4 ms·

I think it's worth pointing out that "heritability" means something very unintuitive in the literature. It measure the fraction of the variability that can be a

I think it's worth pointing out that "heritability" means something very unintuitive in the literature. It measure the fraction of the variability that can be attributed to genetic variation, as opposed to environmental factors. This does not mean what people think it means. In particular, the changes in environment can drastically affect the heritability of a trait. An example: suppose you measure how fast people can run. If you take people and forbid them from training (say, lock them in a room), the variability will be fully heritable, since no one is training and the environment is exactly the same. The difference will be whatever the genes say it is. Conversely, if you make some of them train and other not, the variability will include environmental components, namely, who trains. This has obvious implications for how to interpret this and similar results, depending on whether you find high heritability a good thing or a bad thing.

username90 7y ago
No, the studies are very clear, we take the variance of nature and variance of nurture at a population level and see how much a standard deviation effects some observable trait. Of course if you look at extreme cases of nature or nurture like being locked up your entire life or being born with a birth defect then that part will dominate, but we can still look at the overall population distribution and say something relevant about heritability since most people have pretty normal genes and environments.
- lucienlecam 7y ago
  Heritability (i.e. narrow-sense heritability as typically used in most research articles) is not so clear-cut as to be split between nature and nurture. Even the GP is slightly incorrect when saying: > ...as opposed to environmental factors because for heritability, the distinction is between the variance explained by additive genetic effects versus the total variance of the trait of interest. There are other sources of phenotypic variance like epigenetics, non-additive genetic effects, or complex interactions that fall outside the scope of heritability.
  - username90 7y ago
    We have 3 sources of difference, genetic heritability, home environment and "others". The things you talk about would go under "others", and they aren't very interesting since we have basically no influence over them, as everything we can influence via nurture goes under home environment and nature via genetic heritage. So for example, of we compare growing up in a rich or a poor household (this includes going to a better school, better neighborhood, better food etc), most of these studies shows that it has almost no effect at all.
    - BurningFrog 7y ago
      You influence "others" by putting your kids in a good school. It's one of the main drivers of varying housing costs in the US.
      - deleted 7y ago
        [deleted]
      - username90 7y ago
        Your parents determines your school, so the quality of your school can't be in "others". The only way school could be in "others" in these studies is if parents often put one twin in a good school and the other twin in a bad school, but I strongly believe that isn't the case.
        BurningFrog 7y ago
        In your own words: > We have 3 sources of difference, genetic heritability, home environment and "others" Clearly, school is not home environment.
        username90 7y ago
        School is determines by your home environment, hence it is a part of the home environment bucket. "other" is not: "everything except home environment and genes", it is: "everything not determined by the home environment or genes".
- abathur 7y ago
  I don't think this negates the parent's concern. The parent uses an extreme example, but I think the underlying concern is: what assumptions get baked in when we assume the available environments are pretty normal? Our modern environments are very abnormal compared to human environments for most of human genetic history. We can measure traits of statistically "normal" humans living in statistically "normal" environments and still ultimately be sampling in a weird corner of the possibility space.
  - username90 7y ago
    Normal as in there is very little difference between the lives of most people in first world nations. They go to a school for a decade and don't have to worry about sleeping out in the rain or going hungry. That is enough for kids to bloom. If you deny them any of those then there are problems, but that is not an issue even for poor people in the west.
    - Enginerrrd 7y ago
      >They go to a school for a decade and don't have to worry about sleeping out in the rain or going hungry. [...] but that is not an issue even for poor people in the west. Ooof. Just FYI this is actually horribly out of touch with reality. Go talk to a social worker sometime, or someone that runs a soup kitchen/shelter. Or just check out the official government stats for the US: https://www.ers.usda.gov/topics/food-nutrition-assistance/food-security-in-the-us/key-statistics-graphics.aspx#children https://www.ers.usda.gov/topics/food-nutrition-assistance/fo... To quote: "Both children and adults were food insecure in 7.1 percent of households with children (2.7 million households. Although children are usually protected from substantial reductions in food intake even in households with very low food security, nevertheless, in about 0.6 percent of households with children (220,000 households), one or more child also experienced reduced food intake and disrupted eating patterns at some time during the year."
- majormajor 7y ago
  > we can still look at the overall population distribution and say something relevant about heritability since most people have pretty normal genes and environments So if you had some groups with generally fairly different genes and environments both, this would ascribe any differences just to the genes and throw out the environment aspect?
chongli 7y ago
Conversely, if you make some of them train and other not, the variability will include environmental components, namely, who trains. But then if you take everyone and train them to the max, i.e. Olympic athletes, then heritability comes back into the picture in a big way.
- shard972 7y ago
  nazi!
- afthonos 7y ago
  Indeed. I posted because I think intuitively people read that a trait is 60% heritable and assume that it's always true, when it is only true in the specific environment in which it was measured.

username90 7y ago

No, the studies are very clear, we take the variance of nature and variance of nurture at a population level and see how much a standard deviation effects some observable trait. Of course if you look at extreme cases of nature or nurture like being locked up your entire life or being born with a birth defect then that part will dominate, but we can still look at the overall population distribution and say something relevant about heritability since most people have pretty normal genes and environments.

lucienlecam 7y ago
Heritability (i.e. narrow-sense heritability as typically used in most research articles) is not so clear-cut as to be split between nature and nurture. Even the GP is slightly incorrect when saying: > ...as opposed to environmental factors because for heritability, the distinction is between the variance explained by additive genetic effects versus the total variance of the trait of interest. There are other sources of phenotypic variance like epigenetics, non-additive genetic effects, or complex interactions that fall outside the scope of heritability.
- username90 7y ago
  We have 3 sources of difference, genetic heritability, home environment and "others". The things you talk about would go under "others", and they aren't very interesting since we have basically no influence over them, as everything we can influence via nurture goes under home environment and nature via genetic heritage. So for example, of we compare growing up in a rich or a poor household (this includes going to a better school, better neighborhood, better food etc), most of these studies shows that it has almost no effect at all.
  - BurningFrog 7y ago
    You influence "others" by putting your kids in a good school. It's one of the main drivers of varying housing costs in the US.
    - deleted 7y ago
      [deleted]
    - username90 7y ago
      Your parents determines your school, so the quality of your school can't be in "others". The only way school could be in "others" in these studies is if parents often put one twin in a good school and the other twin in a bad school, but I strongly believe that isn't the case.
      - BurningFrog 7y ago
        In your own words: > We have 3 sources of difference, genetic heritability, home environment and "others" Clearly, school is not home environment.
        username90 7y ago
        School is determines by your home environment, hence it is a part of the home environment bucket. "other" is not: "everything except home environment and genes", it is: "everything not determined by the home environment or genes".
abathur 7y ago
I don't think this negates the parent's concern. The parent uses an extreme example, but I think the underlying concern is: what assumptions get baked in when we assume the available environments are pretty normal? Our modern environments are very abnormal compared to human environments for most of human genetic history. We can measure traits of statistically "normal" humans living in statistically "normal" environments and still ultimately be sampling in a weird corner of the possibility space.
- username90 7y ago
  Normal as in there is very little difference between the lives of most people in first world nations. They go to a school for a decade and don't have to worry about sleeping out in the rain or going hungry. That is enough for kids to bloom. If you deny them any of those then there are problems, but that is not an issue even for poor people in the west.
  - Enginerrrd 7y ago
    >They go to a school for a decade and don't have to worry about sleeping out in the rain or going hungry. [...] but that is not an issue even for poor people in the west. Ooof. Just FYI this is actually horribly out of touch with reality. Go talk to a social worker sometime, or someone that runs a soup kitchen/shelter. Or just check out the official government stats for the US: https://www.ers.usda.gov/topics/food-nutrition-assistance/food-security-in-the-us/key-statistics-graphics.aspx#children https://www.ers.usda.gov/topics/food-nutrition-assistance/fo... To quote: "Both children and adults were food insecure in 7.1 percent of households with children (2.7 million households. Although children are usually protected from substantial reductions in food intake even in households with very low food security, nevertheless, in about 0.6 percent of households with children (220,000 households), one or more child also experienced reduced food intake and disrupted eating patterns at some time during the year."
majormajor 7y ago
> we can still look at the overall population distribution and say something relevant about heritability since most people have pretty normal genes and environments So if you had some groups with generally fairly different genes and environments both, this would ascribe any differences just to the genes and throw out the environment aspect?

chongli 7y ago

Conversely, if you make some of them train and other not, the variability will include environmental components, namely, who trains. But then if you take everyone and train them to the max, i.e. Olympic athletes, then heritability comes back into the picture in a big way.

shard972 7y ago
nazi!
afthonos 7y ago
Indeed. I posted because I think intuitively people read that a trait is 60% heritable and assume that it's always true, when it is only true in the specific environment in which it was measured.