The Price of Denying Human Nature

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There is a force working on you right now, as you read this sentence. It did when you chose what to eat this morning, when you gravitated toward certain friends and away from others, when you found some subjects effortless and others felt like pushing water uphill. From the womb to your final decade, it is the most consistent thing about you, more so than your opinions, your relationships, or your politics. It is your genome, and it has been pulling you, with the patience of geology, toward the person you were largely going to become.

It turns out that with time you discover and become who you are. This is one of the most replicated findings in the behavioral sciences. That we now know this is remarkable enough. But for how long, and at what cost we denied it, is on another level entirely.

Age increases heritability

Take two identical twins: Clones, in the genetic sense, they share 100% of their DNA. Separate them at birth. Raise them in different families, cities, or countries, if you like. Then measure them at intervals across their lives: weight, intelligence, personality, political views, likelihood of divorce and psychiatric outcomes.

Separated from their shared womb and raised in different worlds, these twins should diverge. The environment piles up; experience accumulates. By middle age, surely, two people raised so differently should be quite different people.

This experiment has been run many times. The opposite is true.

The correlation between identical twins raised apart increases with time. The older they get, the more similar they become. In personality, cognitive ability, and the choices they make about how to live. Separated at birth, raised on opposite sides of the world, they end up reading the same kinds of books, making the same kinds of jokes, sitting the same way in a chair.

By observing this naturally occurring experiment across thousands of individuals, researchers have produced heritability estimates, the portion of differences between people explained by inherited DNA differences. They are worth sitting with:

• Body weight: ~60%.
• Height: 80–90%.
• Eye color: ~95%.
• Intelligence: 50–80%, moving toward the higher end as people move through adulthood.

Wealth increases heritability

It rises as the environment improves. In populations experiencing deprivation, the environment explains a big share of the differences between people. This is because the variance in what people are exposed to shrinks. The differences left after environmental differences have been removed are genetic, by definition.

Equality of opportunity is the precondition for seeing our genetic differences. Giving everyone the same opportunities does not erase differences. It reveals them.

The progressive and the hereditarian are usually imagined as enemies. The data forces a strange alliance.

The non-shared environment black hole

Influences on our lives can be separated into genes and environment. The environment itself splits into two categories:

• Shared environment: What siblings grow up with together (same parents, home, socioeconomic background).
• Non-shared environment: Everything that makes siblings different (unique friends, experiences, luck, differential treatment).

One might expect the shared environment to matter a lot. Yet once basic needs are met, it contributes close to zero to the differences between individuals. Siblings raised under the same roof are no more alike than siblings raised apart.

Non-shared environment is another story: 50% of the variation in life outcomes remains unexplained by either genes or shared environment. This has been called the “black hole” of behavioral genetics.

Despite decades of effort, behavioral geneticists have found few reliable, replicable non-shared environmental influences. Much of what makes siblings different appears to be a mix of unpredictable developmental variation and factors we cannot yet statistically explain or control.

The Nature of Nurture

Robert Plomin showed that the amount of television children watch, the long-considered gold standard environmental variable, is 50% heritable. The chaos or order of a household, the social support a person reports receiving, and even where one lives are genetically influenced. This seems strange until you think about why.

What are these ‘environmental’ measures? What a person does with their world. Divorce is not something that passively happens to you. It is the outcome of a relationship, which reflects your social behavior, which is substantially heritable. The ‘environment’ that social scientists thought they were measuring was always, in significant part, the consequence of the nature they were studiously ignoring.

The correlation is real. The causal arrow runs in the opposite direction from what was assumed for decades, and through a mechanism (genetics) that no one in the parenting literature was looking for.

The same genetic inclination toward language and abstraction that makes the parent a reader makes the child receptive to books. The child who loves mathematics seeks mathematical friends, the mathematically gifted environment she inhabits at forty is something she built from the genetically influenced inclination she had at six. With time you become the author of your environment. And as an author, you have a style.

Unfalsifiable Parenting Stress

Much of what makes modern parenthood feel like a burden is the anxiety created by the blank-slate, the belief that you are the architect of your child’s outcomes, that every choice has developmental consequences, that the wrong school or the wrong amount of screen time is compounding into damage you will not see for 20 years. That is an enormous weight to ask someone to carry before they have decided whether to become a parent.

The weight is largely illusory. What children share with their parents in terms of outcomes is primarily nature, not nurture. The adoptive parents who provide a child with every conceivable enrichment see, by adolescence, essentially zero correlation between their parenting choices and the child’s intelligence, personality, and outcomes. The biological parents they have never met predict those outcomes substantially.

If only this were an isolated mistake in parenting discourse…

In the early 1970s, the leading textbooks in psychiatry taught that schizophrenia was caused by what your mother did to you in the first three years of life.

Think about what that means. A mother whose child develops schizophrenia was told that she had done this. That the psychosis tearing through her child’s mind was the delayed detonation of her own failures in the nursery.

There was no evidence for this. There has never been. It was the confident extrapolation of an ideology – the belief that the mind is written entirely by experience; pathology is therefore always the inscription of a bad environment. The ideology came first, the theory was confected around it.

We now know that schizophrenia is among the most heritable of psychiatric conditions, 80%. Neither the mother nor the family caused it. The idea that they did caused decades of parents having guilt for a biological outcome they had no more caused than their child’s eye color.

This is what happens when a false theory of human nature becomes institutionally embedded. Sigmund Freud built the most influential psychological system of the twentieth century on the premise that what your parents did to you in the first five years of life was the primary determinant of your adult character and pathology. The theory was unfalsifiable by design, like a religion, any evidence against it could be reinterpreted as resistance or repression. It spread not because it explained the data but because it confirmed a prior: that who you are is sculpted, that the making of a person is primarily done by the environment, specifically by the family.

This led to conversion therapy for homosexuality, mother-blaming for autism (the ‘refrigerator mother’ hypothesis by Bruno Bettelheim, believed for decades), and the emergence of an entire therapeutic industry on interventions whose efficacy proved zero for the conditions Freud claimed to treat.

If these lessons spread, it would remove one of the main reasons people who might otherwise want children talk themselves out of it. Parents matter. But if they are reasonably good, they do not make a difference. They are not, in any way, the manufacturers, carpenters or gardeners of personality, intelligence, or psychological outcomes. What you provide is not a manufacturing environment. It is a relationship. And relationships, unlike manufacturing processes, are something human beings have always found worth having.

The love between parent and child is not a cultural preference that can be engineered away and replaced. It is one of the deepest drives evolution has built into us. The person who has not had children and wonders in their sixties what they missed is not failing to optimize a lifestyle. They are feeling the pull of something older than mammals.

From wasting billions to killing tens of millions

The expansion of the university system in the late twentieth century was caused, in big part, by an implicit belief in the blank slate: that higher education increases cognitive ability, productivity, and life outcomes.

Much of the observed correlation between university attendance and later success, to the dismay of the whole industry, is explained by a selection effect: students admitted to universities are already higher in cognitive ability and socioeconomic status before any instruction occurs. Much of higher education is a circus paid for by the taxpayer, a huge mismatch between what the market demands and the educational system supplies. This is to be expected from centrally planned economies. Central planners, turns out, tend to like the blank slate a lot.

Karl Marx built a political system on a similar premise. The New Soviet Man was the blank slate as state policy: human nature is malleable, false consciousness can be corrected by the right institutional arrangement. The right environment will produce the ideal person. The body count of this error, across the Soviet Union, Maoist China, Cambodia, and North Korea, is upwards of 100 million, and growing.

The blank-slate licenses coercion. If human nature exists, there are limits to what you can do to a person, a point beyond which their nature will resist, reassert, refuse. Something will be given higher loyalty than the state. The blank-slateist recognizes no floor at all. You can always do more. You can always go further. You can always try communism in another country because it hasn’t been done right yet.

The standard response at this point to save the face of the Soviets is to say that there were other centrally planning bad guys who weren’t them, invoking the Nazis. The mere mention of genetics, we are told, leads to atrocity, and the Holocaust stands as the permanent warning against any science that touches human nature. The Nazis are the cautionary tale of what happens when you inspect human nature, and the blank-slate regimes are a separate, unrelated tragedy at worst and the antidote at best.

The Nazis did use the language of genetics. But it was a fig leaf, not a cause. They were going to do what they did regardless, the eliminationism preceded the biology and bore no accurate relationship to it. The people they killed were not, as any honest analysis would have predicted, the least fit. They were often the most cognitively gifted populations on the continent. It was murder dressed in a lab coat. Interestingly, now the only politically correct explanation when discussing differences in outcomes between the sexes or other groups is the blank slate, another murder dressed in a lab coat.

The Nazis and the Soviets shared a common error: having ideology define their perception of individuals rather than letting individuals constrain ideology. The difference is in the direction of the projection. Nazi ideology treated people as bearers of fixed, essential properties. Soviet ideology treated people as raw material whose nature could be overwritten by the environment. In both cases, the result was mass dehumanization and suffering. The gulag and the concentration camps are not an aberration of extreme environmentalist ideology. They are its conclusion.

The insights our best science has produced look nothing like either. They don’t tell you that someone is part of the inferior or superior race or what should be done to someone to get a desired outcome. They tell you what is probable, what is tractable, and what is not. In doing so, it returns agency to the individual that the ideologue had. To know your genetic risk for obesity is not to be condemned by it. It is to stop fighting the wrong battle and start fighting the one you can win. How could knowing about something that was always there leave you less free?

Knowing our nature makes us more free. Knowledge is power. If anything is serfdom, it’s ignorance. Serfdom to a nature that doesn’t stop existing for being ignored. Understanding ourselves tells us where the degrees of freedom actually are. The person most determined by their nature is the one who knows nothing about it. 

The enlightened alternative

This is neither fatalism nor determinism. The Stoics understood this before genetics provided the mechanism. Reinhold Niebuhr’s Serenity Prayer – ‘grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference’ – is a prescription to direct effort at the levers that move.

The person who knows their polygenic scores is in a position to get a slim figure while being in the 95th-percentile for body weight. Knowledge of one’s genome reduces the tightness of the link between genes and outcomes. The studies were made with people who were not accounting for their genetic predispositions. Once you become mindful of them, you can do something about it. Remove the junk food from the house. Never rely on in-the-moment willpower when a crafted mindful environment can do the work.

On top of being most determined by their genes, the person who ignores having a nature is condemned to something worse than determinism: an obscurantist mystery. Unable to explain why they keep gaining weight despite trying. Unable to understand why their child, given every advantage, struggles in ways their other child does not. They keep stumbling on the same rock because they don’t see the rock.

“Man will become better only when you make him see what he is like.” – Anton Chekhov

This is the proposition the Enlightenment was built on. That clear sight precedes improvement, that an accurate map is a precondition of good navigation. The genetics revolution of the last 50 years has led to the most accurate map of human nature ever drawn. The twin and the adoption studies, the genome-wide associations and the polygenic scores; they all converge on a picture that is – once you let go of the ideology that made it seem threatening – deeply humane.