Bernard Crespi

Study on natural selection

November 1, 2007

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Schizophrenia may be a by-product of natural selection in human evolution, says a study co-authored by SFU evolutionary biologist Bernard Crespi. The findings, which appear in the Sept. ’07 Proceedings of the Royal Society B, show genes believed linked to schizophrenia are more likely to show evidence of natural selection than those not associated with the disorder.

"Schizophrenia poses an evolutionary-genetic paradox," says Crespi, with colleagues Steve Dorus (University of Bath) and Kyle Summers (East Carolina University). "It has a major impact on health and reproduction yet persists at about one per cent across human cultures."

Scientists have long thought that ‘positive selection’ may play a role in the persistence of schizophrenia despite its negative effects on reproductive fitness and high heritability.

These findings are the first genetic evidence consistent with the theory that schizophrenia represents, in part, a maladaptive by-product of adaptive changes in evolution, possibly linked to creativity and cognition.

"The selective forces underlying adaptive evolution of these genes are largely unknown," says Crespi. But given the complex genetics of schizophrenia, selection may act on a diverse array of morphological, physiological and psychological mechanisms during neural development.

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