The short timescale of massive secular IQ gains (“Flynn Effect”) is inconsistent with positive selection of a recent gene mutation, but other genetic mechanisms are possible. Principles of evolutionary psychology, combined with secular trends, suggest an epigenetic explanation: the Cognitive Genome Optimization Hypothesis. Per life-history theory, favorable secular trends may change the phenotypic expression of the genotype which controls the neurophysiology of problem solving. The hypothesis posits two intermediate steps between reliable nutrition (the starting point) and higher IQs (ending point): (1) Earlier cognitive maturation and (2) further calibration of cognitive function by reliable social resources (cultural complexity, mandatory education). Unlike earlier generations, more resources can be deployed to cognitive maturation than to physical survival, and more time is available to calibrate cognitive processing into the upper end of the trait value range for intelligence. The secular trend of earlier puberty timing is critical: data show an association between puberty and higher IQ.
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