In my last post, I suggested that intelligence, or more precisely neural plasticity, was originally an infant trait in ancestral humans. In modern humans, it seems to have progressively been extended into older age groups.
This isn’t a novel idea. It has been put forward by such people as Ashley Montagu (1989), Stephen J. Gould (1977), and Konrad Lorenz (1971). Interestingly, one author has argued that this persistent brain plasticity has made the human mind more susceptible to certain neuroses and other personality disorders.
Therefore, psychotic disorders may be the ‘price’ for the delay of maturation and for the rapid increase of brain size during the past 150,000 years. For example, normal development of the human nervous system is particularly dependent on sensory input. Social deprivation leads to stereotyped and self-injurious behaviour, resulting from an alteration of dopamine receptor sensitivity. The assumption of an enhanced susceptibility to psychotic disorders by delayed maturation may be underlined by the fact that most psychiatric disorders originate in early childhood, when the growth rate of the brain and acquisition of learned material is particularly high. (Brüne, 2000)
This point is interesting because it links up with Dr. Kawecki’s suggestion that “some diseases are a byproduct of intelligence” (see previous post).
Brüne, M. (2000). Neoteny, psychiatric disorders and the social brain: hypotheses on heterochrony and the modularity of the mind. Anthropology & Medicine, 7(3), 301-318.
Gould, S.J. (1977). Ontogeny and Phylogeny. Cambridge: Harvard University Press.
Lorenz, K. (1971). Studies in Animal and Human Behaviour, Vol 2. London: Methuen & Co.
Montagu, M.F.A. (1989). Growing Young. 2nd ed. New York: Bergin & Garvey.