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Comment by Imnimo | Hacker News Reader

>By contrast, intrinsic mortality stems from processes originating within the body, including genetic mutations, age-related diseases, and the decline of physiological function with age

So we put genetic diseases in the bucket of intrinsic mortality and then found that intrinsic mortality has a heritable component?

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Yeah this paper came across to me basically as "if you ignore environmental causes of death, the heritability of death goes up"... which seems kind of circular.

I thought the implication was lifestyle isn't as important as we previously believed.

On average! Start drinking a lot and find out.

Yeah, it’s important to note that heritability is a statistic about today’s population, not a deep natural parameter that tells you about causality. Heritability of smoking went up when smoking became less socially approved, for example.

There's no prior reason to expect the cited conditions to have any specific relation to genetics. Any of them could easily be caused or accelerated by environmental conditions.

And, in fact, it looks like they half-of-are.

Not necessarily. It could be the case that randomness plays a huge part in non-environmental caused deaths, and if that were the case we would see very little heritability.

But randomness comes from the environment, no?

No, you randomly get cancer since cancerous mutations happens randomly. Environment can just affect chance of getting cancer, it doesn't give you cancer directly and there is no way to completely avoid cancer risk.

For example even if you live the best life possible you will still have an inherent cancer risk based on your genes and that affects the random chance of you getting cancer, it isn't a clock that says exactly when cancer will happen.

Technically, sure, but that doesn’t mean it is related to anything observable about your environment.

I really like everything Uri Alon (last author) publishes, but these types of studies have a history of inflating genetic contributions to phenotypes. Decoupling genetics from environment is not easy as they are both highly correlated.

In fact, the article discussion states: "Limitations of this study include reliance on assumptions of the twin design, such as the equal environment assumption". My take on this is that the main result of the article is probably true, but the 50% figure is likely to be inflated.

I hit the jackpot with the ultrasound technician who spoke passionately about what she believed about lifestyle risk for cardiovascular conditions and she believed quite strongly that heart disease runs in families more because lifestyle runs in families than because of genetics. She's not at the top of the medical totem pole but I can say she inspired me to take responsibility for my health than the specialist who I talked to about the results.

Actually the opposite is true.

If the environment was significantly more varied in health impact between twin comparisons than expected, then the correlations they found under estimate the genetic component.

Noise weakens correlation. Removing noise strengthens correlations.

Some randomness is part of the signal being studied, and some is undesired measurement noise to be controlled for. And it is only the latter that is beneficial to be carefully removed or otherwise controlled for.

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