Schizophrenia about genetics

By Razib Khan | March 25, 2013 11:12 pm

The genetics of schizophrenia is a fertile if fraught topic. But I won’t be discussing that in this post. Rather, I want to put the spotlight on a peculiar contradictory and illogical tendency in the contemporary American Zeitgeist: the gene is all-powerful, and the gene is irrelevant. The same people who raise eyebrows with skepticism about the heritability of endophenotypes, nevertheless seem to believe that when it comes to the domain of disease genes are perfectly and frighteningly predictive! I know scientifically educated people who have expressed to me their confidence in the power of nurture, as opposed to nature, in the determination of the character of their potential offspring. And yet these same individuals may express serious worry that genetic testing might render the whole field of health insurance null and void. The problem with this perspective is that it is a robust behavior genetic finding that many traits have substantial heritable components. That is, the correlation between parent and offspring in a trait (e.g., personality) is not simply a function of environmental input. Similarly, for many diseases which have a biological basis the predictive value of a given set of genes, or even family history, is often imperfect. Biological development has a strong random component, which we can’t predict or control. This is true even for environmental inputs as well; there are people who have never smoked who die of lung cancer.

One component of this dichotomy is easy to characterize. Across various cultures the “nature vs. nurture” question has been answered differently. In the West a form of the “blank slate” arguably was prominent in the Enlightenment, only to disappear during the 19th and early 20th century, and to reappear with Behaviorism (at least in its more vulgar fashion). But that’s not the only issue at work here. Why do people believe that genes are so powerful in predicting disease, and the theoretical course of one’s life in a general sense? Why does the discovery of an Ashkenazi genetic background transform Neo-Nazis into Jews in an ideological sense? There are genetic variants which are correlated with Ashkenazi Jews, but there are no genes for Ashkenazi Jewish identity in a determinative sense. And, despite the superficial nurturist ideology which dominates American society (e.g., “no child left behind!”) the attraction to crass genetic determinism (e.g., “the God gene”) which explodes upon the popular culture periodically suggests that there is a latent undercurrent of genetic essentialism waiting to be tapped.

To get the root of what’s going on here we have to look to cognitive psychology, and how our minds are disposed toward organizing the world around us. We order the world, and see patterns. When Einstein asserted that “God does not throw dice,” he was not only reflecting a common theological position (mainstream among Sunni Muslims and Calvinists, and to some extent other religious traditions), but also a deep intuition that the world is as it is in a necessary sense. It is no accident. We are no accident. Time has a logic and order. Similarly, we see around us different classes of natural objects (e.g., inanimate vs. animate), and natural kinds of organisms (e.g., fish vs. fowl). The psychologist Paul Bloom, among others, has written about the tendency toward innate essentialism (see a Descartes’ Baby) at length. Even infants seem to perceive that the identity of an object or organism is not wrapped up simply in its exterior form or manifestation. The reflex that transgender individuals are essentially what they were born is a very primal sentiment.

Tied in with this essentialism is the idea that humans in particular have souls (the mind-body dichotomy), or specific seats of their being. Some of the ancients located the position of the soul, the identity, in the heart, while other did so in the head. Rene Descartes formalized the intuitions about the souls in a rigorous modern sense with his dualism (though obvious dualistic philosophies predate Descartes). One reason that modern cognitive neuroscience is so “sexy” is that even stone cold materialists likely have an intuition which corresponds to the general idea of the soul, and this scientific field plumbs those depths. “Human nature,” and its material embodiment, is a thing, rather than a collection of disparate phenomena welling up from banal material processes.

The peculiar tendency to imbue genes with great power also emerges from the intuition that individuals have essences, and those essences are not subject to the throw of the die. Pre-modern people did not have the idea of the gene, but the nature of the human mind is that it uses the contemporary furniture to make sense of the world, and render it comfortable and non-threatening. Ergo, the co-option of quantum mechanics by a variety of mystical beliefs. Similarly, the idea of a “genetic blueprint,” the “plan of development” for the human being, naturally merges with pre-existent intuitions as to a specific special instance of a human, and the nature of the fate of that instance. You are who you are, and you could be no other.

The problem is that nature corresponds only loosely with human intuition. This is more and more true as we move away from the scale of human life in a concrete and abstract sense. Human genealogical intuitions mislead us as we coalesce our ancestries back to a finite set of common founders. Inheritance seems blended, not discrete. Matter seems composed of fundamentally different essential constituents, rather than complex assortments of subatomic particles. In relation for what this means about genetics, it means that it matters in many contexts. But it is not an all or nothing affair. We wish to order the joints of the world by a discrete set of clean composed elements, but more often universe’s true form would seem to us more a confused mishmash. So be it. It is what it is.

MORE ABOUT: Genetics
  • Karch_Buttreau

    I think it’s simpler than that. It’s generations of educators clamoring for more taxpayer funding or for your checkbook that push this nuture versus nature agenda. Same reason that the church still pushes creation. It’s just business, and the more people that believe in it, the more their bottom lines benefit.

    • razibkhan

      well, most churches don’t (mainline + catholic). and most teachers have issues with no child left behind (it puts an unrealistic set of expectations upon them).

  • Robert Ford

    This position satisfies both the anti-corporate and anti-discrimination parts of The Narrative.
    Also, is biological development truly random? Or have we simply yet to find the genes that neutralize genes of strong effect? Are we perceiving complexity a randomness?

  • Dmitry Pruss

    I was listening to a radio interview the other day, with an author of a recent book on adoption whose name escapes me at the moment. He was asked why adoptees look for their birth parents. The answer was stark, “it’s just the useless human curiousity, common not just to the adopted children but to all of us”. Like, look at the genealogy craze around us! After expounding how looking for one’s biological roots is “normal and unimportant” (rather than a mean-spirited quest to reduce the standing of the adoptee’s “real parents”), he allowed that “sometimes, rarely, it’s important to know your biological family, because of family history of grave diseases like cancer”.

    Then it dawned on me that many people must consider genealogy, and genetic genealogy, as a shameful hobby, as an immoral attempt to deny nurture’s supposedly overriding role. But they may be OK with engaging in shameful activities for medical indication. Studying heritable traits is akin to proctology to them, not a table topic but alright if needed to stop diseases.

  • Luis Aldamiz

    You are obviously right: both nature (genetics, partly inheritable epigenetics) and nurture (pure epigenetics, other effects) do matter. The sheet is not blank but it also has a lot of space to write the end of the story in most cases.

    “Why does the discovery of an Ashkenazi genetic background transform Neo-Nazis into Jews in an ideological sense?”

    Not sure why you even ask this: it has to do with the extremist racist essence of Nazism: a Jew cannot be a Nazi, at least not in the classical sense and not in Europe or other white-dominated society. Nazism is all about “race” understood in a purely biological-genetic sense. Probably Hitler himself would have been kicked out of the Nazi Party and sent to a concentration camp if modern genetic tests would have been available in the 30s or 40s, because, we know now, he carried the African-ancestral patrilineage E1b (possibly because his unrecognized father was a Jew, although this is not 100% certain it fits well with his mother’s biography, who worked for a wealthy Jewish family until she became pregnant of Adolf).

    Nazis + genetic testing = very disturbing stuff, like the leader of the paramilitary Hungarian Guard (part of the Nazi party Jobbik), Szegedy being kicked out after discovering his Jewish ancestry.

    Quite obviously, if you are spousing by heart an antisemitic or otherwise ultra-racist discourse and you happen to discover that you actually belong in some degree to the stigmatized group, you life has to change and your “comrades” won’t welcome you anymore as one of them (if they don’t kill you right away).

  • Gary W Miller

    An improved understanding of our environmental exposures would be very beneficial. Schizophrenia certainly has a strong genetic component, but there is no doubt that external forces are at play.

  • ohwilleke

    Part of the zietgeist reflects the state of the research.
    * There are hundreds if not thousands of dieseses and physical conditions for which a genetic basis and biological mechanism has been more or less definitively determined. When you genuinely find a single gene recessive physical condition (or easier yet, a single dominant gene condition) medical science really nails it. These kinds of gene associations are quite easily to sluth out. The fact that lots of other gene associations for physical conditions are mushier (e.g. breast cancer risk enhancement) and more like cognitive traits in our level of understanding, is obscured by the ready supply of available clearly understood counterexamples. For example, my wife has a single gene recessive trait physical condition that is well understood and easy to understand the genetics of and see demonstrated in her extended family. Lots of people have had that experience. Those kinds of clear cases inflate the credibility of the entire field even though many examples of genotype-phenotype connections are muddier.
    * We aren’t there yet in cognitive traits. Many psychological traits and conditions are generally measured and defined by nothing more accurate than self-reporting on paper and pencil surveys in routine clinical and research practice. We have heritability estimates for various behavioral traits, but no firm biological basis, mechanism, or even consensus definition of many of the same psychological traits and conditions. Even in the case of well defined and heavily studied DSM-IV psychiatric conditions with known genetic causes and extensive genomic studies, like schizophrenia – family history is still a better predictor clincially than genetic testing. The macrostructure of personality and psychiatric conditions, which classifies by symptom in the absence of available etiology, has not been connected in theoretical architecture to the handful of genes that have been tagged as playing some role in our cognitive genotype. The lack of a coherent theory of cognitive phenotype causation and the know fact that some cognitive phenotype features (for example, the language you speak) are environmental in origin, gives nuture more staying power.
    * Feedback effects matter too. If you have congential Type I diabetes, there is no benefit to you from believing that it, like Type II diabetes, was caused by you or your parents eating habits. But, in a wide variety of cognitive endeavors with a signficant genetic component, even a mostly counterfactual belief that performance is all nuture and not nature is often the attitude that leads to the highest performances whatever actual genetic endowment you may have in that domain. Even if effort is only 10% responsible for how well you do in history, and inherited IQ is 90% responsible, people who believe that its all about effort are more likely to make the most of the 10% of the outcome that is within their control. This is true in a wide variety of endeavors so the extra attention to what you can control on the margins adds up. Thus, factually inaccurate beliefs can still be adaptive.

    • razibkhan

      the second clause is a lot of rhetoric.


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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


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