On the evolution of human syntactic ability. Its pre-adaptive Bases—Motor control and speech

Abstract

The evolution of the particular, species-specific, neural substrate that underlies human syntactic and phonologic ability may be the result of two stages of pre-adaptation involving automatization for complex goal-directed motor control. The neural mechanisms of the non-human primate brain that evolved to enhance the automatization of orofacial motor control appear to be the homologue of Broca's area in the human brain. These mechanisms may have been preadapted in certain hominids for the evolution of neural mechanisms adapted for automatized speech articulation, matched to the development of the human supralaryngeal vocal tract. Recent data show that the articulatory maneuver that underly the production of human speech appear to be the most complex that human beings master. The selective pressure for the automatization of articulatory activity for speech production on the neural mechanisms of Broca's area in the hominids ancestral to anatomically modern homo sepiens yielded a neural substrate suited to complex rule-governed behavior in the linguistic domains of phonology and syntax. The theory predicts correlations between the speech production and syntactic deficits of chimpanzees, as well as correlations between syntactic deficits and speech production deficits in aphasia, and some instances of deafness. The development of patterned motor activity and syntactic and phonologic ability in human children may also be connected.