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.
"Because body size can evolve in these different ways, by change in different components of growth, the parallel change induced in brain size may differ. This will depend upon the timing, during growth, of pleiotropic gene effects. For example, if pleiotropic gene effects influencing these two traits occur mostly in the early portions of body growth, body-size evolution occurring by change in later growth will induce little parallel change in brain size. Evolution occurring by change in early growth, however, will induce greater change in brain size for a given amount of body-size evolution." (Riska, B. & Atchley, W.R. (1985) Genetics of growth predict patterns of brain-size evolution. Science 229: pp. 669)