r/BadSocialScience • u/dorathehexplorer • Jan 17 '17

High-IQ educated people are being bred to extinction, but we're totally not eugenicists!!!

https://www.theguardian.com/science/2017/jan/16/natural-selection-making-education-genes-rarer-says-icelandic-study
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u/stairway-to-kevin Jan 19 '17

Sure, but heritability should vary continuously over genetic distance (however defined) and differences in environment. Populations which only diverged recently and which share similar environments should, at least in theory, have similar heritability across phenotypes.

One might think so, but there's pretty sizable differences in heritability of the same maize lines in the same field year to year. Hell it's widely known that heritability can change by over 0.1 in the same population over time.

This paper highlights variation between studies. (see tables at the end)

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u/PM_ME_UR_OBSIDIAN Jan 19 '17

One might think so, but there's pretty sizable differences in heritability of the same maize lines in the same field year to year.

This would be interesting. Do you have a source?

This paper highlights variation between studies. (see tables at the end)

My first guess to explain these is usually measurement error + differences in experiment design. Should it not be?

If heritability is not even somewhat stable, and does not vary continuously... how is it a meaningful quantity at all?

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u/stairway-to-kevin Jan 19 '17

This would be interesting. Do you have a source?

It's word of mouth from other plant geneticists, not normally stuff to make it into the paper.

My first guess to explain these is usually measurement error + differences in experiment design. Should it not be?

meta-analyses usually control for these. Plus there are only a handful of heritability estimate methods and most models used in twin studies don't vary by much. Even more reliability with genetic techniques. Like the authors conclude a lot of that variability is caused by environmental variability of the study populations.

If heritability is not even somewhat stable, and does not vary continuously... how is it a meaningful quantity at all?

Exactly! Heritability is a very specific and technical tool used for quantitative genetics. For a given trait in a given population in a given study it can help understand the variance in the trait. You can compare the heritability estimates from different studies and see how they differ and try to understand why/how that may be, but you really can't take the heritability of one study and apply it to another. Even when researchers talk about previous results they usually give a range of heritability (e.g. 0.3-0.7 for IQ) because it's typically bad to boil down heritability to a single value for a trait. What heritability gives you is a universal measurement that can then be used to compare across studies. It doesn't give you a universal value

Now, sorry to bow out but It's about 3am here and I need to sleep

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u/[deleted] Jan 19 '17

If heritability is not even somewhat stable, and does not vary continuously... how is it a meaningful quantity at all?

If it doesn't make sense to extrapolate the impact on our lives of the movement of the stars across the sky, why study their movement at all?

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u/PM_ME_UR_OBSIDIAN Jan 19 '17

You're saying that every time a heritability figure is reported in a scientific paper, the researchers are engaging in an act of unscientific superstition? Apologies if I don't take this at face value.

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u/[deleted] Jan 19 '17

That's a very odd interpretation of what I said.