in the bones of the person's upper extremity and its handgrip strength, as it has been proven repeatedly only for right handers. In this sample, right handers show a clear right directional asymmetry in 5 out of 8 measures, with the highest differences between their right and left extremity in hand breadth and forearm length. Left handers have a significant higher left elbow breadth compared to their right extremity, but did not show any other measurable differences. This indicates a more symmetric training of their arms and less influence of handedness, even if reskilling and specialised manual activities were excluded in this study. Further, there still have to be differences in the usage of the main hand in everyday life for right and left handers. Probably, left handers still have to use the right hand more often for unimanual tasks than right handers their left hand. Nevertheless, our results indicate a slight change to more morphological laterality in left handers in the past 30 years.