so the mother of all meta-analyses of twin studies and the heritability of human traits was published the other day: “Meta-analysis of the heritability of human traits based on fifty years of twin studies” [pdf].
the authors looked at “17,804 traits from 2,748 publications including 14,558,903 partly dependent twin pairs, virtually all published twin studies of complex traits.” 14.5+ MILLION twin pairs! as james thompson said, this study pretty much represents “the mother of ‘F*** Off’ samples.” (~_^) in future, if someone says to you that twin studies were debunked a long time ago, blah, blah, blah, just point them to this paper.
and the upshot is: we are not blank slates. we never were.
from the paper, “[A]cross all traits the reported heritability is 49%.” in other words, these researchers found that pretty much half of the variance in all sorts of physical and behavioral traits in humans — the differences that we see between people — can be accounted for by genetics.
here’s a key table from the paper. i took the liberty of jiggling it around a bit so it would fit better on the blog (h2 is what you should be looking at here — that’s narrow sense heritabilty):
the press has picked this up as there being an even split between nature and nurture, genes versus “the environment.” here, for example, from the huffington post*:
“It’s an age-old debate: do our genes make us who we are, or is it the environment in which we were raised?
“There’s long been agreement that both ‘nature’ and ‘nurture’ play some role in determining many aspects of our physical and mental selves, from our height and weight to our intelligence and disposition. But as to which plays the bigger role in shaping us, scientists have never seemed to agree.
“That debate may now be over, thanks to a sweeping analysis of studies conducted around the world for more than five decades. The analysis — involving more than 14.5 million twin pairs from 39 countries — indicates that nature and nurture are virtually tied.
“Across all of our traits, in other words, genes and environment exert equal influence.”
yeeeessss…but what is “the environment”? on hearing that most people will think of things like reading bedtime stories to kids or playing mozart to your unborn fetus. but those sorts of things are decidedly not what the environment is in this context. from kevin mitchell of wiring the brain:
A plea to people doing twin studies. Stop using the word "environmental" when you just mean "non-genetic"! https://t.co/Sf6vxTGojY
— Kevin Mitchell (@WiringTheBrain) May 19, 2015
“Even the technical sense of ‘environment’ used in quantitative behavioral genetics is perversely confusing. Now, there is nothing wrong with partitioning phenotypic variance into components that correlate with genetic variation (heritability) and with variation among families (‘shared environment’). The problem comes from the so-called ‘nonshared’ or ‘unique environmental influences.’ This consists of all the variance that is attributable neither to genetic nor familiar variation. In most studies, it’s calculated as 1 – (heritability + shared environment). Practically, you can think of it as the differences between identical twins who grow up in the same home. They share their genes, parents, older and younger siblings, home, school, peers, and neighborhood. So what could make them different? Under the assumption that behavior is a product of genes plus environment, it must be something in the environment of one that is not in the environment of the other.
“But this category really should be called ‘miscellaneous/unknown,’ because it has nothing necessarily to do with any measurable aspect of the environment, such as one sibling getting the top bunk bed and the other the bottom, or a parent unpredictably favoring one child, or one sibling getting chased by a dog, coming down with a virus, or being favored by a teacher. These influences are purely conjectural, and studies looking for them have failed to find them. The alternative is that this component actually consists of the effects of chance – new mutations, quirky prenatal effects, noise in brain development, and events in life with unpredictable effects.
“Stochastic effects in development are increasingly being recognized by epidemiologists, frustrated by such recalcitrant phenomena such as nonagenarian pack-a-day smokers and identical twins discordant for schizophrenia, homosexuality, and disease outcomes. They are increasingly forced to acknowledge that God plays dice with our traits. Developmental biologists have come to similar conclusions. The bad habit of assuming that anything not classically genetic must be ‘environmental’ has blinkered behavioral geneticists (and those who interpret their findings) into the fool’s errand of looking for environmental effects for what may be randomness in developmental processes.”
“Just because some trait is not genetic does not mean it is not innate. If we are talking about how the brain gets wired, any number of prenatal environmental factors are known to have large effects. More interestingly, however, and probably a greater source of variance across the population, is intrinsic developmental variation. Wiring the brain is a highly complex procedure, reliant on cellular processes that are, in engineering terms, inherently ‘noisy’. Running the programme from the same starting point (a specific genotype) does not generate exactly the same output (the phenotype) every time. The effects of this noise are readily apparent at the anatomical level, when examining the impact of specific mutations, for example. In many cases, the phenotypic consequences are quite variable between genetically identical organisms, or even on two sides of the same brain. (If you want to see direct evidence of such developmental variation, take a directly face-on photograph of yourself, cut it in half and make mirror-image copies of the left and right sides. You will be amazed how different the two resultant faces are).
“If the way the brain is wired is determined, not just by the starting genotype, but, to a large extent by chance events during development, then it is reasonable to expect this variation to be manifest in many psychological traits. Such traits may thus be far more innate than behavioural genetics studies alone would suggest.“
in other words, it’s NOT genes + environment (or nature + nurture) — not as most people would think of it anyway. it’s genes + shared environment (which, since it’s shared, i.e. the same for the individuals in question, oughtn’t to make a difference, right?) + nonshared environment (which can include de novo mutations and development noise, which also may be heritable! iow, variation itself might be a genetic trait.). not much room for the effects of nurture here.
so, when you see a figure like 51% for “environmental” causes behind the differences we see in traits between people, remember that that very much includes biological causes like new mutations that are particular to individuals and developmental “noise,” which again may ultimately be regulated by genes.
h/t once again to jayman for cluing me in on this in the first place! (^_^)
*to give credit where credit is due, the huff post journalist did mention that part of what’s included in “the environment” is measurement error. that is correct. edit: see comment below about measurement error. so the 49% heritabilty figure should be considered a very conservative figure.
p.s. – there’s even a dedicated website where you can have a look at all the heritability numbers for yourself. enjoy!
previously: it’s not nature and nurture…
(note: comments do not require an email. the blank slate.)
you will never understand human biodiversity without first turning an hbd-eye on yourself.
before i elaborate on that, a small exercise. indulge me.
at the end of this sentence, when i ask you to, i want you to raise your eyes from your monitor (or smartphone or tablet or whatever device you’re using), glance around for a few seconds, and then come back here. okay: go!
now, i don’t know exactly what you saw during your brief adventure away, but what i do know is that when you looked around your room or office or the coffee shop or your own private tropical island (d*mn you!), you experienced seeing a smooth, undisturbed, flowing picture of your surroundings — it was a video-like experience (hopefully not a shaky cam-like one! if so, get to a doctor, quick!). that experience is a false one, created by your brain to make life easier for you. what happens, in fact, is that each and every time we move our gaze from one object or scene to another, in the intervening nanoseconds, we are effectively blind. we don’t “see” anything for those split seconds. the reason we don’t experience what would presumably be a very disturbing and confusing one — the lights going off and on all day long! — is because our brains fool us. the brain interpolates the visual data captured via eyeballs, etc., and presents it all to its owner (user?) in a nice, even — but unreal — picture of what that individual “sees.”
cool, huh? yeah.
the reason i bring this up is just to illustrate how our brains are not really to be trusted. fantastic, wonderful, unfathomable organ! — but one that fools us. a lot! it deceives us so that we don’t go around bumping into things all day long (the saccadic masking mentioned above). it deceives us (deceives itself!) so that we can decieve others. it probably fools each of us into believing that we are discrete individuals — that we are or have “selves.” h*ck! it even looks like our consciousness is not a stream but more like rhythmic pulses. all for good evolutionary reasons, of course. but, still, there it is: the brain is a trickster.
once you realize this about the human brain — that it’s an indispensible but untrustworthy organ — all of the cognitive biases and dissonances that we suffer from start to make sense. humans are not rational creatures. we are capable of some amount of logic and rational thought (some more than others), but more often than not, our “reason” serves as an excuse generator for our innate drives, desires, and proclivities.
the next thing you need to know — and you really have to internalize this — is that all of those drives and desires and proclivities are innate. all behavioral traits are heritable to some degree or another, which means that genes are behind them, and which means that there’s not much any of us can do to change our natures. for instance, there prolly aren’t specific genes that will make a person a christian versus a muslim, but there are definitely genes “for” religiosity. which religion a person with “genes for” religious belief follows will obviously depend to a large degree on the culture in which he is immersed, but persons with “genes for” religious belief will tend to be religious or spiritual somehow.
all behavioral traits are heritable. and, so, you cannot change people or peoples — not fundamentally. people are what they are. you are what you are, and so most of your thoughts and conclusions and feelings about life and the world around you are expressions of your innate traits. mine, too. (don’t worry. i’ll get to that.) and let’s be honest: innate traits and a deceiving brain are no foundations for uncovering the truth. we cannot rely on our gut instincts in trying to uncover the facts about reality or to (consciously) understand how the world works. the only way around this problem of our lyin’, cheatin’, no-good brains is to rely on science and its finding. of course, since science is conducted by humans, we run into all those cognitive biases, etc., again. but with enough effort, i think we can eventually discover some truths. either that or space stations will some day start falling out of the sky, and we’ll know we’re doing it wrong.
now back to my initial point: you will never understand human biodiversity without first turning an hbd-eye on yourself. first, learn this about yourself — that your thoughts and feeling and behaviors are heritable and largely out of your control — and then try to apply this knowledge to your understanding of other individuals and groups. examine your ideas and your feelings. your gut instincts (be especially suspicious of those!). your beliefs. you may think you have thought through the important questions rationally, but chances are you haven’t. not really. be honest with yourself. and be hard on yourself. but remember to have a laugh about it all, too — how absurd it all is really at the end of the day! (~_^)
remember my three laws of human biodiversity. and don’t ever forget that there are exceptions to the rules — and that you might be one of them — or your neighbor might. always — always! — keep in the forefront of your mind the concept of AVERAGE when you think about the human biodiversity between groups — and that not every member of a group will fit the average. do NOT pick and choose the areas of human biodiversity that suit your tastes and disregard the rest. you won’t get any dessert if you do.
most importantly — and i can’t emphasize this enough — do NOT project your innate feeling and thoughts and inclinations onto others! you might think and feel one way, but the other person sitting next to you might not. and he might really think and feel very differently from you, and have a completely different perspective on the world — different in a fundamental way — that neither he nor you can change, because he was born this way. (or maybe experienced a developmental insult that affected his biology in a similarly permanent sort of fashion.)
do not project your preferences onto other individuals or groups. just because you like to keep a super tidy house (you ocd person) doesn’t mean others do. and just because you and your people feel that living in nuclear families and having loose (or nonexistent) extended family ties is a nice way to live doesn’t mean that other peoples want that. and just because democracy happens to work well in your population — or autocracy, depending on where you’re from — doesn’t mean either of them would transfer well to other populations having different average innate characteristics from your own.
so, below are some aspects of human biodiversity you might want to run through when you’re getting to know thyself. there’s lots more. these are just some things i thought of off the top of my head. (if i were really organized, which i am not, i would’ve linked to how heritable each of these different traits is. maybe i’ll go back and fill those in one of these days. for now, you’re on your own — google ’em. or check jayman’s blog. he’s probably got a lot of the heritability figures over there! (^_^) ) try and see if identifying and recognizing any or all of your innate traits helps you to understand why you think and feel and behave in the ways that you do.
– are you male or female? men and women on average think and feel differently about an awful lot of things. don’t blame me. i’m just the messenger.
– are you heterosexual or homosexual? or some other sort of sexual? heterosexual men and women on average think and feel differently about quite a lot of things compared to gay men and lesbian women et al. and i don’t just mean about preferred sexual partners. remember that there are always exceptions to these rules. and remember not to PROJECT your thinking/feelings onto other subgroups here (yes, i am looking at you butch lesbian feminists!).
– what is your racial and, to my mind more interesting and important, ethnic background? what other sort of population or subpopulation might you belong to (eg. siberian peoples or sicilians)? are you a person of mixed heritage? plenty of average differences in all sorts of directions here.
– how intelligent are you? what’s your iq? try to remember that people of much lower intelligence than you will have a very hard time understanding a lot of the things that you do, and that you will find it difficult, if not impossible, to grasp the ideas and concepts that people more intelligent than you can. be humble (if you’re able).
– what personality traits characterize you? both big 5 and hexaco. are you open to experiences? people who score low on openness are generally conservative. are you conscientious? in other words, are you efficient and organized or more easy going and (*ahem*) disorderly? are you an extravert or an introvert? if you’re an extravert, you’re probably not enjoying this exercise at all. sorry. (in my experience, extraverts are not very introspective.) are you agreeable? kind, sympathetic, warm. or are you angry all the time? are you neurotic or emotional? or are you more stable? and from the hexaco scale, where do you rank when it comes to honesty-humility?
– how old are you? if you’re under, say, 24, keep in mind that your brain hasn’t finished developing yet. your frontal lobes are incomplete, so you’ve got very little sense. (~_^) if you’re a young male, between say 16 and 24, you might be quite aggressive (although not necessarily violent) and risk tasking. be careful out there! if you’re (*ahem*) older, remember that everything slows down with age. (sorry to remind you of that!) it does get harder to teach old dogs new tricks. and everybody, remember that, in general, each of us becomes more like our true selves as we get older, because we get to choose our preferred environments once we grow up.
– are you religious or areligious — or even irreligious? remember that religiosity/spirituality is highly heritable.
– are you conservative or liberal or something in between? or something more extreme? or apolitical? remember than political orientation is also highly heritable.
– are you an optimist or a pessimist? is the glass half full or half empty? are you a depressive, emo kid or are you one of those always-chipper people? again, all highly heritable.
– are you a follower or a contrarian? i haven’t seen much research on this (i know there is some, but i wish there was more), but i’d bet a ton of $$$ that these traits are highly heritable, too. prolly tie in with all the personality traits above.
– are you on the autism spectrum somewhere? one of simon baron-cohen’s systemizers or empathizers? do you have adhd? ocd? a touch of paranoid schizophrenia? (just because you’re paranoid….) all of these conditions can — and do! — obviously strongly affect the way individuals think and feel about the world around them.
– what’s your 2d:4d ratio? no one’s sure what’s behind the differences of these, but the ratio does correlate with all sorts of traits and behaviors.
– are you from what i call a “clannish” population or not? from a population that historically was located behind the hajnal line or not? you may disagree with me on why i think “clannishness” exists as a set of behavioral traits in different populations, but there’s not much disagreement on the fact that the behaviors do exist (and are measurable): individualism/collectivism vs. familism/non-collectivism; universalism vs. particularism; civic-minded/commonweal oriented vs. not civic-minded/not commonweal oriented; low corruption vs. high corruption; etc. again, you might be an exception to your population’s rule. then again, you may not be.
– do you think like a westerner?
– and, a special shout-out to one super-group: are you eastern european? if so, you might prefer authoritarianism (especially left-wing authoritarianism). keep in mind that others of us don’t.
that’s it! that’s all i’ve got for now. (^_^)
see also: me, myself, and i
(note: comments do not require an email. know thyself.)
this post is a companion piece to know thyself. you should read that post first. don’t have to, though! entirely up to you. (i score high on openness. (~_^) )
– i am female (although it’s hard to tell that from my writing style, apparently). i’m not a typical female, though. can’t stand romcoms (costume dramas are the exception), i’ve never read a romance novel (unless you count jane austen), hate gossip and gossiping, and my language skills are not very good. i do rather s*ck at math, though, so in that way i am typical female. and i like cute little fuzzy animals of all sorts! (^_^) did i mention that i knit?
(speaking of liking animals, i went missing on my grandparents’ farm when i was five. the adults couldn’t find me anywhere. eventually they discovered me sleeping in the field with the cows who were also sleeping. or chewing their cud or whatever they were doing. they were lying down anyway. (^_^) i still generally prefer the company of non-human animals. (~_^) present company excepted, of course!)
– i’m heterosexual.
– i’m so white i’m practically transparent. i’m some sort-of mix of irish and scottish — very much a creature of the british isles. so i come from a middling-“clannish” population that remained outside the hajnal line until very late. so you’d think i’d be clannish, and i do think that i express a few clannish traits (i probably possess more than i’d like to admit to).
one thing that i think is probably clannish about me is that i will very quickly, really without thinking, jump in to defend someone who i feel is part of my group. when i was a kid, these were school friends — the jocks could pick on me forever and a day, and i usually wouldn’t defend myself, but pick on one of my friends, and i’d turn into some sort of crazy banshee! even the teachers noted this as pretty odd, ’cause normally i was a real wallflower. (*^_^*) i think this clannish trait might account for some of my not-so-well-thought-out defenses here on the blog of individuals who have been watsoned. i jump into the fray to defend “one of my own” without much planning. like any trait, it has its pros and cons.
i’m distrustful of authority, which i think is possibly clannish. (although i’m not much of a lawbreaker. too square for that. is that the asperger’s? see below.) silly online quizzes keep telling me that i’m a libertarian, which again i think is possibly clannish. and i admit that my position against mass immigration could very well have something to do with my clannish nature (clannish people very often do not like The Other. i like other sorts of people/s, though. i do score high on openness — see below.). i used to not be against immigration of any sort, not until after i started reading about human biodiversity, so i really feel as though i’ve thought this issue through — it seems to make logical sense — but maybe it’s just my nature, and i’m fooling myself. i can admit to that possibility.
i think i might be less clannish than the average (native) irish, though, because one side of my family is originally from the lowlands of scotland. but maybe this is just wishful thinking on my part. (~_^)
– iq: 125? 130? not a genius, but not terribly dumb, either.
– personality traits? (see here and here.) i’m pretty to very open to experiences; low-ish on conscientiousness (have i not emailed you back yet? now you know why.); introverted, believe it or not (treat me gently!); low to average on agreeableness (does this account for my contrarian nature?); high on neuroticism/emotionality; high on honesty-humility. all in all, i’m a strange cookie!
my openness is probably my favorite of my personality traits. (or maybe the aspergeriness. close call.) i have always been open to new experiences and really curious about the world around me. and i LIKE being that way. (^_^) (and non-open people tend to bug me…which is not very open of me.) and i’ve been this way for as long as i can remember. kindergarten was soooo exciting because there was a mexican kid (i’d never met any mexicans before!) AND a kid who had chopped off one of his fingers! fascinating. again at age five i went missing (i must’ve gone missing a lot in those years!) when we were on a family vacation in the bahamas. they found me at the beach hanging out by the steel drum band. (~_^) and i remember being so very disappointed at age six or seven when the indian (native american) pow wow we were supposed to attend was rained out. (we were there, and we all had to leave! *sob*) i’ve always like The Different. (dad’s been to papua new guinea THREE times! WITHOUT ME!! hmpf. mom, too, will go anywhere, anytime. so there you go. runs in the family.)
my least favorite traits of mine are that i’m low on conscientiousness and high on neuroticism. just means that i worry all the time about all the things i haven’t gotten done yet. (>.<)
– i suspect i've got asperger's or am on the autistic spectrum somewhere. i certainly always score very high on all of simon baron-cohen’s “systemizing” (autism/asperger’s) tests. whatever the reason(s) for my high scores, whether i’m really an aspie or not, i think this part of my nature accounts for why i like reductionism so much. i like to tell myself that reductionism works — and in many cases it really does seem to! — but maybe it’s just ’cause i like it. (autists/aspies tend to like and be good at disciplines like engineering and the hard sciences, of course, being strong in “intuitive physics.”)
i also love science fiction (in case you hadn’t noticed), which is pretty aspergery. and i am socially awkward. or, rather, i have noooo idea what motivates people. (which i am sure partly drives my interest in hbd!)
i’m not sure, but i’m guessing some sort of combination of my aspergeriness (including the reductionism thing) plus openness plus my high scores on honesty i think, together, make me HATE political correctness. it’s just WRONG! oh, probably my contrarian nature, too. don’t like to follow the crowd. really don’t like to follow the crowd.
– how old am i? you never ask a woman her age! (~_^) (hint: i’m not a spring hbd chick.)
– i’m an agnostic. or some sort of athe-nostic. (i’m about as close as you could be to being an atheist while still being an agnostic. functionally, in everyday life, i’m an atheist.) been this way since i was fifteen. it just came to me like an epiphany one day. i don’t think i was even dwelling on the question at the time (i mean like that year or in those years). both of my parents are religious, and i went to catholic schools, but it didn’t stick. one of my grandfathers was an agnostic or atheist or something. i only found this out recently. nobody in the family wants to discuss it! hush-hush. (bad enough he was illegitimate! (~_^) )
– i’m not a full pessimist, but i do have pessimistic leanings. i was very much drawn toward the pessimists when i was younger (prolly still am, but i try to steer clear of them nowadays). couldn’t get enough of the existentialists when i was in my late teens (maybe that’s just all teens). true detective? i LOVED it! (except for the last ten minutes.) in other words, i’m a natural born conservative. (~_^) (dad’s always voted republican; mom, democrat. dad’s side of the family is the lowland scottish side; mom is soooo clannish, you would not believe!)
– i’m not a psychopath.
– my 2d:4d ratio is more like a guy’s than a chick’s: 96.9 (right hand). from what i’ve read, that’s pretty typical for female aspies. also, might be that inbred populations have lower average 2d:4d ratios. hmmmm. (also, and i’ve never seen this discussed wrt aspie chicks, i don’t have a very girly waist-to-hip ratio. i DO have a waist! i just never had an hourglass figure. even when i was at my thinnest. [98 pounds, if you must know. way back when!])
– according to only one short test (having only one question!), i don’t think like a westerner. that could be right. wouldn’t surprise me. (i still suspect that the “westerners” in these tests are western europeans from inside the hajnal line. could be wrong.)
– i am not eastern european and i DON’T like the idea of authoritarianism, left or right. not one. little. bit.
– my politics? i dunno. as i said, pew and cato keep telling me i’m a libertarian, but they’ve never asked me my thoughts on immigration. i’d say i’m some sort of fiscal+immigration conservative but socially a liberal (i don’t care if gays marry or not). the closest descriptor is prolly classical liberalism.
there’s more to me that i’m aware of, and presumably a lot more of which i am not, but this is all i’m going to share for now. a girl’s gotta have some secrets. (~_^)
ok. now you try! (just do this at home. not asking for any personal revelations in the comments!)
see also: know thyself
previously: my politics
(note: comments do not require an email. me, myself, and i.)