Concerning the origin of handedness in humans.
The origin of right-handedness as the predominant chirality in humans seems to be related to the tendency of human (and presumably prehuman) mothers to hold infants on the left side. The latter practice has previously been ascribed to imprinting and the soothing sound of the mother's heartbeat on the infant. Given the practice of holding the child in this manner, dextral mothers will be more skillful at manipulation of objects and selectively favored.
D005075:Biological Evolution; D007839:Functional Laterality; D006801:Humans; D009034:Mother-Child Relations