Historical Variability in Heritable General Intelligence: Its Evolutionary Origins and Socio-Cultural Consequences

It has recently been demonstrated that reconstructed changes in Western genotypic IQ means which trend in the same direction as the Western historical status-fertility relation (i.e. positively up until 1850 and then negatively after) are strong predictors of changes in the rates of significant innovation in science and technology. A prediction from 'smart fraction' theory is that this effect should be strongly mediated by changes in the per capita numbers of eminent individuals, i.e. those who actually generate the significant innovation. This hypothesis is tested using a combination of growth curve and path analyses in which serially autoregressive and Flynn effects over time are also considered. Consistent with smart fraction theory, eminent individuals mediate the impact of changing genotypic IQ on innovation rates, whereas rising phenotypic IQ has had no effect on either the per capita numbers of eminent individuals, or innovation rates. These findings are evaluated in the context of a multilevel selection model, which connects individual-level selection for a declining within-population mean IQ with group-level selection for a rising between-population mean IQ. The dynamics of these two opposing processes during the last half-millennium are presented as supportive of this model.