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An evolutionary theory of schizophrenia: cortical connectivity, metarepresentation and the social brain

Burns, Jonathan Kenneth An evolutionary theory of schizophrenia: cortical connectivity, metarepresentation and the social brain.

Short Abstract:

Schizophrenia is a universal disorder with largely genetic aetiology. A theory is proposed that schizophrenia is a disorder of cortical and specifically fronto-temporal connectivity that evolved in association with emerging complex neural circuitry in human ancestors. These circuits evolved under selective pressures involving group living, and regulate aspects of social cognition such as metarepresentation and affective responsiveness. Evidence from various scientific fields suggests that the evolutionary advantages conferred by these changes rendered the hominid brain vulnerable to insults. I argue that schizophrenia exists as a costly trade-off in the evolution of social cognition and the creative mind.

Long Abstract:

Schizophrenia is a worldwide prevalent disorder with multifactorial but highly genetic aetiology. Prevalence rates are approximately 1% in most societies surveyed, despite lowered fertility in affected individuals. Thus it is argued that an evolutionary advantage exists in genetically related unaffected relatives. Various theories of ultimate causation of the schizophrenic genotype and Tim Crow’s hypothesis regarding cerebral asymmetry and language are reviewed and found wanting. In keeping with available biological and psychological evidence, an alternative theory of the origins of this disorder is proposed. Schizophrenia exists as a costly trade off at two stages in the evolution of metacognition and the social brain. Paleoanthropological and comparative primate research suggests that hominids evolved complex cortical interconnectivity (in particular fronto-temporal circuits) in order to regulate social cognition and the intellectual demands of group living. Ontogenetic mechanisms underlying this cerebral adaptation rendered the hominid brain vulnerable to genetic and environmental insults. This is the first trade off experienced by hominid ancestors. I argue that genetic events occurring prior to the migration of H. sapiens out of Africa 150 -100 000 years ago gave rise to a genetic spectrum that, in it’s homozygous form resulted in the schizophrenic phenotype, while heterozygous ‘schizotypal’ individuals possessed cognitive advantages that enhanced their relative fitness. Thus schizophrenia evolved as a trade off firstly in the emergence of complex social cognition and secondly in the emergence of a phenotype that exhibited unusual creativity and iconoclasm and may be associated with the great cultural and scientific advances of human history.

Keywords:	adaptation, cognition, connectivity, creativity, evolution, evolutionary psychiatry, metarepresentation, primates, schizophrenia.
Comments:	In your instructions for authors you specify that the short abstract should be up to 100 words and the long abstract up to 250 words. I have thus written abstracts of 97 and 248 words respectively. I note that the above instructions specify 60 and 150 words respectively and hope this is not a problem. If the abstracts are too long I would be very happy to rewrite them.
Subjects:	Biology: Evolution Psychology: Comparative Psychology Neuroscience: Neuropsychiatry
ID code:	bbs00001188
Deposited by:	Jonathan Burns on 12 April 2002