Do Genes Really Determine Your Hobbies, Relationships, and Voting Habits?

Over the past 25 years, we’ve become surprisingly comfortable with the idea that genes play a large role in our lives. When DNA is in the mix, people assume that it is the primary cause of whatever human trait is being talked about. People may choose whether to pursue a hobby or a relationship based on test results—even though it means that they must dismiss the other information they have at their disposal. Judges have even used genetic tests to make sentencing decisions.

Even science has carried this idea to extremes. Genes, for example, are said to account for the difference between people who are perpetual cheaters and those in a lifelong committed relationship. Genes are said to be the reason why some people vote conservative while others vote liberal and why some don’t vote at all. Genes supposedly determine our ability to get through those last years of college, to keep ourselves out of credit card debt, or to invest in the stock market in order to plan for our retirement. And on and on.

If...