> ...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.
It's one of the main drivers of varying housing costs in the US.
> We have 3 sources of difference, genetic heritability, home environment and "others"
Clearly, school is not home environment.
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.
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/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."
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?
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.
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.