A combination of twin studies and psychometric testing has repeatedly shown us that most measurable human behaviors have some kind of heritable component as well. Of particular interest has been intelligence, as measured by an IQ score or standardized tests. Over a century’s worth of data has converged on a few key points: Intelligence is highly heritable; it is expressed via a great many genetic variants; and it is predictive of certain life outcomes. Taken together, these suggest that our evolutionary history has generated a set of genetic variants that can have relevant influence over our environment—the extended phenotype come to life.