Sexual selection, timing and the descent of man: A theory of the genetic origins of language

A theory of the evolution of language is presented that invokes a critical role for a single gene that biasses one hemisphere to be "dominant" with re spect to the other. Evidence that this gene is located in the class that is present in homologous form on the X and Y chromosomes reveals a role for s exual selection in generating and maintaining a sexual dimorphism with resp ect to cerebral asymmetry. Such a gene could account for sex differences in verbal and spatial ability. In the context of Bolk's (1926) theory that Ho mo sapiens evolved by a process of neoteny [delayed maturation], it can be seen that a difference in timing of procreation in the two sexes acting upo n the variation associated with a single gene to influence the plateau of b rain growth could be relevant to changes in brain size and the capacity for communication with con-specifics. The genetic change that introduced the b ias in hemispheric development is a candidate for the "speciation event" fo r modern Homo sapiens. The proposed mechanism [bi-hemispheric differentiati on of function - with phonological [phonemic] sequencing confined to the do minant and spatial [logical] organisation taking place largely in the non-d ominant hemisphere] provides a substrate for the most distinctive feature o f language - its generativity. Whatever the mechanism, the speciation event appears to have carried with it genetic variation that reflects a balanced polymorphism or the operation of a high mutation site. It is argued that a component of this variation is the parallel evolutionary enigma of psychos is, and that the nuclear symptoms of schizophrenia can be understood as the "price that Homo sapiens pays for language".