If race were a factor in twin studies, I think it would show up only in shared environment, since it differs between families but never within families (and is not differently different in MZ vs. DZ twins). That means it would not show in “heredity”, unless we’re talking about interracial couples with two children, each of whom by coincidence got a very different number of genes from the parents’ two races—I think this is rare enough not to matter in real life studies.
Your point stands about the general role of these kinds of things, I just don’t think it’s counted that way in the twin studies we actually have.
You’re right about beauty etc, though. Genetic studies are most informative about interventions to change individuals’ standings relative to other individuals, not about interventions to completely change the nature of the playing field.
But I think it would, unless I’m misunderstanding. If the world is (uniformly) biased against blacks, then the genes for “blackness” would be correlated with reduced outcomes, with no environmental effects since all environments are equally prejudiced.
For the effect to show up in environment, you’d have to have varying environments with different levels of prejudice; if the differences are pronounced enough, then you’d start seeing racial variations on the environmental side.
In a world where it was indeed perfectly even, lets say a world with a highly regimented system of prejudice where everyone’s skin tone is carefully measured and restrictions were then applied across the country.
But if prejudice isn’t perfectly even or measuring the same things then you’d expect it to vary. If one twin grows up in a town where most of the residents still oppose miscegenation while the other ends up in a town with far less prejudice then the difference is going to show up as environmental.
Or if they have the same accent and same skin tone but one grows up in a town where people are more prejudiced about cultural markers like accent and dress while the other grows up in a town where they care more about biological markers the difference would show up as environmental.
Also it’s common to run PCA when dealing with samples from different ethnic origins to make it easy to spot when you’ve simply flagged up a variant linked to one group.
If your flagged variant overlaps almost totally with only one group then it can be a sign that your analysis has been confounded though overlapping a little more with one group than with others is to be expected.
But if prejudice isn’t perfectly even or measuring the same things then you’d expect it to vary.
Yep. And depending on both the strength of the prejudice and the degree of variation, it would show up more on the “nature” or “environment” side. Which is why I’m putting those words in scare quotes.
If race were a factor in twin studies, I think it would show up only in shared environment, since it differs between families but never within families (and is not differently different in MZ vs. DZ twins). That means it would not show in “heredity”, unless we’re talking about interracial couples with two children, each of whom by coincidence got a very different number of genes from the parents’ two races—I think this is rare enough not to matter in real life studies.
Your point stands about the general role of these kinds of things, I just don’t think it’s counted that way in the twin studies we actually have.
You’re right about beauty etc, though. Genetic studies are most informative about interventions to change individuals’ standings relative to other individuals, not about interventions to completely change the nature of the playing field.
But I think it would, unless I’m misunderstanding. If the world is (uniformly) biased against blacks, then the genes for “blackness” would be correlated with reduced outcomes, with no environmental effects since all environments are equally prejudiced.
For the effect to show up in environment, you’d have to have varying environments with different levels of prejudice; if the differences are pronounced enough, then you’d start seeing racial variations on the environmental side.
In a world where it was indeed perfectly even, lets say a world with a highly regimented system of prejudice where everyone’s skin tone is carefully measured and restrictions were then applied across the country.
But if prejudice isn’t perfectly even or measuring the same things then you’d expect it to vary.
If one twin grows up in a town where most of the residents still oppose miscegenation while the other ends up in a town with far less prejudice then the difference is going to show up as environmental.
Or if they have the same accent and same skin tone but one grows up in a town where people are more prejudiced about cultural markers like accent and dress while the other grows up in a town where they care more about biological markers the difference would show up as environmental.
Also it’s common to run PCA when dealing with samples from different ethnic origins to make it easy to spot when you’ve simply flagged up a variant linked to one group.
Examples:
http://www.genesandhealth.org/sites/elgh.mrmdev.co.uk/files/styles/380/public/Screen%20Shot%202015-02-26%20at%2010.28.28.png?itok=PyhQvYTn
https://static-content.springer.com/image/art%3A10.1186%2F1753-6561-5-S9-S116/MediaObjects/12919_2011_Article_1167_Fig1_HTML.jpg
If your flagged variant overlaps almost totally with only one group then it can be a sign that your analysis has been confounded though overlapping a little more with one group than with others is to be expected.
Yep. And depending on both the strength of the prejudice and the degree of variation, it would show up more on the “nature” or “environment” side. Which is why I’m putting those words in scare quotes.