I hope you're sitting down. As I mentioned in my recent newsletter, Behavioral Geneticist Robert Plomin has some . . . news regarding the field that he has been in for over 40 years. He has seen all of the advances in the science of DNA over those years, and evidently the past few years have shown us (and confirmed) a few choice tidbits that he has become known for:
Parents matter, but they don't make a difference.
Education matters, but it doesn't make a difference.
Life events matter, but guess what? They don't make a difference, either.
As you might imagine, this message has gone over like a lead balloon. But it's important to note that this isn't his opinion. These studies aren't involved in the replication crisis psychology is dealing with. The studies have continuously confirmed each other since genome sequencing began.
What the heck does Plomin mean with his claims-that-make-you-go-hmmmm? Let's deconstruct.
Plomin understands that people--particularly parent-people--get upset when they hear his claims. He tries to console us but I wasn't feeling it. He's such a lovely guy who breathes his field, as you can hear in episode #211 of The Making Sense podcast with Sam Harris. He's a pleasure to listen to--so much so that I listened to the audio version of this book because I wanted to hear more of his voice.
What he means by his controversial-yet-catchy conclusions is that, as he is fond of saying, "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."
The fact is that we are the same as every other human being for 99% of the three billion steps that are genetic--the blueprints for human nature. Less than 1% of the DNA steps that differ between us make us who we are as unique individuals.
The Research: Twins and Adoption
You may know that twin studies have taught us much of what we know about the importance of genetics. Monozygotic (identical) twins share 100% of their DNA, while dizygotic (fraternal) twins share 50%, just like any other sibling pair. What makes siblings different, therefore, is their DNA differences. That's why they can grow up in a shared environment and turn out completely different. But they will all become more and more who they are as they age. We all do. And we end up more like our parents than not on many measures studied (BMI, height, educational attainment).
Adoptees, however, end up more like their genetic parents. This is a crucial finding. Despite, for instance, someone adopting a child and providing them with healthy food, exercise, and habits, if the child's genetic propensity is to be overweight, that is likely what will occur. The weight of adoptees doesn't correlate with that of adoptive parents, but it does correlate with genetic parents. Genes are not destiny, Plomin says, but they might mean that it's more difficult for you to overcome certain obstacles.
The Nature of Nurture
Plomin talks/writes a lot about the nature of nurture, which means that much of what we think is due to environment is really due to heredity, and we are able to tease much of that apart. What we receive in our lives is what we actually experience, he says, but what we perceive is heritable.
For instance, life events can be considered what we receive. But how we respond to them is heritable. That's why they don't end up making much of a difference in who we are. They might contribute to the meaning of our lives, but they don't change who we are. Things happen, but we bounce back to our genetic programming.
Furthermore, environmental differences are important, but mostly random, unsystematic, and unstable, and so we can't do very much about them. We can do something about how we prepare for and meet them, however how we actually do this is largely determined by our DNA. Not completely--largely. Plomin is fond of saying: "Heritability describes what is, not what could be." This is what he means by the nature of nurture. There's a lot of DNA baked into us that informs what we do with the environment, which means the environment isn't as powerful as we tend to think it is. "Individual differences in response to stressful life events are genetic."
On One-Gene Dreams
We used to be in search of The Gene that would be the cause of such-and-such trait or disorder. This is particularly true in psychology, where to date I think we have discovered exactly zero single-gene disorders. There is no gene for schizophrenia. Or bipolar disorder, or autism spectrum disorder. There are very few single-gene disorders or traits, and the ones we have found are rare.
Instead, our individual differences in millions of DNA sequences are what account for whether or not we end up with Alzheimer's disease, high blood pressure, or obesity. Most disorders are polygenic. That's a lot less dramatic and a lot more vague. It reminds me of early neuroscience thinking that there were discrete areas of the brain that more-or-less controlled--were the centers of--certain behaviors or abilities. But as it turns out, the brain is a massively complex organ that is capable of many functions in many places, and/or single functions are really the purview of vast networks across several regions.
Here's how I think about it: I like the way Sonja Lyubomirsky talks about happiness. Fifty percent of your happiness comes from your genetics (confirmed by Plomin). Ten percent comes from life events (and we're talking about becoming a paraplegic, marrying a certain person, getting fired, or winning the lottery). Life events, according to the research, don't move the needle much when it comes to who you are and whether you are happy.
But, as Lyubomirsky and others have shown, the intentional behaviors and habits you craft into your life can make a difference (40%-max-but that's better than nothing). Habits like doing things for other people, savoring pleasant moments and emotions, gratitude, self-compassion, and present moment awareness are the difference-makers.
So instead of concerning yourself with buying a luxury-brand car, go walk some dogs at your local shelter or start a garden or call a friend on the phone and actually talk to that person about their life and thoughts and feelings. Go to the beach or the lake or the mountain, have a seat, and just listen to the sounds around you and feel what is going on inside your body and on its surface. Being happy in your life is different from being happy with your life (Laurie Santos).
Mindfulness is a wonderful way to learn about all of these things--their importance, the research, and how to cultivate the habits. Go here if you're interested and sign up for an Intro or a course!