NEW YORK - With so many family gatherings this time of year, many of us notice that our siblings are turning into our parents, and some of our partners’ and friends’ kids are turning into their parents. That’s no illusion. As scientists have learned from “nature versus nurture” studies on twins and adoptees, humans become more like our biological parents and other family members as we get older.
This is a little scary. It’s not that we don’t love the anxious relative who can’t enjoy a holiday dinner because her stuffing wasn’t perfect, or the impulsive one who can’t stop at three glasses of eggnog even though he will regret it. It’s just unnerving to realize they are reflections of the selves we might become.
I learned about escalating family resemblances from talking with Robert Plomin, a behavioral geneticist at the King’s College London. He describes the phenomenon in his recent book, “Blueprint: How DNA Makes Us Who We Are.” At first, I thought the interview might be contentious, considering that I’d recently written a column titled “You Are Not Your DNA.”
It turned out we disagreed very little. He and I shared a fascination with families. His pioneering studies used families — following adopted kids as well as their birth mothers. He found that kids take after their birth mothers, but not their adoptive parents, in cognitive skills, interests and personality traits. And as they get older, the resemblance only gets stronger.
He attributes this to the fact that people with literary, musical, mathematical or scientific inclinations will construct environments that amplify these predispositions; they are not necessarily or primarily products of those environments. He even found adoptees resembled their birth mothers in such seemingly nongenetic traits as television watching and likelihood of getting divorced. But then, these are influenced by personality traits. (Not that the traits associated with divorce are necessarily bad. As my dad used to say, better a vacancy than a bad tenant — and as I’ve gotten older, I’ve come to agree more.)
The adoptive parents had surprisingly little influence on anything measurable. “Parents don’t have the levers to pull they think they do,” he said. Despite all the hype about tiger moms, teaching grit and 10,000 hours of practice, he said, the reality is that kids are not blobs of clay you can mold.
This does not mean that we’re shaped only by nature. It’s just that people have misunderstood nurture. To Plomin, nurture is not how you were parented but the multitude of slings and arrows you encounter in your life. As he put it in is book, “What makes us different environmentally are random experiences, not systematic forces like families.” We are molded by unpredictable forces, but the very nature of the clay is a mix of our ancestors.
Some reviewers have accused Plomin of being a genetic determinist — that is, putting too much emphasis on genes as the drivers of our futures. In the introduction to the book, he does indeed say that genetic testing could provide a sort of crystal ball.
But in our conversation, he said genetic tests (and family members) show us a future that might be — not a future that must be. You might have a high risk of becoming an alcoholic, and knowing that might make you more conscious about avoiding this outcome. He said he had a high risk of becoming overweight, and that he is indeed somewhat overweight and has fought the battle of the bulge for years. But he doesn’t think that means he can’t achieve a healthy weight.
Plomin has also studied twins and the similarities between monozygotic, or “identical,” twins. They share almost identical DNA and usually look quite similar, but of course they are unique individuals. That was strikingly illustrated in the recently released documentary “Three Identical Strangers,” about monozygotic triplets separated in infancy and reunited at 19. The three young men looked alike, had the same smile and the same gestures, but (spoiler alert) one was much more troubled than the other two and eventually committed suicide.
The filmmakers try to suggest that the adoptive father is to blame, though there was no convincing evidence that he did anything wrong. Reading Plomin’s book made me appreciate how brutally unfair this accusation may have been, and how dismissive of the influence of random slings and arrows.
Plomin is a great enthusiast for the newest generation of genetic tests, now capable of giving us information on traits that are influenced by a multitude of genes, including cognitive skills and personality traits. That might be considered an advance, as long as this information isn’t used against us — but there’s no guarantee it wouldn’t be used badly and stupidly by employers, teachers or people trying to sell us stuff we don’t need.
Even if I could get such results confidentially, there’s a limit to how much insight can be gleaned from various one-dimensional scales of personality traits — extroversion, for example, or neuroticism. There’s so much more richness in watching the way our parents and other relatives undermine their own happiness, or find it against the odds. They are not me, but they do share a good portion of DNA. We navigate around many of the same rocky shoals, but I imagine that if I’m careful, I can avoid running into them. Some of them.
But this might just be a personal preference for stories. I turn to science when I want to understand the natural world and trends in human behavior. For wisdom on how to live, I find myself increasingly gravitating toward novels, stories and people. My mom was the same way.
Science writer Faye Flam is a Bloomberg Opinion columnist.