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.
Geschwind and Levitsky (1967) reported that in 100 postmortems, a larger planum was found on the left side in 65 brains, on the right side in 11 and in the remaining 24 the two sides were about equal. Galaburda et al. (1987) looked at the actual sizes of the plana on each side in this same series. They found that in symmetrical brains, both plana were large, while in asymmetrical ones (the typical pattern) the size of the planum on the right side was reduced, while the left stayed about the same. Thus, the typical pattern of asymmetry seems to be associated with a reduction on the right side, rather than expansion on the left; and symmetrical brains show no reduction on either side. Similarly, for the right and left hands, it looks as though bias to the right hand depends on loss of left hand skill, rather than increased skill on the right. (Annett M (1991) Right hemisphere costs of right handedness in Vision and Visual Dyslexia, Stein JF (ed.) CRC Press, Boca Raton pp. 87)