The older you grow, the less your family background predicts your IQ and the better your genes predict it. An orphan of brilliant parents adopted into a family of dullards might do poorly at school but by middle age could end up a brilliant professor of quantum mechanics. An orphan of dullard parents, reared in a family of Nobel Prize-winners, might do well at school but by middle age may be working in a job that requires little reading or little deep thought. Numerically, the contribution of “shared environment” to variation in IQ in a western society is roughly 40 percent in people younger than 20. It then falls rapidly … Continue reading Matt Ridley