Human evolution theory utilizing concepts of neoteny & female sexual selection
An etiology of neuropsychological disorders such as autism and dyslexia, and the origin of left handedness.
"That is, gestural language more directly captures the actual shapes of things and their dispositions in space. Given the preadaptation to voluntary control of the upper limbs and to the mapping of manual action onto the perception of action, it would have been natural for our early ancestors to develop gesture rather than vocalization for the purposes of intentional communication." (Corballis, M.C. (1999) The gestural origins of language web link)