For the general public, the question of whether genes contribute to a person’s intelligence is a matter of controversy. Among intelligence researchers, there is no doubt that variation in intelligence is partly attributable to genes. In fact, the purpose of the very first twin study, done back in 1924, was to study the contribution of genes to intelligence. Today, researchers can predict how similar the IQ scores of people will be based on how similar their genes are. Such work has confirmed what twin studies have long shown: In adulthood, the majority of variation in intelligence is caused by genes. We now know about many genes that can be used to predict intelligence. Geneticists can determine which version of these genes someone has and, based on how many IQ-enhancing and IQ-deflating gene…