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.
Coren et al. (1986) extended these results to demonstrate that sinistrality is associated with maturational delays in nonclinical samples. They tested 713 females and 467 males and assessed their relative rate of physical maturation using the onset of secondary sexual characteristics, age of menarche, and relative body size as their indicators. They were able to demonstrate that delayed rates of maturation were associated with an increased incidence of left-handedness for both the males and females in their samples. Also consistent with the notion that left-handers have delayed maturation is Coren's (1989b) observation that left-handedness is associated with somewhat smaller body size in terms of both height and weight." (Coren, S. & Halpern, D.F. (1991) Left-handedness: A marker for decreased survival fitness. Psychological Bulletin 109: 99)