Language and schizophrenia make us uniquely human

ABC Radio National’s science programme Ockham’s Razor just had a fascinating edition on a maverick theory about schizophrenia and the evolution of language.

It purports to discuss the history of schizophrenia but is really a great summary of psychiatrist Tim Crow’s theory that schizophrenia is the consequence of the human evolution of language.

Crow is a professor of psychiatry at Oxford University who heads up a large research group so is quite mainstream to be a maverick, but his theory ruffles a lot of feathers.

He tries to address the puzzle over why schizophrenia has survived in the population if it is strongly influenced by genetics, particularly as it markedly reduces chances of reproduction. Surely it would have been ‘bred out’ of the population?

His theory [pdf] suggests that schizophrenia is the breakdown of the normal left-sided brain specialisation for language, owing to the disruption of genes that are involved in making the left hemisphere dominant.

Like other theories that attempt to account for the puzzle, it suggests that the risk is increased by pathological combination of usually important genes.

Crow has amassed a great deal of evidence that people with schizophrenia show less left-sided dominance for language and have altered patterns of brain asymmetry that can be seen in brain structure as well as in functional tasks.

He is also highly critical of a lot of the current molecular genetic work in schizophrenia, and argues that epigenetic variation is key and that its possible to see where the genes altered in human evolution to make us more likely to have language and consequently develop schizophrenia.

If you want a great brief guide to his theory, this edition of Ockham’s Razor is a great discussion of the main points.

Link to Ockham’s Razor on Crow’s evolutionary approach.
pdf of scientific paper by Crow outlining his theory.

One thought on “Language and schizophrenia make us uniquely human”

  1. The original reason that these genes and imprinting become defective is the male biological clock and the way errors accumulate in the sperm making cells with age and with toxic exposure. Interesting idea to connect this phenomenon with the development of language.

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