Consumer DNA testing promises to reveal distant relatives, health risks and even personality traits. But the science is often misunderstood, with companies hyping what genes can truly tell us. As geneticist Michael “Doc” Edge and economist Patrick Turley point out, DNA is no oracle. It can’t fully convey who we are or predict our future.

Here are five common myths:

1. Genetics define race

Race and ethnicity are principally social categories, not biological. Although some genetic variation is associated with the places where one’s recent ancestors came from, U.S. Census categories are not a good description of that variation. “Average genetic differences between people who identify as members of different races are not nearly as large as many people imagine,” says Edge.

2. There is a gene for intelligence

Traits such as intelligence are shaped by many genes — along with environment, opportunity and life experience. There is no single “intelligence gene,” and no gene for personality traits, either.

3. DNA determines your future

Genes can influence behavior and health in certain directions, but they don’t dictate outcomes. “DNA isn’t destiny,” says Turley.

4. Knowing your genes will make you healthier

In some cases, genetic testing may backfire. Discovering a lower risk for, say, heart disease could lead someone to adopt a less healthy lifestyle. “A downside to genetic testing is that it could lead people to increase their risk,” says Turley.

5. DNA is a biological family tree

In fact, our genome offers but a small glimpse into our ancestral past. We inherit only half of each parent’s genetic material — and just a fraction of our ancestors’ over time. After 10 generations, we may share no measurable DNA with most of our forebears.

—T.W.