There has been a lot of attention to Erika Check Hayden’s piece Ethics: Taboo genetics, at least judging by people commenting on my Facebook feed. In some ways this is not an incredibly empirically grounded argument, because the biological basis of complex traits is going to be rather difficult to untangle on a gene-by-gene basis. In other words, this isn’t a clear and present “concern.” The heritability of many behavioral traits has long been known. This is not revolutionary, though for cultural reasons may well educated people are totally surprised when confronted with data that many traits, such as intelligence and personality, have robust heritabilities* (the proportion of trait variation explained by variation in genes across the population). The literature reviewed in The Nurture Assumption makes clear that a surprising proportion of contribution any parents make to their offspring is through their genetic composition, and not their modeled example. You wouldn’t know this if you read someone like Brian Palmer of Slate, who seems to be getting paid to reaffirm the biases of the current age among the smart set (pretty much every single one of his pieces that touch upon genetics is larded with phrases which could have been written by a software program designed to sooth the concerns of the cultural Zeitgeist). But the new genomics is confirming the broad outlines of the findings from behavior genetics. There’s nothing really to see there. The bigger issue of any interest is normative; the values we hold dear as a culture.
From what people tell me IQ is a social construct which is totally controlled by environmental variables, and so is not of much interest. But curiously the other day when I looked at the hits on this website over the past 3+ years a huge number of highly accessed posts had to do with intelligence and IQ. In any case, seeing as how many readers of this weblog are having, or going to have, children at a relatively advanced age (in an evolutionary sense) I thought this post would be a good public service announcement. Below is a figure from a preprint posted on arXiv, The effect of paternal age on offspring intelligence and personality when controlling for paternal trait level (via Haldane’s Sieve):
The Philadelphia Inquirer has a long piece which reports on the reality that the ‘crack baby epidemic’ of mentally retarded or unstable individuals turned out to be unfounded. The experimental design is as simple as can be: compare individuals of similar socioeconomic background, and track them over their lives. The past generation since the 1980s crack wave has been an unfortunate, yet illuminating, ‘natural experiment.’ The researchers found that contrary to expectations there are basically no statistically significant differences between ‘crack babies’ and control individuals.* This is not a surprising result, as there were hints of this in the child development literature even in the 1990s. The author of the study focused on a sample of lower class black Americans, and noted that despite the lack of statistical differences in outcomes due to exposure to crack in utero, these individuals have been exposed to a lifetime of an underclass milieu, which is likely not conducive to human flourishing. In other words, the reality is much more banal and unsurprising when viewed in a broader light.
It’s been about a year and a half since I officially became a father. I put the official qualifier there because I knew I was going to become a father about two years ago, and many of the psychological changes probably began then. My own reflections and lessons are obviously influenced by my own specific situation. I am not the primary caregiver. It would be too pat to say that our family is the typical college educated sort in all its details, but it is not that far from the truth. My daughter, and her parents, have resources, both financial and familial, which are not there for about half of Americans. I obviously can’t speak to the struggles of working class single mothers. And the American class system being what it is I can’t say I know any such women very well beyond the level of tenuous acquaintanceship.
A few years ago Malcolm Gladwell made the “10,000 hour rule” famous in his book Outliers. In practice (e.g., discussions with people day to day or on this blog) the rule gets translated into the inference “practice is what matters.” When talking about genetics this often implicitly also entails that “genes don’t matter.” I’m not saying that this is necessarily what Gladwell’s own exposition taken literally would suggest, but ideas have a way of evolving once they’re outside of the pages of a book.
My own response is that this sort of rhetorical device is silly. In domains of virtuosity the intersection of innate talent and conscientiousness are often critical. That’s because for outstanding excellence gains on the extreme margin of performance are critical. There are many born with talent, and those who hone and refine that talent will have an edge over those who do not exhibit the same work ethic. But the converse is that there are those born without talent for whom 10,000 hours of invested effort is lunacy.
In 2002 I read The Blank Slate. With all due respect to Steven Pinker one of the most fascinating aspects of this book was actually a review of the work of another psychologist, Judith Richard Harris. Harris’ own views are explicated crisply in The Nurture Assumption. In it she reviews and expands on a major insight from behavior genetics: over the long term parental influence seems to be a relatively marginal predictor in terms of many behavioral traits. To be explicit, one can imagine a personality trait which varies in the population. The variation of genes may explain 40% of the variation of the trait. The variation in parental child-rearing techniques, “shared home environment,” may explain 10% of the variation of the trait. The remaining 50% of the variation may be “non-shared environment.” That basically means we don’t have a definitive explanation of what the 50% remainder is, though Harris posits that this consists to a great extent of peer groups.*
In Slate there is an important piece up, The Early Education Racket, which attempts to reassure upper middle striving types that it isn’t the end of the world if their children don’t get into the right preschool. It is important because there are many people out there with lots of money (or perhaps more accurately, just enough money) and no common sense. Though the author, Melinda Wenner Moyer, offers that she’s not “making a Bell Curve argument here,” the general thesis that there are diminishing returns to inputs on childhood environment is well known to anyone with a familiarity with behavior genetics. Here’s a piece in Psychology Today from 1993, So Long, Superparents:The limits of parental influence: Why good parentsneed not attempt superhuman feats:
Now comes the insult. “Good enough” parents do the child-rearing job just as well as superparents, claim psychologists Sandra Scarr, Ph.D., and David Rowe, Ph.D. Middle-class parenting styles vary significantly, but the kids all turn out okay regardless of most differences, say the respective University of Virginia and Arizona professors.
Abusive and neglectful parents crank out problem kids who later become delinquent adults. But as long as kids get parental warmth, care, and encouragement to develop their talents, they have an equal shot at success in school and work. What really counts is the emotional and physical security parents can provide.
People pay a lot of attention to nuances in parenting style-how much parents hug their kids in public, whether or not they buy their kids an abacus. But they should pay more attention to genes, says Rowe. Inheritance is more important than many realize.
If you are doubtful of this, I recommend you read The Nurture Assumption. This book was published in 1999, and Steve Pinker reported on the results in The Blank Slate a few years later, where I first encountered the thesis. The basic insight, that parental home environment seems to have minimal predictive power in explaining variation in outcomes, is still not very well known. The two primary issues to keep in mind are:
Over at National Geographic David Dobbs of Neuron Culture has an eminently readable and engrossing piece up, Restless Genes. I have never really read about ‘allele surfing’ on the wave of demographic expansion in the way that Dobbs’ rendered it. I certainly wouldn’t have been able to produce that sort of spare but informative prose.
On Twitter there was some concern about the focus on DRD4. The issue is a general one in much of behavioral genomics, and I’m not too interested in rehashing the point. But the broader question of heritability of behavior remains. It seems to me that we have some ‘natural experiments’ now. For the past 50 years there have been a series of cross-cultural adoptions from Asia to North America and Europe. If human behavior variation across and within populations is substantially heritable than this might be a good place to start. Rather than focusing on genes, we need to focus on heritability first.
In The New York Times David P. Barash writes about how parasites might influence our behavior. This should not be too shocking an idea to readers of this weblog, I’ve blogged about Toxoplasma gondii before, on which there has been a raft of publications over the past 10 years or so. My main issue is that like much of behavior genomics I wonder about the possibility of any terminus and conclusion to this line of inquiry (as opposed to being fodder for high publicity publications indefinitely). For any given personality trait we know that a small proportion (on the order of 10 percent) of the predicted variation within the population is due to variation in family environment (i.e., the impact of parent-specific choices). Of the remaining fraction it is about evenly split between genetic effects (i.e., the genes you inherit from your parents, and the consequent dispositions) and “other/non-shared environmental effects.”
The thread below on the possibility of pedophilia being a biologically mediated tendency rapidly degenerated, to no one’s surprise. As I didn’t have the time to engage in strict moderation I had to close it. And I don’t want to reopen that particular topic. Rather, I want to focus on the issue of psychopathy exhibiting some genetic disposition.
I want to assert immediately that I’m not positing that you’re born a psychopath like you’re born with red hair. Rather, psychopathy is a set of traits whose upstream causes can be both genetic and non-genetic. In fact some cases of psychopathic behavior seems to be rooted in extreme social and psychological deprivation (e.g., orphanages in underdeveloped countries). Interestingly, this may be a case where the environmental input reshapes the developing brain, so that even though the individual may lack a genetic predisposition toward a particular psychology, they may now be biological oriented toward all the traits associated with psychopathy because of the nature of their neurological development.
Gawker published a piece on the neurological problems which might result in pedophilia, and naturally a lot of shock and disgust was triggered. The piece is titled Born This Way: Sympathy and Science for Those Who Want to Have Sex with Children. This isn’t something you want to click through to lightly. So fair warning. The neurobiological material did pique my interest:
“There was nothing significant in the frontal lobes or temporal lobes,” says Cantor. “It turned out the differences weren’t in the grey matter. The differences were in the white matter.”
“The white matter” is the shorthand term for groupings of myelinated axons and glial cells that transmit signals throughout the gray matter that composes the cerebrum. Think of the gray matter like the houses on a specific electricity grid and the white matter like the cabling connecting those houses to the grid.
“There doesn’t seem to be a pedophilia center in the brain,” says Cantor. “Instead, there’s either not enough of this cabling, not the correct kind of cabling, or it’s wiring the wrong areas together, so instead of the brain evoking protective or parental instincts when these people see children, it’s instead evoking sexual instincts. There’s almost literally a crossed wiring.”
The good news, according to Cantor, is that it if they can figure out how the wiring gets crossed, they might be able to suggest ways pregnant mothers can help ensure their baby is unlikely to be born a pedophile. “It is quite possible that one or more components of the process are related to prenatal stresses like poor maternal nutrition, toxin exposure, ill health, or poor health care,” he says. “If so, then improving health and health care in general may reduce the numbers of people vulnerable to developing pedophilia, as well as other problems.”
Trends in Genetics has a review article, The genetics of politics: discovery, challenges, and progress. The main reason I point to these sorts of papers isn’t that I think they’re revolutionary. Usually they aren’t. Rather, the public domain has totally forgotten about this domain of study. Most of the informed and high-toned discussion presumes that almost everything of worthy note is socially constructed. If not, then the counterpoint is a crude caricature of genetic determinism which is refutable in a blink of the eye. It’s as if someone was commissioned to paint R. Daneel Olivaw, and ended up using crayon to sketch out the Frankenstein monster.
For example, in sex differences the public debate veers between evolutionary psychological Leave It To Beaver, pre-scientific cultural traditionalism, and de facto Blank Slatism. On the one hand you have to deal with people who use “scare quotes” around the “highly speculative” “hypothesis” that males have a greater tendency toward inter-personal physical aggression than females (including in the comments of this blog, so spare with lectures about how this is a marginal perspective; I’m pretty sure I talk to people about behavior genetics a lot more than you do, though if not I’d like to hear from you!). Set against this you have an elevation of a particular specific and historically contingent nuclear family structure in the post-World War II West as normative by the laws of biology. Never mind that you need to leave the hearth to gather, and that someone must have been minding the farm when citizen soldiers were away at war. Some aspects of the ideal of American social conservatives may actually be socially constructed and economically contingent, rather than being a consequence of the natural laws of society. And just because something is socially constructed does not mean that it is not good or worth defending. And just because you believe that something is natural does not mean that you think that one should never rein in one’s natural impulses. Is and ought are not the same, and they do have relationships, but they’re complex and need to be teased apart precisely. As it is most discussions deal in rhetorical preening and misrepresentation of one’s interlocutors.
The above figure is from a paper I stumbled upon, Genetic and environmental influences on impulsivity: a meta-analysis of twin, family and adoption studies:
Virginia Hughes has an important post up at The Last Word on Nothing, What Americans Don’t Get About the Brain’s Critical Period. In it she reiterates just how stupid the “Baby Einstein” culture is. The post is important to me specifically because I have a baby who I would like nudge in the direction of Einstein, but not by spending money on toys which exist mostly to salve the vanity and conscience of adults around her. With all that said, Hughes emphasizes that the key is to focus on children at the other end of the environment spectrum from my awesome one.
So I was prompted by her post to check out the links, as I’ve not explored this literature in a while. First, Variation in neural development as a result of exposure to institutionalization early in childhood compares Romanian orphans who were kept in that nation’s notoriously atrocious orphanages and those who were fostered. The authors assert that the placements of the latter were randomized, and the neurological differences were significant. I doubt this is that surprising to most. Romanian orphanages have rightly become a byword for childhood deprivation.
Most of these stolen children were entrusted to the care of Catholics loyal to the regime. The aim behind this was to rid an entire people of the “Marxist gene,” at least according to the theories of Antonio Vallejo-Nájera, the national psychiatrist of Francoist Spain, that were widespread at the time.
More accurately it should be Marxist meme. But it brings up the question of looking into the correlation between the traits of biological parents and their long-lost children.
As a father the content of my conversations with friends and acquaintances has changed somewhat. Whereas in my offline life discussions of behavior genetics rarely came up, now they loom large implicitly and explicitly. Though the vast majority of people I interact with have graduate degrees or are pursuing graduate degrees in the life sciences almost none of them are aware of the magnitude of the heritability of most bio-behavioral traits.
For those of you who forgot, heritability is a population wide statistic which assesses the proportion of variation in the population you can attribute to heritable genetic variation. So if heritability is 1.0 all of the variation is due genetic variation; offspring are just a linear combination of their parents. If heritability is ~0.0, then there’s basically no correlation between parents and offspring. Though, as I said, heritability is a population-wide statistic, it can be informative on an individual level. For example, the heritabiilty of height is ~0.90 in the Western world. To give you a sense of the expected height of the offspring of two individuals, just take the average (in sex-controlled standard deviation units) and shift it back toward the mean by 10%. There is going to be a lot of variation around this average. The rule of thumb seems to be that the standard deviation across siblings is roughly similar to the standard deviation within the population (though it seems to be a bit lower, with sibling I.Q. deviations being 2/3 of the magnitude of population-wide deviations).
Below the fold is a table reproduced from the paper Genetic Influence on Human Psychological Traits A Survey. Please do not read the table as a gauge of the “geneticness” of the trait. (whatever that means) Rather, it should give you a rough sense of the “pull” that biological inheritance will have on an individual. Biology may not be destiny, but it is definitely probability.
As a follow-up to my post below, I just wanted to check some recent literature on crime and heritability. I found this, Heritability, Assortative Mating and Gender Differences in Violent Crime: Results from a Total Population Sample Using Twin, Adoption, and Sibling Models:
Research addressing genetic and environmental determinants to antisocial behaviour suggests substantial variability across studies. Likewise, evidence for etiologic gender differences is mixed, and estimates might be biased due to assortative mating. We used longitudinal Swedish total population registers to estimate the heritability of objectively measured violent offending (convictions) in classic twin (N = 36,877 pairs), adoptee-parent (N = 5,068 pairs), adoptee-sibling (N = 10,610 pairs), and sibling designs (N = 1,521,066 pairs). Type and degree of assortative mating were calculated from comparisons between spouses of siblings and half-siblings, and across consecutive spouses. Heritability estimates for the liability of violent offending agreed with previously reported heritability for self-reported antisocial behaviour. While the sibling model yielded estimates similar to the twin model (A ≈ 55%, C ≈ 13%), adoptee-models appeared to underestimate familial effects (A ≈ 20–30%, C ≈ 0%). Assortative mating was moderate to strong (r spouse = 0.4), appeared to result from both phenotypic assortment and social homogamy, but had only minor effect on variance components. Finally, we found significant gender differences in the etiology of violent crime
A = additive genetic variance component
C = shared family environment
This table from the paper shows the influence of study design….
The American culture promotes personal responsibility, the dignity of work, the value of education, the merit of service, devotion to a purpose greater than self, and, at the foundation, the pre-eminence of the family.
The power of these values is evidenced by a Brookings Institution study that Senator Rick Santorum brought to my attention. For those who graduate from high school, get a full-time job, and marry before they have their first child, the probability that they will be poor is 2%. But, if those things are absent, 76% will be poor. Culture matters.
I’ve been ragging on the cultural Left on this weblog recently because of the delusions that those of this bent simply won’t let go of in the quest for utopian egalitarianism. But one aspect of the American cultural and political scene is that Left and Right often operate with similar presuppositions, only weighting the emphasis differently. While the cultural Left puts the focus on nearly infinite possibilities of individual self-actualization, the cultural Right has backed itself into a corner of individual moral perfectionism which borders on the farcical.
In the comments below Nathaniel Comfort asks:
What I do, as a historian, is take something apparently simple and make it more complicated. I wonder about how your curves, e.g., would be applied in real life. *Specific* couples, *particular* children–individuals, cases, persons, context.
I’m asking things like:
-What would your hypothetical psychopathic lovebirds do with that information?
Comfort is referring to this figure I generated, which shows the potential distribution of outcomes for two individuals who tend toward more psychopathy than the general population. It seems to me that this question is easily answered if simply replace “psychopathy” with “odds for heart disease.” Endophenotypes aren’t magical, they’re just sometimes hard to characterize. But once you get a good grip on them you can make standard quantitative genetic predictions. One of the points I wasn’t clear about in the chart is that I assume that the “trait” being measured is the tendency toward psychopathy as measured by a paper & pencil test in one’s youth. This does not entail that an individual in fact behaves like a psychopath. Rather, it simply implies that they’re odds of behaving like a psychopath as an adult are highly elevated. I can’t find the link, but there was a story (which I blogged) a few years ago about a scientist who was studying the peculiarities of psychopath brain structure…and found out that he himself exhibited the same morphology typical of a psychopath. The point is that changing the odds or loading the die does not entail that an outcome is determined.
For example, imagine that you have a long family history of alcoholism. You marry another person with the same history. This sort of thing is heritable, and you’ve just loaded the die for your children. How can you try and compensate? I can think of one simple strategy: convert to a cohesive religious group which bans alcohol consumption, such as Mormons or Salafi Islam. The key here is that the social group is the environment. One can’t likely change that given any environment one’s children are more likely to be alcoholics, but the basal odds are shifted a great deal if you go from being a Catholic to a Mormon.
Also, as a new parent, one thing that I have realized is that behavior genetic understanding of human nature is very useful, it tells us that “attachment parenting” is pretty much crazy. Really more of costly signalling for upper middle class couples than anything else (though less crazy than the 18th century French middle class craze for country wet-nurses which resulted in incredibly high infant mortality rates). Being raised in a Romanian orphanage fucks you up. Your parents, not so much. The “nature vs. nurture” debates are going to continue indefinitely. But parents are will continue to matter less on a day to day level than they think in relation to the outcomes of their children. You can get to set the ground-rules, but there’s no way you will dictate the game.
A few days ago Nathaniel Comfort pointed me to this post, Genetic determinism round-up. If you are curious go read Comfort’s whole post. I honestly didn’t enjoy it very much, I think I got what he was saying, but there were all sorts of circumlocutions around the overall message. But I agree one one thing in particular: an emphasis on concrete and specific genes for traits is a motif in science journalism that can be very frustrating, and often misleading. Nevertheless, that’s not the only story. I believe our current culture greatly underestimates the power of genetics in shaping broader social patterns.
How can these be reconciled? Do not genes and genetics go together? The resolution is a simple one: when you speak of 1,000 genes, you speak of no genes. You can’t list 1,000 genes in prose, even if you know them. But using standard quantitative and behavior genetic means one can apportion variation in the population of a trait to variation in genes. 1,000 genes added together can be of great effect. The newest findings in genomics are reinforcing assertions of non-trivial heritability of many complex traits, though rendering problematic attributing that heritability to a specific set of genes.