“One of the most remarkable discoveries is that even most measures of the environment that are used in psychology—such as the quality of parenting, social support and life events—show significant genetic impact. How is this possible when environments have no DNA themselves? Genetic influence slips in because the environment is not randomly “out there” independent of us and our behavior. We select, modify and even create our environments in line with our genetic propensities. Correlations between such so-called environments and psychological traits don’t necessarily mean that the environments cause the traits. For example, parental negativity correlates with their children’s antisocial behavior, but this doesn’t mean that the parents cause their children’s antisocial behavior. Instead, this correlation is substantially caused by parents responding negatively to their children’s genetically-driven propensities.
“A second crucial discovery is that the environment works completely differently from the way environmentalists thought it worked. For most of the 20th century, environmental factors were called nurture because the family was thought to be crucial in determining environmentally who we become. Genetic research has shown that this is not the case. We would essentially be the same person if we had been adopted at birth and raised in a different family. Environmental influences are important, accounting for about half of the differences between us, but they are largely unsystematic, unstable and idiosyncratic—in a word, random.
“The DNA differences inherited from our parents at the moment of conception are the consistent, lifelong source of psychological individuality, the blueprint that makes us who we are. A blueprint is a plan. It is obviously not the same as the finished three-dimensional structure. The environment can alter this plan temporarily, but after these environmental bumps we bounce back to our genetic trajectory. DNA isn’t all that matters, but it matters more than everything else put together in terms of the stable psychological traits that make us who we are.
“These findings call for a radical rethink about parenting, education and the events that shape our lives. It also provides a novel perspective on equal opportunity, social mobility and the structure of society.
“The nature-nurture war is over. Nature wins, hands down.”