Our Fortunetelling Genes

When I was a graduate student in the early 1970s, psychology was dominated by environmentalism, the view that we are what we learn. It was dangerous professionally (and sometimes personally) even to raise the possibility of genetic influence. We were taught, for example, that schizophrenia was caused by what your mother did to you in the first few years of life.

Since then, a mountain of evidence from twin and adoption studies has convinced most scientists that disorders like schizophrenia and traits like cognitive ability run in families for reasons of nature (genetics) not nurture (environment). What is new in the last few years is the DNA revolution. Our ability to read the genetic blueprint of individuals and to predict, from birth, their psychological dispositions is growing by the day. It promises to transform not just how we understand ourselves but how we deal with a range of personal and social problems.

About 99% of the 6 billion steps in the spiral staircase of DNA’s double helix are the same for all of us. This is what makes us human. Behavioral geneticists are interested in the 1% of DNA that makes us individuals. A century of research has found that these inherited DNA differences account for about 90% of the differences in people’s physical traits, such as height and eye color. What may come as a surprise is that DNA also accounts, on average, for about 50% of our differences in such psychological traits as personality, mental health and illness, and cognitive ability and disability.

Read the whole story (subscription may be required): The Wall Street Journal