Handedness, or manual laterality of function, is thought to be both universal and unique to humans, making it a highly derived trait, based on an equally specialized neural substrate. By contrast, in various non-human species, both living and extinct, extent of lateralization varies. All known populations of living human beings apparently favor the right hand, motorically, culturally, and symbolically, thus right-handedness is species-typical, as well as species-specific. This laterality of function is correlated with asymmetry of structure, that is, neural, skeletal and muscular, for...