9 ms·

The Breeder's Equation

108 points by Bostonian 5y ago

wyager 5y ago
Wouldn't the 120 IQ subpopulation also have some people whose IQs are "genetically" more like 130 but they've gotten unlucky with environmental factors, pushing the genetic average a bit towards 120? It would be smaller than the number of 110 people who got lucky, but non-zero. Is this baked in to h^2?
sokoloff 5y ago
I’d expect if we find the kids of professors to be more likely to be National Merit Finalists that we’d find a non-zero upbringing/educational correlation. Sure there’s a genetic component, but I’d be fairly shocked if “being good on academic testing” has no correlation with “being raised by academics”.
- bordercases 5y ago
  And I'd be shocked if being a good academic had nothing to do with heritable traits.
- losvedir 5y ago
  Of course it would be correlated. Genes and environment and culture and family are all just one big interrelated mess. Is it even possible to tease the contributions apart, even in theory? I guess I could imagine a study, something like: look at kids of professors, in particular identical twins vs fraternal. Not all children will be National Merit Finalists, but among those that are, do you find identical twin pairs more often? Even that is subject to environmental effects, though, because potentially identical twins are raised differently!
  - bayesian_horse 5y ago
    I remember something about studies about "twins raised apart". In my opinion, Human nature is too complicate to poke at many of these factors, and talking about genetics quickly devolves into racism and elitism.
    - sokoloff 5y ago
      I agree with your last, which is very unfortunate in that if we could figure a way via research to shift upward the effectiveness of cognition (for which IQ is a proxy measure), I think peoples lives overall would be improved. Some of these are interventions that we’ve already found to prevent wasting of ability (as you cite in another comment); others might be nutritional or environmental changes we could make to better support development in utero or as children develop. Giving everyone 5% “better brains” would be a huge win for the world, but the sociological factors you mention preclude widespread scientific study.
      - LogonType10 5y ago
        You can't boost IQ, but you can stave off its decline with exercise. The reason why there's no incentive to do this is that no one wants smarter voters.
  - sokoloff 5y ago
    I agree with you but not the article which claims (without introducing evidence): “ By the way, when we say "environmental,” we mean “something other than additive genetics.” It doesn’t look as if the usual suspects—the way in which you raise your kids, or the school they attend—contribute much to this "environmental" variance, at least for adult IQ.” Perhaps studies of early adopted children would another pathway for study, but there seems to be little appetite for IQ study in general.
    - bayesian_horse 5y ago
      I remember, without having googled anything additionally, studies where Malaria infections and lead exposition had a negative effect on final IQ, whereas deworming treatments and longer school attendance had a positive effect.
- civilized 5y ago
  There are studies of twins raised separately that directly address this. We know a great deal about the genetic heritability of IQ, please have a look at this for more info: https://en.wikipedia.org/wiki/Heritability_of_IQ https://en.wikipedia.org/wiki/Heritability_of_IQ Extreme skepticism of social science findings is warranted for some subfields, but when it comes to intelligence, humanity has actually learned a lot.
baking 5y ago
Two people with IQ's of 120 will have kids with average IQ's of 110, but if you put those kids on an island and they have kids their average IQ's will be 110. What?
- AbrahamParangi 5y ago
  The original population has an avg IQ of 100 but the new island population has an avg IQ of 110
- jasongi 5y ago
  The parents genes are only 120 because 10 points were based on environmental "luck". Genetically they had the genes for 110 IQ +/- 10 points to accommodate the environmental luck. The two kids had average luck, so they got 110 IQ, but they still have the same genes. So when they have kids with others with the 110 IQ gene's, they will still be 110 +/- 10. A simpler explanation: you might be the child of geniuses but they dropped you on your head repeatedly as a baby. You might not be so smart as an adult because of it but your kids will have genius genes, not dropped on head genes.
  - deleted 5y ago
    [deleted]
- mattnewton 5y ago
  In the first example, their IQ of 120 is from a mix of factors and the author estimates some percentage that is due to the environment outside genetics, and that is what is lost in reverting to the mean of the environment. In the second example the author assumes that the environment of the desert island contributes nothing to genetics and so the offspring get the full 110 (heritability is 100%). It's odd to me though because it wasn't clear that the environment was meant to be affecting the parent and not the child too- the trick is the author treats the heritability parameter different for the parent and the child. Also, I don't think the desert island would actually have no effect on the 110 generation's IQ, or their upbringing outside of it, but I guess I can accept it as a thought-experiment-only place that does that by definition and not a literal desert island.
hirundo 5y ago
"And of course the breeder’s equation explains how average IQ potential is declining today, because of low fertility among highly educated women." In the Heinlein universe, the Howard Foundation runs a voluntary eugenics program by paying people with particularly long lived ancestors to mate with each other. Protagonist Lazarus Long is a product of this. The author is saying that this would work as expected, with offspring gaining around 50% of their parents' extra longevity. I'm a firm opponent of any kind of coercive eugenics. But it seems like it would be a good use of a billionaire's fortune to establish such a foundation for the promotion of intelligence, by paying very smart people to make babies together. But in Heinlein, the "Howards" became reviled and were forced off of the planet. If we do create a particularly smart population by eugenics, perhaps their primary task should be to find a way to protect themselves from us normals, a treatment for tall poppy syndrome. Of course, the first resort is secrecy. So we wouldn't know if they already exist.
- throwvirtever 5y ago
  An IQ is just a number coming out of a test. Whether or not that correlates to something useful for humanity, or even the individual being tested, is a different question. Surely the majority of useful discoveries are made by people with above-average IQs, but would juicing the numbers through eugenics really make much of a difference? How many extra Isaac Newtons would it take to make controlled nuclear fusion work? Because if we don't have an estimate for that, why would we expect an intelligence-focused eugenics program to be useful at all?
  - notahacker 5y ago
    Not to mention the regression to the mean issue discussed in the article, and the slight problem of attracting women aware that they have a very high IQ to trade career success or other personal preferences for being the baby making machine for some billionaire's experiment. It's not like they're currently disproportionately likely to choose not to have kids because they can't afford them
    - PKop 5y ago
paulcnichols 5y ago
Spicy topic!
max_ 5y ago
"And of course the breeder’s equation explains how average IQ potential is declining today, because of low fertility among highly educated women." Do highly educated women have a high IQ? Or does a high IQ make you a highly educated woman? The writer seems to start with the conclusion that highly educated women generally have high IQs.
- fyhgdet 5y ago
  The writer starts with that unstated assumption. It’s not the conclusion.
- pjscott 5y ago
  It's been found empirically that IQ and educational attainment are moderately correlated.
Causality1 5y ago
Like most looming disasters, whether or not this is a real problem depends on quantifying the problem. Is this likely to significantly affect the population intelligence before we learn to engineer our children, say within the next 200 years?
- bagels 5y ago
  I always find these statements interesting. Do you think many people 200 years ago based their actions on what effect they would have on those people 200 years hence?
  - Causality1 5y ago
    Oh I'm not saying we will. I'm just saying that even taking the claimed effect at face value, it only has significance if it can hurt our genetic intelligence faster than engineering can improve it.
abeppu 5y ago
From a didactic perspective, I think he goes off the rails by immediately focusing on something as abstract and hard to measure as intelligence, and where there's a long history of people talking about whether it's even a single trait. In terms of just explaining the breeder's equation, I think he could have been more effective talking about, IDK, tall Dutch people. The other thing that's annoying here is that although this is an 'equation', as I understand it it's typically not predictive because that heritability term is so fuzzy. It's not that you know the heritability term in advance and predict the response to selection; measuring the response to selection also updates your information about the heritability. His examples have a cherry-picking feel for this reason. Take the "national merit finalists" thing he mentions multiple times. Note that he doesn't mention the IQ distribution of the college professors (surely it's logistically impractical to get any large number of busy faculty to spend time taking such tests) or of the college towns (which might not be the same as the overall population mean), or the degree to which being a professor is correlated with IQ or the degree to which being a national merit finalists is correlated to IQ. Had the data come out differently (and I suspect he mentions _finalist_ multiple times because there wasn't as distinct a signal among _winners_), this perspective leaves plenty of room to declare that (a) maybe heritability of intelligence is lower than initially thought or assortative mating along IQ lines is weaker than expected (b) maybe professor-ness is less correlated to IQ than assumed or (c) maybe national merit finalist status isn't especially correlated to IQ (semifinalists have to submit a bunch of info other than test results).
- mynameishere 5y ago
  This kind of quibbling always comes up. He's just using professors and national merit finalists as examples. The truth is, you could probably take the top 10 percent highest-earning car salesmen (EDIT: and women), drop them on a desert island and, after two generations, get the highest-IQ society the world has ever known. But that's less obvious, so why use such an example?
  - ImaCake 5y ago
    But it’s not clear at all that intelligence is a single trait. It is incredibly messy and this means any analysis of it has to be very careful of confounders. In contrast, height is by many definitions a single trait, we know exactly what confounds it’s measurement (and those things are easy to measure!) and we have a pretty good estimate of it’s heritability.
bayesian_horse 5y ago
The heritability of intelligence is overhyped, and in my opinion of no practical use. It's extremely hard to find data where it is even possible to distinguish between genetic and environmental influence. That would be the studies of the kind "twins raised apart". And that already excludes the reality that those twins will probably grow up in a similar background, similar health and educational system etc. The talk about heritable IQ is pointless, even dangerous, because it leads to complacency around issues around structural racism and equality in education.
- pjscott 5y ago
  The usual studies for disentangling genetics and environment involve twins raised together: they get basically the same shared environment -- this is a feature, not a bug -- but identical twins are more closely related than fraternal twins. For example, say you're trying to find out how much of adult height comes down to genetics (in a modern, non-malnourished environment). You measure the heights of a bunch of twins and compare: how much more similar are the heights of identical twins than the heights of fraternal twins? Do a bit of calculating and you've got a number for heritability.
  - bayesian_horse 5y ago
    Yes. But then people take that street number from a "twins raised together" study and quote it as heritability of intelligence overall. My problem with this: Yes, if you put extreme limits on the environmental factors, you are mostly left with genetic factors. But that is not the reality of Human existence.
- daenz 5y ago
  >The talk about heritable IQ is pointless, even dangerous, because it leads to complacency around issues around structural racism and equality in education. Can you say more about this? Why would it lead to complacency? If there is scientific merit to some ideas like IQ heritability, don't you think we need to find a way to incorporate those ideas safely into our formulation of society, rather than suppress them as heretical?
nfmcclure 5y ago
I'm very happy to see "The Breeder's Equation" on Hacker News. Wow. I spent my graduate career studying mathematical biology and working with biologists. It's a fascinating equation and I spent some time on it converting it from a discrete equation into a continuous equation along with explaining the use cases and motivations behind it here: http://fromdata.org/2013/10/27/the-continuous-breeders-equation/ http://fromdata.org/2013/10/27/the-continuous-breeders-equat... This of course, does not take into account mutation, transduction, conjugation and other sources of genetic variation. Edit: Please take these approximate expectation equations with a grain of salt. They only apply to larger, discrete-reproducing, controlled populations. Applying results like these on spatially segregated or small populations does not really work. Also this equation does break down a bit when the phenotypic trait is a result of very complicated interactions between genetics and the environment.
s28l 5y ago
The author is playing fast and loose with definitions here. Other sources[0][1] (that I would consider more reputable) define the breeder's equation in terms of populations, but this author focuses on arbitrary and ill-defined subsets of populations. Crucially, the author defines R as "the response to selection", but he omits the second part: "from one generation to the next". Source [0] defines it even more clearly: "the change in the mean [of the population] over one complete generation". Similarly, S is the difference in the measured trait among the entire population and the population that reproduces. So when the author considers "a set of parents with IQs of 120", it only fits the correct usage of the equation if we take that to mean that mean IQ of all parents in this generation is 120. If that's his argument, how is he defining the population of parents? In my opinion, this is a wishy-washy argument that seems like a subtle way of advancing eugenics (or something similarly distasteful). [0]: https://www.nature.com/scitable/knowledge/library/the-breeder-s-equation-24204828/ https://www.nature.com/scitable/knowledge/library/the-breede... [1]: https://public.wsu.edu/~gomulki/biol519/presentations/SjobergStraussLarkinPSS.pdf https://public.wsu.edu/~gomulki/biol519/presentations/Sjober...
- civilized 5y ago
  I'd like to understand what this comment is saying, but I can't follow. Could someone please explain more clearly what exact intellectual mistake the author allegedly made? The exposition in the OP seems very simple and clear, and I cannot seem to relate the definitional issues raised here to what is said in the article. In the article's first thought experiment, we take a population with IQ 100, pull out the subset with IQ 120, have that IQ 120 subset breed with one another. According to the breeder's equation, we get children with average IQ 110. What is "arbitrary", "ill-defined", "fast and loose", etc. about this? It seems to be a standard application of the equation, no different than how one might breed cows for milk or tomatoes for size. It's quite unclear how the "crucial" clause "from one generation to the next" undermines any of this. And could we perhaps focus on understanding what was said before muddying the waters with unsubstantiated accusations of eugenics? HN rules say that HN is for learning and understanding, not ideological warfare.
  - s28l 5y ago
Gregaros 5y ago
> It also explains why the professors’ kids are a disproportionate fraction of the National Merit Finalists in a college town. […] But those kids, although smarter than average, usually aren’t as smart as their *fathers*: partly because their *mothers* typically aren’t theoretical physicists, partly because of regression towards the mean. Wow, this guy is … not concerned with political correctness/not considering whether or not the college professors worth mentioning are guaranteed to be male.
- rkk3 5y ago
  Ironic since their department, Anthropology, is one of the most politically-correct and female academic disciplines.
  - LogonType10 5y ago
    Maybe they don't think anthropologists have high IQ.
- jyscao 5y ago
  Well, the context of your quoted statement was provided in the paragraph above: > Reminds me of the fact that Los Alamos High School has the highest test scores in New Mexico. He's referring specifically to the physicists working on the Manhattan project, who were definitely predominantly male.
  - Gregaros 5y ago
    That’s not right, either, since he is speaking in the present tense and comparing his current local high school’s attempts to emulate what Los Alamos high currently does: > Reminds me of the fact that Los Alamos High School has the highest test scores in New Mexico. Our local high school tried copying their schedule, in search of the secret. Didn’t work. I know of an approach that would, but it takes about fifteen years.
    - jyscao 5y ago
gumby 5y ago
> Eugenics is not only possible, it’s trivial. If you select for a single, measurable trait, perhaps. We do this all the time, with limited success, in breeding lab test animals, dog breeds and such. But for survivability eugenics is hard: there are multiple dice rolls each cycle, not just the chromosomal mixing, but environment too, and that adds not just epigemetic change but different environments for which various traits might be temporarily valuable. You can see this demonstrated by the inbreeding of the royal houses of Europe. They have recognized this too as they have been widening their gene pool for decades. Even the magic island experiment described from which I extracted that sentence would suffer under that too. Selective pressure is hard.
- ImaCake 5y ago
  > multiple dice rolls each cycle This is an understatement, just considering SNPs, there is at least several hundred thousand statistically independent coin flips when two parents breed. It is difficult to overstate how powerful an evolutionary tool this is, and the implications it has for breeding.
ImaCake 5y ago
This is a pretty poor quality article. I say this as someone who works in a population genetics research group. If you like some actually thoughtful reading on genetics and eugenics I would point you towards gwern who, as far as I can tell, seems to at least get the science and math right. https://www.gwern.net/tags/genetics https://www.gwern.net/tags/genetics
- civilized 5y ago
  Could we trouble you for a little detail about what's wrong with the article? It seems very clear and understandable for the layman, so it would be good to have an equally clear explanation of what's wrong with it.

108 points by Bostonian 5y ago

Wouldn't the 120 IQ subpopulation also have some people whose IQs are "genetically" more like 130 but they've gotten unlucky with environmental factors, pushing the genetic average a bit towards 120? It would be smaller than the number of 110 people who got lucky, but non-zero. Is this baked in to h^2?

sokoloff 5y ago

I’d expect if we find the kids of professors to be more likely to be National Merit Finalists that we’d find a non-zero upbringing/educational correlation. Sure there’s a genetic component, but I’d be fairly shocked if “being good on academic testing” has no correlation with “being raised by academics”.

bordercases 5y ago
And I'd be shocked if being a good academic had nothing to do with heritable traits.
losvedir 5y ago
Of course it would be correlated. Genes and environment and culture and family are all just one big interrelated mess. Is it even possible to tease the contributions apart, even in theory? I guess I could imagine a study, something like: look at kids of professors, in particular identical twins vs fraternal. Not all children will be National Merit Finalists, but among those that are, do you find identical twin pairs more often? Even that is subject to environmental effects, though, because potentially identical twins are raised differently!
- bayesian_horse 5y ago
  I remember something about studies about "twins raised apart". In my opinion, Human nature is too complicate to poke at many of these factors, and talking about genetics quickly devolves into racism and elitism.
  - sokoloff 5y ago
    I agree with your last, which is very unfortunate in that if we could figure a way via research to shift upward the effectiveness of cognition (for which IQ is a proxy measure), I think peoples lives overall would be improved. Some of these are interventions that we’ve already found to prevent wasting of ability (as you cite in another comment); others might be nutritional or environmental changes we could make to better support development in utero or as children develop. Giving everyone 5% “better brains” would be a huge win for the world, but the sociological factors you mention preclude widespread scientific study.
    - LogonType10 5y ago
      You can't boost IQ, but you can stave off its decline with exercise. The reason why there's no incentive to do this is that no one wants smarter voters.
- sokoloff 5y ago
  I agree with you but not the article which claims (without introducing evidence): “ By the way, when we say "environmental,” we mean “something other than additive genetics.” It doesn’t look as if the usual suspects—the way in which you raise your kids, or the school they attend—contribute much to this "environmental" variance, at least for adult IQ.” Perhaps studies of early adopted children would another pathway for study, but there seems to be little appetite for IQ study in general.
  - bayesian_horse 5y ago
    I remember, without having googled anything additionally, studies where Malaria infections and lead exposition had a negative effect on final IQ, whereas deworming treatments and longer school attendance had a positive effect.
civilized 5y ago
There are studies of twins raised separately that directly address this. We know a great deal about the genetic heritability of IQ, please have a look at this for more info: https://en.wikipedia.org/wiki/Heritability_of_IQ https://en.wikipedia.org/wiki/Heritability_of_IQ Extreme skepticism of social science findings is warranted for some subfields, but when it comes to intelligence, humanity has actually learned a lot.

baking 5y ago

Two people with IQ's of 120 will have kids with average IQ's of 110, but if you put those kids on an island and they have kids their average IQ's will be 110. What?

AbrahamParangi 5y ago
The original population has an avg IQ of 100 but the new island population has an avg IQ of 110
jasongi 5y ago
The parents genes are only 120 because 10 points were based on environmental "luck". Genetically they had the genes for 110 IQ +/- 10 points to accommodate the environmental luck. The two kids had average luck, so they got 110 IQ, but they still have the same genes. So when they have kids with others with the 110 IQ gene's, they will still be 110 +/- 10. A simpler explanation: you might be the child of geniuses but they dropped you on your head repeatedly as a baby. You might not be so smart as an adult because of it but your kids will have genius genes, not dropped on head genes.
- deleted 5y ago
  [deleted]
mattnewton 5y ago
In the first example, their IQ of 120 is from a mix of factors and the author estimates some percentage that is due to the environment outside genetics, and that is what is lost in reverting to the mean of the environment. In the second example the author assumes that the environment of the desert island contributes nothing to genetics and so the offspring get the full 110 (heritability is 100%). It's odd to me though because it wasn't clear that the environment was meant to be affecting the parent and not the child too- the trick is the author treats the heritability parameter different for the parent and the child. Also, I don't think the desert island would actually have no effect on the 110 generation's IQ, or their upbringing outside of it, but I guess I can accept it as a thought-experiment-only place that does that by definition and not a literal desert island.

hirundo 5y ago

"And of course the breeder’s equation explains how average IQ potential is declining today, because of low fertility among highly educated women." In the Heinlein universe, the Howard Foundation runs a voluntary eugenics program by paying people with particularly long lived ancestors to mate with each other. Protagonist Lazarus Long is a product of this. The author is saying that this would work as expected, with offspring gaining around 50% of their parents' extra longevity. I'm a firm opponent of any kind of coercive eugenics. But it seems like it would be a good use of a billionaire's fortune to establish such a foundation for the promotion of intelligence, by paying very smart people to make babies together. But in Heinlein, the "Howards" became reviled and were forced off of the planet. If we do create a particularly smart population by eugenics, perhaps their primary task should be to find a way to protect themselves from us normals, a treatment for tall poppy syndrome. Of course, the first resort is secrecy. So we wouldn't know if they already exist.

throwvirtever 5y ago
An IQ is just a number coming out of a test. Whether or not that correlates to something useful for humanity, or even the individual being tested, is a different question. Surely the majority of useful discoveries are made by people with above-average IQs, but would juicing the numbers through eugenics really make much of a difference? How many extra Isaac Newtons would it take to make controlled nuclear fusion work? Because if we don't have an estimate for that, why would we expect an intelligence-focused eugenics program to be useful at all?
- notahacker 5y ago
  Not to mention the regression to the mean issue discussed in the article, and the slight problem of attracting women aware that they have a very high IQ to trade career success or other personal preferences for being the baby making machine for some billionaire's experiment. It's not like they're currently disproportionately likely to choose not to have kids because they can't afford them
  - PKop 5y ago

paulcnichols 5y ago

Spicy topic!

max_ 5y ago

"And of course the breeder’s equation explains how average IQ potential is declining today, because of low fertility among highly educated women." Do highly educated women have a high IQ? Or does a high IQ make you a highly educated woman? The writer seems to start with the conclusion that highly educated women generally have high IQs.

fyhgdet 5y ago
The writer starts with that unstated assumption. It’s not the conclusion.
pjscott 5y ago
It's been found empirically that IQ and educational attainment are moderately correlated.

Causality1 5y ago

Like most looming disasters, whether or not this is a real problem depends on quantifying the problem. Is this likely to significantly affect the population intelligence before we learn to engineer our children, say within the next 200 years?

bagels 5y ago
I always find these statements interesting. Do you think many people 200 years ago based their actions on what effect they would have on those people 200 years hence?
- Causality1 5y ago
  Oh I'm not saying we will. I'm just saying that even taking the claimed effect at face value, it only has significance if it can hurt our genetic intelligence faster than engineering can improve it.

abeppu 5y ago

From a didactic perspective, I think he goes off the rails by immediately focusing on something as abstract and hard to measure as intelligence, and where there's a long history of people talking about whether it's even a single trait. In terms of just explaining the breeder's equation, I think he could have been more effective talking about, IDK, tall Dutch people. The other thing that's annoying here is that although this is an 'equation', as I understand it it's typically not predictive because that heritability term is so fuzzy. It's not that you know the heritability term in advance and predict the response to selection; measuring the response to selection also updates your information about the heritability. His examples have a cherry-picking feel for this reason. Take the "national merit finalists" thing he mentions multiple times. Note that he doesn't mention the IQ distribution of the college professors (surely it's logistically impractical to get any large number of busy faculty to spend time taking such tests) or of the college towns (which might not be the same as the overall population mean), or the degree to which being a professor is correlated with IQ or the degree to which being a national merit finalists is correlated to IQ. Had the data come out differently (and I suspect he mentions _finalist_ multiple times because there wasn't as distinct a signal among _winners_), this perspective leaves plenty of room to declare that (a) maybe heritability of intelligence is lower than initially thought or assortative mating along IQ lines is weaker than expected (b) maybe professor-ness is less correlated to IQ than assumed or (c) maybe national merit finalist status isn't especially correlated to IQ (semifinalists have to submit a bunch of info other than test results).

mynameishere 5y ago
This kind of quibbling always comes up. He's just using professors and national merit finalists as examples. The truth is, you could probably take the top 10 percent highest-earning car salesmen (EDIT: and women), drop them on a desert island and, after two generations, get the highest-IQ society the world has ever known. But that's less obvious, so why use such an example?
- ImaCake 5y ago
  But it’s not clear at all that intelligence is a single trait. It is incredibly messy and this means any analysis of it has to be very careful of confounders. In contrast, height is by many definitions a single trait, we know exactly what confounds it’s measurement (and those things are easy to measure!) and we have a pretty good estimate of it’s heritability.

bayesian_horse 5y ago

The heritability of intelligence is overhyped, and in my opinion of no practical use. It's extremely hard to find data where it is even possible to distinguish between genetic and environmental influence. That would be the studies of the kind "twins raised apart". And that already excludes the reality that those twins will probably grow up in a similar background, similar health and educational system etc. The talk about heritable IQ is pointless, even dangerous, because it leads to complacency around issues around structural racism and equality in education.

pjscott 5y ago
The usual studies for disentangling genetics and environment involve twins raised together: they get basically the same shared environment -- this is a feature, not a bug -- but identical twins are more closely related than fraternal twins. For example, say you're trying to find out how much of adult height comes down to genetics (in a modern, non-malnourished environment). You measure the heights of a bunch of twins and compare: how much more similar are the heights of identical twins than the heights of fraternal twins? Do a bit of calculating and you've got a number for heritability.
- bayesian_horse 5y ago
  Yes. But then people take that street number from a "twins raised together" study and quote it as heritability of intelligence overall. My problem with this: Yes, if you put extreme limits on the environmental factors, you are mostly left with genetic factors. But that is not the reality of Human existence.
daenz 5y ago
>The talk about heritable IQ is pointless, even dangerous, because it leads to complacency around issues around structural racism and equality in education. Can you say more about this? Why would it lead to complacency? If there is scientific merit to some ideas like IQ heritability, don't you think we need to find a way to incorporate those ideas safely into our formulation of society, rather than suppress them as heretical?

nfmcclure 5y ago

I'm very happy to see "The Breeder's Equation" on Hacker News. Wow. I spent my graduate career studying mathematical biology and working with biologists. It's a fascinating equation and I spent some time on it converting it from a discrete equation into a continuous equation along with explaining the use cases and motivations behind it here: http://fromdata.org/2013/10/27/the-continuous-breeders-equation/ http://fromdata.org/2013/10/27/the-continuous-breeders-equat... This of course, does not take into account mutation, transduction, conjugation and other sources of genetic variation. Edit: Please take these approximate expectation equations with a grain of salt. They only apply to larger, discrete-reproducing, controlled populations. Applying results like these on spatially segregated or small populations does not really work. Also this equation does break down a bit when the phenotypic trait is a result of very complicated interactions between genetics and the environment.

s28l 5y ago

The author is playing fast and loose with definitions here. Other sources[0][1] (that I would consider more reputable) define the breeder's equation in terms of populations, but this author focuses on arbitrary and ill-defined subsets of populations. Crucially, the author defines R as "the response to selection", but he omits the second part: "from one generation to the next". Source [0] defines it even more clearly: "the change in the mean [of the population] over one complete generation". Similarly, S is the difference in the measured trait among the entire population and the population that reproduces. So when the author considers "a set of parents with IQs of 120", it only fits the correct usage of the equation if we take that to mean that mean IQ of all parents in this generation is 120. If that's his argument, how is he defining the population of parents? In my opinion, this is a wishy-washy argument that seems like a subtle way of advancing eugenics (or something similarly distasteful). [0]: https://www.nature.com/scitable/knowledge/library/the-breeder-s-equation-24204828/ https://www.nature.com/scitable/knowledge/library/the-breede... [1]: https://public.wsu.edu/~gomulki/biol519/presentations/SjobergStraussLarkinPSS.pdf https://public.wsu.edu/~gomulki/biol519/presentations/Sjober...

civilized 5y ago
I'd like to understand what this comment is saying, but I can't follow. Could someone please explain more clearly what exact intellectual mistake the author allegedly made? The exposition in the OP seems very simple and clear, and I cannot seem to relate the definitional issues raised here to what is said in the article. In the article's first thought experiment, we take a population with IQ 100, pull out the subset with IQ 120, have that IQ 120 subset breed with one another. According to the breeder's equation, we get children with average IQ 110. What is "arbitrary", "ill-defined", "fast and loose", etc. about this? It seems to be a standard application of the equation, no different than how one might breed cows for milk or tomatoes for size. It's quite unclear how the "crucial" clause "from one generation to the next" undermines any of this. And could we perhaps focus on understanding what was said before muddying the waters with unsubstantiated accusations of eugenics? HN rules say that HN is for learning and understanding, not ideological warfare.
- s28l 5y ago

Gregaros 5y ago

> It also explains why the professors’ kids are a disproportionate fraction of the National Merit Finalists in a college town. […] But those kids, although smarter than average, usually aren’t as smart as their *fathers*: partly because their *mothers* typically aren’t theoretical physicists, partly because of regression towards the mean. Wow, this guy is … not concerned with political correctness/not considering whether or not the college professors worth mentioning are guaranteed to be male.

rkk3 5y ago
Ironic since their department, Anthropology, is one of the most politically-correct and female academic disciplines.
- LogonType10 5y ago
  Maybe they don't think anthropologists have high IQ.
jyscao 5y ago
Well, the context of your quoted statement was provided in the paragraph above: > Reminds me of the fact that Los Alamos High School has the highest test scores in New Mexico. He's referring specifically to the physicists working on the Manhattan project, who were definitely predominantly male.
- Gregaros 5y ago
  That’s not right, either, since he is speaking in the present tense and comparing his current local high school’s attempts to emulate what Los Alamos high currently does: > Reminds me of the fact that Los Alamos High School has the highest test scores in New Mexico. Our local high school tried copying their schedule, in search of the secret. Didn’t work. I know of an approach that would, but it takes about fifteen years.
  - jyscao 5y ago

gumby 5y ago

> Eugenics is not only possible, it’s trivial. If you select for a single, measurable trait, perhaps. We do this all the time, with limited success, in breeding lab test animals, dog breeds and such. But for survivability eugenics is hard: there are multiple dice rolls each cycle, not just the chromosomal mixing, but environment too, and that adds not just epigemetic change but different environments for which various traits might be temporarily valuable. You can see this demonstrated by the inbreeding of the royal houses of Europe. They have recognized this too as they have been widening their gene pool for decades. Even the magic island experiment described from which I extracted that sentence would suffer under that too. Selective pressure is hard.

ImaCake 5y ago
> multiple dice rolls each cycle This is an understatement, just considering SNPs, there is at least several hundred thousand statistically independent coin flips when two parents breed. It is difficult to overstate how powerful an evolutionary tool this is, and the implications it has for breeding.

ImaCake 5y ago

This is a pretty poor quality article. I say this as someone who works in a population genetics research group. If you like some actually thoughtful reading on genetics and eugenics I would point you towards gwern who, as far as I can tell, seems to at least get the science and math right. https://www.gwern.net/tags/genetics https://www.gwern.net/tags/genetics

civilized 5y ago
Could we trouble you for a little detail about what's wrong with the article? It seems very clear and understandable for the layman, so it would be good to have an equally clear explanation of what's wrong with it.