Schizophrenia's Evolutionary Enigma: The Cliff Edge Fitness Model
The genetic basis and high prevalence of schizophrenia have long been a puzzle in evolutionary biology. Traditional theories struggle to explain its persistence. This post introduces the "cliff edge fitness model," which proposes that certain cognitive and social traits enhance fitness up to a threshold, beyond which they lead to severe disorders like schizophrenia. This model explains the observation of both positive and negative selection on schizophrenia-related genes and predicts a complex relationship between polygenic risk scores and reproductive success. Research suggests that while schizophrenia itself is detrimental, its associated genes may have conferred other benefits during evolution, such as enhanced cognitive abilities. The model highlights that evolution optimizes for gene transmission, not individual health, explaining why some diseases persist with high heritability and prevalence.
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