Wait. They studied twins, removed accidents etc. But wouldn’t this lead to overestimation of heritability due to shared environment?

▲

Someone 8 hours ago | parent | next [-]

FTA: “We use mathematical modeling and analyses of twin cohorts raised together and apart”

So, take one cohort of twins raised together and see how well their life spans correlate.

Take another cohort of twins separated at or near birth and do the same.

Then, do some math magic with both to estimate heritability.

▲

GenBiot 6 hours ago | parent | next [-]

This is incorrect. Twin studies typically compare MZ twin similarity against (same sex, usually) DZ twin similarity. Assuming that there is nothing special about MZs for the trait (e.g. in this case if MZ twins lived longer by virtue of being MZ twins), you can estimate heritability free of shared environments.

▲

tptacek 7 hours ago | parent | prev | next [-]

The obvious problem you run into with twins raised apart is that there in fact aren't many twins who are raised apart.

▲

pinkmuffinere 6 hours ago | parent [-]

From tfa

> We estimated uncorrected heritability (uncorrected for extrinsic mortality) (materials and methods) in three independent ways: (i) MZ twins reared apart (n = 150), (ii) DZ twins reared apart (n = 371), and (iii) MZ versus DZ twins reared together (196 MZ, 325 DZ)

This is from _one_ of the datasets they examined, but there were also two others. n=150 twins reared apart in their small category, or n=520 twins reared apart total is the lower bound of data they had, and even that is not too shabby imo

▲

tptacek 6 hours ago | parent [-]

I don't have an opinion to offer here other than the intrinsic limitations of studies that depend on twins raised apart (that there aren't many of them). It's an unusual instance of a stat where the obvious concern with the premise is underappreciated rather than overappreciated. I've got nothing on MZ/DZ controls.

	▲	pinkmuffinere 6 hours ago \| parent [-]
		ah I see, you're commenting on the general difficulty, not necessarily saying this study's results are bad due to the limitation. My apologies, I don't think we disagree.

▲

moi2388 7 hours ago | parent | prev [-]

Yes but those aren’t random samples. Children not raised with their birth parents had different circumstances. As did children who got split up, and families adopting children is also a selection bias.

▲

Insanity 8 hours ago | parent | prev [-]

Yeah I’d take this study with a spoon of salt. As with many human studies, it’s hard to control for all factors.