A theory of the origin of cerebral asymmetry: epigenetic variation superimposed on a fixed right-shift

Laterality. 2010 May;15(3):289-303. doi: 10.1080/13576500902734900. Epub 2009 Mar 13.


A theory of the genetic basis of cerebral asymmetry is outlined according to which (1) a single right-shift factor in all human individuals interacts with (2) epigenetic variation that is apparently random, transmissible between parent and child, but with a half-life extending over a small number of generations. The right-shift factor arose late (150 to 200 thousand years ago [KYA]) in hominid evolution as a mutation in the X copy of a gene pair (Protocadherin 11XY) in a region of homology between the X and Y chromosomes created by a duplication 6MYA at the chimpanzee hominid separation. The epigenetic imprint originates in the process now known as "meiotic suppression of unpaired chromosomes" (MSUC); it reflects random pairing of partly homologous X and Y chromosome regions in male meiosis, and confers species-specific diversity of cerebral structure on the human population.

MeSH terms

  • Brain / physiology*
  • Chromosomes, Human, X / genetics
  • Chromosomes, Human, Y / genetics
  • Cognition / physiology
  • Epigenesis, Genetic / genetics*
  • Female
  • Functional Laterality / genetics*
  • Humans
  • Individuality
  • Language
  • Male
  • Models, Genetic*