Genetics, Science
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Heritability and why Parents (but not Parenting) Matter

“…Who in the world am I? Ah, that’s the great puzzle.”

— Alice from Alice’s Adventures in Wonderland by Lewis Carroll

Like Alice, we’ve all pondered the question: “who am I?”  Moreover, we often couple it with the reasonable companion query: “how did I get to be this way.”  Not all of us are rich and famous, we can’t all bend guitar strings like Hendrix, and most of us will never have supermodel looks or the physical prowess of a professional athlete.  There is fascinating unity in all of us, though, concerning how we answer the question of “why am I this way” as opposed to some other possible version of myself.  Whether we credit them for our successes, or point at them as a hurdle that we had to clear, most of us implicate our parents when constructing a narrative about why we are the way that we are.  It’s not an unreasonable intuition.  But how we intuit about the world can mislead us; sometimes that “light at the end of your tunnel” is, in reality, “just a freight train coming your way.”*1 To be blunt, most of what you think you know regarding why parents matter is very likely wrong.

You are the product of precisely two biological parents (even the so-called, “three-parent babies” are somewhat of a misnomer).  Whether you know them or not, whether you like them or not, the fact that you have parents (and were, in fact, not cloned from a prior version of yourself) carries with it great consequences.  Yet, family socialization effects on personality are not large, not prominent, and not pronounced (and for many traits, they are absent).¹ What parents do to their children (in particular, their style of parenting and efforts at socialization) does not leave permanent marks and does not differentiate individuals within the population for outcomes like intelligence, antisocial behavior, and a host of other outcomes.1,2,3 So why then, are parents consequential (beyond the obvious role that they play in providing safety, shelter, etc.)?  How do we rectify the apparent contradiction?

Let’s first discuss a term that has appeared frequently in our discussions: heritability. Heritability represents the proportion of variance in a particular trait that is explained by genetic variance within the population. As we’ve described before, heritability captures the role that genetic differences play in making some people (relative to others) taller or shorter, heavier or lighter, more intelligent or less intelligent, so on and so forth.1,2  Virtually every measurable trait (which varies within the population), we now know, is heritable.1  This reality has become remarkably unimpressive to many behavioral geneticists, though it continues to blindside some scientists who have managed not to pay attention for the last several decades.1,2,3  The shift among journal reviewers has been remarkable to witness, really, moving from: “there’s no way that trait X is heritable” to “of course trait X is heritable, who cares?” or even the more dubious (and disingenuous) “heritability is pointless, let’s talk about epigenetics [or gene-environment interaction]!”2,3 Changing sentiments aside, heritability continues to be an extremely relevant point for behavioral scientists to wrangle with.  Understanding why it is important, moreover, will take us a long way to understanding why parents (but not their parenting styles) are of such monumental importance in explaining variation in outcomes.

To complicate things just a bit, you should know that there are two types of heritability: narrow and broad sense.4 If you’ve ever heard the expression (perhaps from a plant or animal breeder) that a trait “breeds true” then you’re already informally acquainted with narrow-sense heritability.*2  Heritability in the narrow-sense captures variation that results from additive genetic influence.4 Heritability in the broad-sense includes other genetic effects which are non-additive (i.e., also in a technical sense, they can be non-linear).4 Imagine taking the effect of every gene that influences a trait—most of which would be very small—and adding them up; thus the term, “additive.”  Additive traits tend to breed true—meaning that variable characteristics manifest in the offspring in a similar (i.e., correlated) fashion to parents who possess such characteristics (at the population level and individual level).

Non-additive effects don’t breed true with the same degree of fidelity—in fact these effects bust up the clean transmission of traits from parents to children (to use a sports analogy, it’s a bit like a cornerback in football deflecting the quarterback’s perfect spiral aimed at the receiver).  Two brown-eyed parents can give rise to blue-eyed children, for instance.  Prior to Brother Mendel (just in case you weren’t aware, he was a monk) ever fiddling with his first pea pod (peas; the bane of all childhood existences), breeders were keenly interested in whether they could breed for certain traits.  Could you make the pigs fatter, or could you make the crops more disease resistant or drought tolerant?  If the answer was yes, then wealth and fame was surely in your future.  Knowing something about the narrow-sense heritability of a trait was important in that day and time, and it remains that way today.

We’re treading on delicate ground here because any time you start to talk about breeding, genetics, and (gasp) humans, it conjures up demonic specters.2,3 As if summoned from some regrettable Ouija board session, the ghastly ghoul of state-sponsored breeding programs comes barging into the room.  We’ll assume that we’re all in agreement regarding the moral repugnance of coercive eugenics, thus stipulating that such programs should never (ever, ever, ad infinitum) return.  The thing is, humans already have their own breeding initiative, and they have for some time now.  If you don’t believe us, consider for yourself how you picked a mate.  Did it happen to be at random? No?  What possibly could have gone wrong with that approach?  Think about it another way; say that you signed up for a high dollar dating service.  After several dud dates, and a subsequent phone call with customer service, would you be pleased to find out that your dates were being picked by the complex matching algorithm known as flinging darts against a wall with photos tapped on it?  If your answer is yes, then please stop reading and let’s get you signed up for: www.Boutwell-KhanDatingServices.com; our motto is: We throw darts as randomly as anyone, and we offer coupons!

Individuals discriminate on a range of qualities when searching for a mate.5,6  Even arranged marriages can’t get around this reality.  The difference with arranged marriage, of course, is that it is often a more “collective process”, with parents exhibiting increased control and discernment (perhaps more than the newly betrothed would like).  Regardless of who does the choosing (parents or children), it isn’t done haphazardly.  The qualities of emphasis might vary in some situations (for instance, whether the goal is short term liaison versus long term partnership, it might dictate what one is willing to tolerate in a partner)5 but the process is still far from random.  The qualities that humans prefer in their mates (what men look for in women and vice versa), moreover, are remarkably consistent across cultures.  There has been some excellent work on this topic carried out by evolutionary psychologists.5,6  Why does any of this matter?  Remember the issue of “breeding true”; well it applies to humans just like it applies to pea plants.  First, though, we need to talk more about sexual (and artificial) selection and foxes.

Famed biologist Richard Dawkins noted in his enjoyable (and important) book “The Greatest Show on Earth,7 that sexual (and artificial) selection offers powerful evidence in favor of Darwin’s arguments about natural selection.  It certainly does, and conveniently for our purposes, it also provides a very useful bit of insight.  Consider the landmark and very famous work (highlighted by Dawkins) carried out on the selective breeding of foxes.8 The goal of the work, in large part, was to better understand the processes of animal domestication. Foxes displaying high levels of tameness (when around a human) were bred with each other.  As it turns out, if you continually cross one tame fox with another, what you eventually get is an animal that starts to act (and even look) more like a dog than a fox.7,8  “Humans are not foxes!” objects the incredulous critic. True, but we don’t get to play by different rules (apologies to our creationist friends [and sadly, to many sociologists*3]).  The same evolutionary processes that apply to the fox and the hound (and every other organism on the planet), apply to us.7,8

Now we are getting more to meat of the issue.  Only a few pieces of information are needed to know something about what is likely to happen to a quantitative trait over time that is selectively bred for in a population.9 All that you need is the narrow-sense heritability of the trait (h2), the mean for trait (or the average value of the trait in the population), and the values possessed by the parents on a certain trait, and you are in business.9 Positive assortment for an extreme value in a trait that is highly heritable  (e.g., tall people pairing up with other tall people) is a mechanism for altering the distribution of values for that trait in the population.  You obtain a greater number of very tall people (thus, shifting the mean for height upwards)!  This is largely why parents matter, and this is also why knowing something about the heritability of a trait remains important (see Boutwell’s first essay on the topic of parenting for a more methodological treatment of why h2 is relevant).

Consider an example that dovetails with the previous point.  Criminologists (and psychologists) have been aware for some time that criminal involvement runs in families*4 and is also heritable (a good portion of that heritability seems to be narrow-sense, though not all; see quillette.com/#comments).  The psychologist Robert Krueger and colleagues10 some years back, provided evidence that humans mate assortatively for antisocial and criminogenic behaviors (put differently, highly antisocial individuals tend to pair off with each other in a non-random fashion).  Does this completely explain the concentration of crime in certain families?  No.  Can it be safely ignored and assumed to be irrelevant?  No.  Just as narrow-sense heritability is a puzzle piece that can tell you something about where the distribution of a trait could be headed in a population, it also helps inform the question of why certain traits cluster in families.9

An observant reader will argue that heritability is not a fixed quantity; it is subject to change over time.  The finding that the narrow-sense heritability of most personality traits is about .50 (or slightly lower), for instance, does not mean that it has always been that way, or that it will always be that way.1 While true, this point doesn’t serve as the ammunition for refuting the relevance of narrow-sense heritability that some might think.  At any point in history, the environment might explain more (or less) of the variance in some trait.  Nonetheless, if that fact somehow negated the import of h2 then plant scientists and animal breeders should search for other ways to spend their time—breeding programs would be impossible (and they are not).  Now, if you listen even more closely, you can hear the murmur of critics ready to hurl the objection of “epigenetics” in our direction.  We knew it would come up; it inevitably does these days.  But you must never forget that epigenetics is not a “get out of jail free” card that grants us immunity or exemption from evolutionary processes.  It certainly does not make heritability obsolete.

If epigenetic effects are highly variable across generations, given that the statistical methods used by behavioral geneticists subdivide “environmental” effects from heritable effects, then epigenetics will be included into that parameter (i.e., one of the environmental parameters). Alternatively, if epigenetic effects are highly transmissible across generations, then they are to a large extent heritable (an important point in its own right that so many sideline enthusiasts gloss over).  This comes, of course, with the necessary caveat that strong environmental shocks can induce epigenetic changes.  Importantly, extant empirical research does not suggest (yet) that these sorts of heritable epigenetic dynamics are pervasive enough to be problematic for heritability estimates.  They likely exist, but they are the exceptions, not the rule.11

Over the course of two essays, I (Boutwell) have tried to walk you through a series of topics that I see as incredibly important in modern social science.  The first dealt with problems in social science research (genetic confounding).  The largest take away point was simply that you cannot trust most research because most of it does not control for genetic influences on the outcomes they study (and we know that these effects are pervasive).  The second essay dealt with the complexity of ferreting out a parenting effect among the bewildering complexity of gene-environment correlation and interactions.  I also introduced you to the idea that epigenetics is unlikely to be the savior that many thought it was guaranteed to be.  For the third installment, Razib and I have tried to illustrate a fundamental evolutionary point: heritability matters.  Once again using parents as an exemplar.

Parents pass genes to their children.  In a Darwinian sense, this is of incredible importance.  Darwin, the brilliant scientist, prescient about so much, was nonetheless unaware that genes were the “packets of inheritance” responsible for making parents and progeny similar to one another.  It took the “religious” devotion of a monk (Mendel) to drive that point home.  Regarding those genes, Richard Dawkins poetically pointed out that (p.20):

They are in you and in me; they created us, body and mind; and their preservation is the ultimate rationale for our existence. They have come a long way, those replicators. Now they go by the name of genes, and we are their survival machines.12

Granted, this is probably not the defense of parents that you wanted, but then again, we never promised to deliver (necessarily) what you wanted.  We did intend to provide a “big-picture” rationale for why parents matter and why heritability does too.  In that regard, there is no better way to make the point then evolutionarily.  Parents matter because they pass genes from their generation to the next; that’s a pretty big deal in our estimation.

If what you were looking for is an impassioned crusade for why a certain approach to parenting is essential to civilized society, you won’t find that here.  There are times when it is best to let go of the feelings that you have regarding how the world works. In many cases, your self-assurance regarding your knowledge on some topic affords you little protection from science (anyone joining up for the Flat Earth Society these days?).  Famed biologist Robert Trivers strained our intuitions about the nature of parenting years ago by pointing out that the interests of mom and dad are not always the same as their filial creation (their child*5).  Behavior genetic studies were the flood that further obliterated the dam (for some context as to how parenting effects can be reconsidered, see my previous essay How to Find a Parenting Effect).  Parenting styles in the normal range of variation simply do not shed much insight into why people differ.

So that you don’t depart this parenting trilogy feeling too upset, though, consider a final point.  Your parents are important to you.  Do you really need to tack on the qualifier that they molded you like a ball of clay?  In order for you to appreciate your parents, must it be the case that they injected your personality directly into your head?  They didn’t, they injected it into your DNA (lovely image, right).  Your environment outside the home, as well as pure luck and happenstance shaped it from there.  You can still love and appreciate your parents, though.  Not one thing must change.  So as not to break with tradition from our first two parenting discussions, we leave you with the insights of someone else.  This time, Paul Simon has the last word.

“Still, a man hears what he wants to hear and disregards the rest.”*6

 

Razib Khan is a writer and doctoral candidate in genomics at the University of California. Follow him on Twitter: @razibkhan

Brian Boutwell is an Associate Professor of Criminology and Criminal Justice at Saint Louis University. Follow him on Twitter: @fsnole1

 

*Footnotes

  1. Find us two other academics that can work Lewis Carroll and Metallica [No Leaf Clover] into the same discussion.
  2. See also; Pinker, S. (2002). The Blank Slate: The Modern Denial of Human Nature. New York: Viking.
  3. Horowitz, M., Yaworsky, W., & Kickham, K. (2014). Whither the blank slate? A report on the reception of evolutionary biological ideas among sociological theorists. Sociological Spectrum, 34(6), 489-509.
  4. For a striking example, see: Frisell, T., Lichtenstein, P., & Långström, N. (2011). Violent crime runs in families: a total population study of 12.5 million individuals. Psychological medicine, 41(01), 97-105.
  5. Trivers, R. L. (1974). Parent-offspring conflict. American zoologist, 14(1), 249- 264.
  6. Simon and Garfunkel; The Boxer

References

  1. Polderman, T. J., Benyamin, B., de Leeuw, C. A., Sullivan, P. F., van Bochoven, A., Visscher, P. M., & Posthuma, D. (2015). Meta-analysis of the heritability     of human traits based on fifty years of twin studies. Nature genetics, 47, 702–70.
  2.  Barnes, J. C., Wright, J. P., Boutwell, B. B., Schwartz, J. A., Connolly, E. J., Nedelec, L., & Beaver, K. M. (2014). Demonstrating the validity of twin research in criminology. Criminology, 52(4), 588-626.
  3. Wright, J. P., Barnes, J. C., Boutwell, B. B., Schwartz, J. A., Connolly, E. J., Nedelec, J. L., & Beaver, K. M. (2015). Mathematical proof is not minutiae and irreducible complexity is not a theory: a final response to Burt and Simons and a call to criminologists. Criminology, 53(1), 113-120.
  4. Plomin, Robert, John C. DeFries, Valerie S. Knopik, and Jenae M. Neiderhiser. 2013. Behavioral Genetics, 6th ed. New York: Worth.
  5. Buss, D. M. (1994). The evolution of desire: Strategies for human mating. New York, NY: Perseus.
  6. Buss, D. M. (1989). Sex differences in human mate preferences: Evolutionary hypotheses tested in 37 cultures. Behavioral and brain sciences, 12(01), 1-14.
  7. Dawkins, R. (2009). The greatest show on earth: The evidence for evolution. Simon and Schuster.
  8.  Belyaev, D. K. (1979). Destabilizing selection as a factor in domestication. Journal of Heredity, 70(5), 301-308.
  9.  Snustad, D., & Simmons, M. (2009). Principles of genetics. 5th ed. New York: John Wiley & Sons
  10. Krueger, R. F., Moffitt, T. E., Caspi, A., Bleske, A., & Silva, P. A. (1998). Assortative mating for antisocial behavior: Developmental and methodological implications. Behavior genetics, 28(3), 173-186.
  11. Moffitt, Terrie E., and Amber Beckley. Abandon twin research? Embrace epigenetic research? Premature advice for criminologists. Criminology 53.1 (2015): 121- 126.
  12. Dawkins, R. (1976). The selfish gene. Oxford: Oxford University Press.

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27 Comments

  1. Fantastic conclusion to this series! These articles are essential reading. I can only hope more people come to understand these vital points.

    A few quibbles:

    Yet, family socialization effects on personality are not large, not prominent, and not pronounced (and for many traits, they are absent).

    Actually, I would go a step further. Studies have shown that the effects of family environment are completely absent for most any trait or outcome examined. (The only exception is education attainment; but the effect of family environment remains absent for outcomes downstream of this, like lifetime income. See my post “The Son Becomes the Father” below.)

    Does this completely explain the concentration of crime in certain families? No.

    Well, the work of researchers like Amir Sariaslan has shown that none of the other putative explanations (like living in criminal neighborhood or poverty) can explain why crime runs in families. Indeed, their work has found that the association between crime and “bad neighborhoods” and poverty is completely genetically confounded:

    The impact of neighbourhood deprivation on adolescent violent criminality and substance misuse: A longitudinal, quasi-experimental study of the total Swedish population

    Childhood family income, adolescent violent criminality and substance misuse: quasi-experimental total population study | The British Journal of Psychiatry

  2. To parents:
    Twin studies usually find “no effect” of common environment on human behaviors, as the article explains. Just note: this does not mean that the parent can have *no* effect on the child – only that the common variation in parenting behavior in the population has miniscule effect. I assure you that if you were to repeatedly drill holes into your kids’ heads and neglect to feed them, they would suffer long-term cognitive defects! But these behaviors are essentially absent in western countries, so they explain no variance in behavior. Point being: don’t think you can just give up parenting altogether.

  3. How do you explain the impact on learning behavior apparently achieved by injection of money into a poor neighborhood(Orlando, Fla. neighborhood of Tangelo Park) by Harry Rosen if parenting does not have a determining influence on behavior ?

    • “money into a poor neighborhood”

      1) u said *neighborhood*

      2) also, one has to make a distinction between short-term and long-term effects. in the short-term parenting does result in a lot of change. it just seems over the long-term it seems to matter very little.

  4. green eyes says

    Well as an adoptee I have noticed the wide difference in personality and behavior from my adopted family and siblings.

    You can always verify the claimed effects in this paper by looking at adoption studies and seeing how the adopted children conform to there biological parents as opposed to adopted parents. Even better if , as in my case , they have siblings who are biologically related to the household parents. Traits such as height, IQ, income, education , personality, mental health etc.
    This will be more valid if you can test them as adults, when they have more control over there own environment, and therefore the effects of there genome become more, not less pronounced.
    Like all such studies it will only give you a rough estimate, even with a very large sample size. But you should predict -under the reasonable assumption this papers findings are true-that the adopted children will have non random variation in trait display from there adopted parents and that non randomness will pull in the direction of there biological parents.
    Children are rarely exactly the same height as there biological parents , but they will tend to cluster in a particular pattern around that height (yes you have regression to the mean so the pattern wont be truly random-if parents short , the offspring will be more likely to be taller , or vice versa). But adopted children should have trait clustering that pulls in the direction of there biological parents. (with a small amount of confounding due to regression to the mean-which if this could be measured and factored in would actually make the heritability estimates larger).
    So, if adopted offspring cluster non randomly in that direction( of the biological parents), then you can infer from the pull of the variation generated by biological affiliation the size of the genetic effect. If the biological parents are significantly better predictors than the adopted parents for predicting trait outcome , then its likely genes heavily influence that trait. Once again you would need very large sample sizes to get even roughly accurate estimates off this, but it would prove the conceptual point in this article at a minimum.

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  6. Brian, anyone else, this is a serious question, and the answer must be easy for a pro:

    “– someone tell me someone’s tried the opposite of the socialization researchers’ plan: assume that we are social animals, socialized by default, and search for the mechanics of antisocialization, which might be abuse and negative experience. Please?”

    The answer is either

    a.) “yes, obviously. See the work of X., and X., and X . . . ” Or it’s either

    b.) “no, but what a good idea! I’ll start right now!” or

    c.) “no, for these good reasons ; . . . ”

    anyone care to take a stab?

  7. Artem says

    It is interesting that an article purporting to describe the state of the field on cognitive development can go without citing a single paper from the field of, you know, cognitive development. “Geneticists find genetic effects” is not much of a story in itself, what is interesting is how these findings are assessed when taken in conjunction with findings like these: “http://onlinelibrary.wiley.com/doi/10.1111/j.1467-8624.1994.tb00777.x/abstract”, or in fact any number of articles on early intervention, actually, especially in cases where there is some sort of genetic problem.

    After all, if nobody speaks to the child, the child herself will not learn to speak. And if the child is deafblind, the type of “socialization” she undergoes suddenly becomes really important, as for her to learn speech and abstract thinking at all, a very special type of developmental interaction becomes necessary.

  8. skeptical dude says

    It’s hard not to think it’s overhyped BS to some degree. Akin to a bizarro-world version of an extreme “blank slate” notion.

    Your kid just want to eat candy, no healthy foods? Just play and no study? Just give up! It’s in their genes! (Yours as well, so you’re probably a fat lazy slob in denial). No point in trying to “teach” discipline, self-control, or develop it yourself.

    Makes it sound as if values don’t matter, experiences don’t matter (or somehow, just in so far as the parents are involved in the interaction), just chains of nucleic acids matter. Cultural changes over the decades, which wouldn’t presumably be due to genetic evolution, are somehow. Perhaps there is a whole host of otherwise harmless viruses, not “memetic” virus, but genetic virus of course, shaping societies’ values. Oh, wait, I’m saying “society”, so perhaps that’s somehow completely totally different thing than influences of life experience at an individual level. “The whole is bigger than the sum if its units”, making somehow a collective of individuals more significantly shaped by other things than their genes, but not individuals themselves.

    But perhaps it’s a extended phenotype kind of thing. So Americans are really genetically fatter than Europeans, it’s only that more recently they’ve effectively manipulated their environment so that it allows them to develop their true genotypical morbidly obese genotype. Similarly with all of the so-called “cultural” lefty blank slate HBD denier mumbo-jumbo stuff.

    Should there also be sequel to those articles, explaining how dog training is really just a politically correct delusion, and dog behavior is all 100% attributable to genetics, or, at most, the social influence of dog packs.

    I love how there always must be these preemptive ad hominems/well-poisonings, asserting that “denying” is just refusing to accept some harsh reality, according to some renowned person quoted, for added authority.

  9. Joseph Bleau says

    So, is condescending arrogance a heritable trait? Just curious if we need to blame your parents or your professors.

  10. A thousand years ago, virtually everyone on earth was poor. Today, billions lead lives of relative luxury, health and safety. Did genetics alone create such changes in the “human condition”? I doubt it. Ten centuries is not nearly long enough to result in such a wholesale, world-wide genetic changes.

    For example, the housing bubble burst just 8 years ago was in part brought on by putting people in homes they couldn’t afford, and lacked the values and skills (delayed gratification, foresight, savings habits, the drive to preserve their property, e.g.) that successful homeowners have. Did all the successful homeowners get that way because of their genes, or because their parents imparted those skills and values to them?

    And…just where *is* this successful homeowner gene?

  11. seems a little nuts. So, a baby raised in 21st century San Francisco will be the same as one raised in 21st century Detroit? Environment matters, just not sure how much. Doubt Bill Gates’s genes would have been awesome in 9th century Scandinavia, what with Viking invasions and all.

  12. To all Brian’s readers, heritability is a population statistic that can’t be applied to a) individuals and b) populations beyond the population from which the heritability estimate was derived.

    I’ll say that again: You cannot apply h2 (heritability) estimates to any population beyond the one you studied. Why..?

    Whether Brian is blissfully unaware of this fact or whether he ignores it, I’m not sure. Given that he has sat in (at least) a few undergraduate psych classes, I’m assuming the latter. This indicates that ideology, and not science is at play here.

    I thought we dealt with all this nonsense in the 80’s with the fallout from Murray’s awful ‘The Bell Curve’ urgh.

    • Sorry, I typed why without replying. Why? Because with a new population the genetic variability and environmental variability will be different.

    • Brian says

      I’m not sure if you simply didn’t bother to read what we wrote, or just chose to ignore it and comment anyway. Either way, we’re well aware of the point you mention. In fact, we said the following:

      “An observant reader will argue that heritability is not a fixed quantity; it is subject to change over time. The finding that the narrow-sense heritability of most personality traits is about .50 (or slightly lower), for instance, does not mean that it has always been that way, or that it will always be that way. While true, this point doesn’t serve as the ammunition for refuting the relevance of narrow-sense heritability that some might think. At any point in history, the environment might explain more (or less) of the variance in some trait. Nonetheless, if that fact somehow negated the import of h2 then plant scientists and animal breeders should search for other ways to spend their time—breeding programs would be impossible (and they are not).”

      • Simon says

        I may not have been clear but your reply doesn’t speak to my comment. I’m talking populations (aka samples) not changes in populations across time (which was the subject of your reply).

        To be clear, you can’t extrapolate h2 from a given population and then apply that h2 to another population.

        This is mainly because if there is less environmental variability h2 goes up, even if the contribution of genes is unchanged across samples (and vice versa).

        That is, if you do most of your research on homogenous samples, h2 will be high relative to research on heterogeneous samples despite the probable genetic contribution to phenotype being similar/same. (As an aside, this is why sampling bias is a big problem in genetic research).

    • No Gimp.

      As Brian pointed out, if additive heritability was rendered irrelevant by environmental changes then plant and animal breeders would be out of business. Since they clearly aren’t, that objection is nowhere as important as people who harp on it make it out to be.

      With regard to humans, it’s one of those things that’s technically true in theory: environment could modify heritability estimates. But there are few if any examples of this in practice.

      Indeed Gregory Clark’s The Son Also Rises established that heredity has been a factor is human achievement going back at least several centuries, and across many different human groups.

      Word of advice: before harping a theoretical objection, provide a real world example of it being a problem – especially when the thing you’re objecting to has such a robust base of evidence behind it like behavioral genetic does.

  13. Am I blocked? says

    Wow, I replied with my wife’s email and it worked. Not wanting to be paranoid but censorship of dissenting views is not cool….Gimp

    • Brian says

      There was also no point in which we claimed (in any article) that the findings could (or should) be extrapolated to each individual in the population.

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