The Misplaced Faith in Nurture

 The nature vs. nurture debate persists in the public imagination as if it were an eternal philosophical puzzle driven by my misconstrued feelings. However, the scientific reality is clear: genes are the dominant, systematic force shaping who we are. Of course, the environment (ex. nurture) plays a role, but its influence is instead minor, inconsistent, and often overstated when discussing personality, intelligence achievement, or life outcomes like career success and health. I hope to demonstrate this truth and allow you to see the ridiculousness in giving nature and nurture equal weight as if it were that simple.
    To start genes are segments of DNA coding for proteins or regulating their production, serving as biological instructions for building and maintaining the body. A common misconception is the idea of a single "gene for" complex traits like intelligence or depression. Genetic influence is far messier, operating through pleiotropy (one gene affecting multiple traits) and polygenicity (multiple genes affecting a single trait). Although there are rare exceptions, Huntington’s disease, for instance, caused by a single mutation, most behavioral traits emerge from complex genetic networks. Major depression, for instance, is heritable, yet no single gene (or even ten genes) directly "causes" it.
    Understanding heritability clarifies this complexity. Heritability measures the degree to which genetic differences explain variation in a trait within a population. And a trait is a physical or psychological (behavioral) characteristic that is stable over time.  If identical twins always share the same eye color (a trait), heritability is 100%. Depression has a heritability around 40%, meaning if one twin has depression, the other has roughly a 40% chance of going on to suffer as well. Crucially, heritability doesn’t imply inevitability, only that genes significantly influence differences among people. Genetics loads the gun, but often the environment pulls the trigger. Someone genetically predisposed to alcoholism, for instance, cannot develop alcoholism if there is no alcohol available.
    Yet, environment’s role is crucial, though nuanced and not what we traditionally think. In certain extreme cases, environmental deprivation alone can cause severe problems, regardless of genetic predisposition. Studies of Romanian orphans, who experienced severe neglect, malnutrition, and minimal social interaction, demonstrate permanent cognitive impairment and developmental delays, even absent family history of mental illness. Here, the environment doesn’t just pull the trigger, it loads and fires the gun.
Despite these exceptions, environment typically matters differently than most assume. It can be split into shared influences (parenting, schooling, socioeconomic status) and non-shared influences (unique experiences, random events, twists of fate). Decades of twin and adoption research consistently demonstrate minimal lasting impact from shared or unshared environmental factors. Identical twins raised apart show remarkable similarity in personality, intelligence, and quirks, while adoptive siblings end up no more alike than strangers. This sharply contrasts with the popular belief that parenting or upbringing decisively sculpts individuals. Parents instead encourage and support what is already there.
    Misunderstanding this has historically caused real harm. For decades, psychologists wrongly blamed "schizophrenogenic mothers" for schizophrenia and "refrigerator parents" for autism, theories that were not only incorrect but cruel, turning mental illness into moral failings often directed towards women. The story of the triplets from "Three Identical Strangers," separated at birth and raised in dramatically different environments, further underscores the dominance of genetic influence. Despite their radically different socioeconomic backgrounds, the triplets showed uncanny similarities in temperament, mannerisms, and preferences.
Moreover, all traits including depression or reading disabilities should be viewed as quantitative, not categorical. Psychiatry often acts as if someone either “has depression” or doesn’t, but this categorization is clinical convenience, not biological reality. Depression, like reading ability, exists along a continuum, from severely impaired to highly resilient and able. Genes don’t determine a categorical presence of depression but rather influence an individual's placement on this continuum.
    The obesity epidemic illustrates this interesting gene-environment interaction. Weight is highly heritable (around 70%), puzzling those who ask why obesity rates have surged when genes haven’t drastically changed. Some may point to toxin exposure and a deliberate corporate and government scheme to fatten us however the answer is pretty straightforward. We exist in a time where calories are more abundant and delicious than ever. And if we think about the traits that contribute to weight like food drive (how driven you are to seek out food, enjoy it and dismiss safety cues) and conscientiousness (specially low, preventing inhibition of delayed gratification or choosing less calorie dense options) they can only flourish in the kind of environment where calories are easily accessible and abundant (AKA the environment we live in). In the past if you had the propensity to have a high weight it simply couldn’t be that high as you existed in an environment with less: leisure time, food and calories dense, highly palatable and relatively cheap options.
    Socioeconomic status (SES), too, reveals large genetic influences often mistaken as purely environmental. SES is around 40% heritable, not because there's a "wealth gene," but because traits driving success (intelligence, conscientiousness, educational attainment) are themselves highly heritable. While systematic environmental factors play a role in understanding SES like race, and parental income the variance within groups is so large that ultimately they don't tell us much. The best predictor of a child's SES is instead inherited genetic predispositions.
None of this implies fatalism. Recognizing genetics' primary role doesn't negate compassion, social support, or policy interventions. It simply demands abandoning environmental determinism, a modern form of the failed science of behaviorism. We must deconstruct and move past  the belief that perfect parenting, schooling, or social programs guarantee equal outcomes. The truth is more complex but richer: genes set the foundational probabilities, environment allows growth and development, and chance introduces unpredictability. Accepting this nuanced reality allows more rational discussions and genuinely effective interventions geared at promoting equity and superior quality of life for all.

*For more please read "Blueprint" by Robert Plomin and consider "The Genetic Lottery" by Kathryn Paige Harden. This was my attempt at a summary