Pinker on Nature "vs" Nurture

My Genome, My Self - Steven Pinker Gets to the Bottom of his own Genetic Code - NYTimes.com

"The human mind is prone to essentialism — the intuition that living things house some hidden substance that gives them their form and determines their powers...

During my first book tour 15 years ago, an interviewer noted that the paleontologist Stephen Jay Gould had dedicated his first book to his father, who took him to see the dinosaurs when he was 5. What was the event that made me become a cognitive psychologist who studies language? I was dumbstruck. The only thing that came to mind was that the human mind is uniquely interesting and that as soon as I learned you could study it for a living, I knew that that was what I wanted to do. But that response would not just have been charmless; it would also have failed to answer the question. Millions of people are exposed to cognitive psychology in college but have no interest in making a career of it. What made it so attractive to me?

As I stared blankly, the interviewer suggested that perhaps it was because I grew up in Quebec in the 1970s when language, our pre-eminent cognitive capacity, figured so prominently in debates about the future of the province. I quickly agreed — and silently vowed to come up with something better for the next time. Now I say that my formative years were a time of raging debates about the political implications of human nature, or that my parents subscribed to a Time-Life series of science books, and my eye was caught by the one called “The Mind,” or that one day a friend took me to hear a lecture by the great Canadian psychologist D. O. Hebb, and I was hooked. But it is all humbug. The very fact that I had to think so hard brought home what scholars of autobiography and memoir have long recognized. None of us know what made us what we are, and when we have to say something, we make up a good story.

An obvious candidate for the real answer is that we are shaped by our genes in ways that none of us can directly know...

In the 20th century, many intellectuals embraced the idea that babies are blank slates that are inscribed by parents and society. It allowed them to distance themselves from toxic doctrines like that of a superior race, the eugenic breeding of a better species or a genetic version of the Twinkie Defense in which individuals or society could evade responsibility by saying that it’s all in the genes. When it came to human behavior, the attitude toward genetics was “Don’t go there.” Those who did go there found themselves picketed, tarred as Nazis and genetic determinists or, in the case of the biologist E. O. Wilson, doused with a pitcher of ice water at a scientific conference...

Today, as the lessons of history have become clearer, the taboo is fading. Though the 20th century saw horrific genocides inspired by Nazi pseudoscience about genetics and race, it also saw horrific genocides inspired by Marxist pseudoscience about the malleability of human nature. The real threat to humanity comes from totalizing ideologies and the denial of human rights, rather than a curiosity about nature and nurture. Today it is the humane democracies of Scandinavia that are hotbeds of research in behavioral genetics, and two of the groups who were historically most victimized by racial pseudoscience — Jews and African-Americans — are among the most avid consumers of information about their genes.

Nor should the scare word “determinism” get in the way of understanding our genetic roots. For some conditions, like Huntington’s disease, genetic determinism is simply correct: everyone with the defective gene who lives long enough will develop the condition. But for most other traits, any influence of the genes will be probabilistic. Having a version of a gene may change the odds, making you more or less likely to have a trait, all things being equal, but as we shall see, the actual outcome depends on a tangle of other circumstances as well...

To study something scientifically, you first have to measure it, and psychologists have developed tests for many mental traits. And contrary to popular opinion, the tests work pretty well: they give a similar measurement of a person every time they are administered, and they statistically predict life outcomes like school and job performance, psychiatric diagnoses and marital stability...

The most prominent finding of behavioral genetics has been summarized by the psychologist Eric Turkheimer: “The nature-nurture debate is over. . . . All human behavioral traits are heritable.” By this he meant that a substantial fraction of the variation among individuals within a culture can be linked to variation in their genes. Whether you measure intelligence or personality, religiosity or political orientation, television watching or cigarette smoking, the outcome is the same. Identical twins (who share all their genes) are more similar than fraternal twins (who share half their genes that vary among people). Biological siblings (who share half those genes too) are more similar than adopted siblings (who share no more genes than do strangers). And identical twins separated at birth and raised in different adoptive homes (who share their genes but not their environments) are uncannily similar...

Behavioral genetics has repeatedly found that the “shared environment” — everything that siblings growing up in the same home have in common, including their parents, their neighborhood, their home, their peer group and their school — has less of an influence on the way they turn out than their genes. In many studies, the shared environment has no measurable influence on the adult at all. Siblings reared together end up no more similar than siblings reared apart, and adoptive siblings reared in the same family end up not similar at all...

The two traditional shapers of a person, nature and nurture, must be augmented by a third one, brute chance...

The environment... is not a stamping machine that pounds us into a shape but a cafeteria of options from which our genes and our histories incline us to choose...

All of us already live with the knowledge that we have the fatal genetic condition called mortality, and most of us cope using some combination of denial, resignation and religion...

Assessing risks from genomic data is not like using a pregnancy-test kit with its bright blue line. It’s more like writing a term paper on a topic with a huge and chaotic research literature. You are whipsawed by contradictory studies with different sample sizes, ages, sexes, ethnicities, selection criteria and levels of statistical significance...

For all the narcissistic pleasure that comes from poring over clues to my inner makeup, I soon realized that I was using my knowledge of myself to make sense of the genetic readout, not the other way around...

Individual genes are just not very informative. Call it Geno’s Paradox. We know from classic medical and behavioral genetics that many physical and psychological traits are substantially heritable. But when scientists use the latest methods to fish for the responsible genes, the catch is paltry.

Take height. Though health and nutrition can affect stature, height is highly heritable: no one thinks that Kareem Abdul-Jabbar just ate more Wheaties growing up than Danny DeVito. Height should therefore be a target-rich area in the search for genes, and in 2007 a genomewide scan of nearly 16,000 people turned up a dozen of them. But these genes collectively accounted for just 2 percent of the variation in height, and a person who had most of the genes was barely an inch taller, on average, than a person who had few of them. If that’s the best we can do for height, which can be assessed with a tape measure, what can we expect for more elusive traits like intelligence or personality?...

Though we know that genes for intelligence must exist, each is likely to be small in effect, found in only a few people, or both. In a recent study of 6,000 children, the gene with the biggest effect accounted for less than one-quarter of an I.Q. point. The quest for genes that underlie major disorders of cognition, like autism and schizophrenia, has been almost as frustrating. Both conditions are highly heritable, yet no one has identified genes that cause either condition across a wide range of people. Perhaps this is what we should expect for a high-maintenance trait like human cognition, which is vulnerable to many mutations...

The self is a byzantine bureaucracy, and no gene can push the buttons of behavior by itself. You can attribute the ability to defy our genotypes to free will, whatever that means, but you can also attribute it to the fact that in a hundred-trillion-synapse human brain, any single influence can be outweighed by the product of all of the others...

Even if personal genomics someday delivers a detailed printout of psychological traits, it will probably not change everything, or even most things. It will give us deeper insight about the biological causes of individuality, and it may narrow the guesswork in assessing individual cases. But the issues about self and society that it brings into focus have always been with us. We have always known that people are liable, to varying degrees, to antisocial temptations and weakness of the will. We have always known that people should be encouraged to develop the parts of themselves that they can (“a man’s reach should exceed his grasp”) but that it’s foolish to expect that anyone can accomplish anything (“a man has got to know his limitations”). And we know that holding people responsible for their behavior will make it more likely that they behave responsibly. “My genes made me do it” is no better an excuse than “We’re depraved on account of we’re deprived.”

Many of the dystopian fears raised by personal genomics are simply out of touch with the complex and probabilistic nature of genes. Forget about the hyperparents who want to implant math genes in their unborn children, the “Gattaca” corporations that scan people’s DNA to assign them to castes, the employers or suitors who hack into your genome to find out what kind of worker or spouse you’d make. Let them try; they’d be wasting their time.

The real-life examples are almost as futile. When the connection between the ACTN3 gene and muscle type was discovered, parents and coaches started swabbing the cheeks of children so they could steer the ones with the fast-twitch variant into sprinting and football. Carl Foster, one of the scientists who uncovered the association, had a better idea: “Just line them up with their classmates for a race and see which ones are the fastest.”

It is a question of the most perspicuous level of analysis at which to understand a complex phenomenon. You can’t understand the stock market by studying a single trader, or a movie by putting a DVD under a microscope. The fallacy is not in thinking that the entire genome matters, but in thinking that an individual gene will matter, at least in a way that is large and intelligible enough for us to care about.

If you really want to know yourself (and this will be the test of how much you do), consider the suggestion of François La Rochefoucauld: “Our enemies’ opinion of us comes closer to the truth than our own."


This reminds me of claims that because we haven't found a "gay gene", homosexuality cannot be genetically-linked.