(you can reproduce its results yourself in a few minutes).
It’s difficult to square obsession with a long life with a healthy humanity.
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.
Healthy grandparents that are around to support their children and take care of grandchildren increase the fitness of the entire lineage by helping their children have more children and those grandchildren to be healthier/safer.
Enginerrrd•1h ago
So environmental effects, sleep, diet, lifestyle, etc (I.e. modifiable factors) maybe account for half of that, so like 6-7.5 years of variance. Which… sounds about right to me.
lm28469•1h ago
paulnpace•1h ago
droopyEyelids•39m ago
https://en.wikipedia.org/wiki/Disability-adjusted_life_year
Too many people think your life is a binary 'living or dead' when thats not the case at all. I didn't even understand it fully till I was hit by a car.
faeyanpiraat•19m ago
its_ethan•1h ago
I'm curious, with something like smoking/drinking, how you can be confident that you've untangled genetic predispositions to addiction or overconsumption from those "modifiable factors". I guess that's just captured within the 50% heritability? And if you could confidently untangle them, you might find heritability is higher than 50%?
morleytj•44m ago
An example I like is that if you measured the heritability of depression in 2015, and then you measured the heritability of depression in 2021, you would likely see changes due to environmental effects (namely, there's the pandemic/lockdowns and this could conceivably cause more people to experience depressive symptoms). Let's assume we make those measurements and the rate of depression did increase, and we could tie it causally to the pandemic or related events.
In that scenario, the heritability of depression would have decreased. I don't think anyone would argue there were massive genetic changes in that 6 year time period on a population scale, but the environment changed in a way that affected the population as a whole, so the proportion of the effect on the trait which is genetically explained decreased.
For something like lifespan in the above example, you can imagine that in a period of wartime, famine, or widespread disease the heritability would also decrease in many scenarios (if random chance is ending a lot of lives early, how long the tail of lifespan is influenced genetically is much less important).
Given that note, it's generally tricky to talk about whether heritability increases or decreases, but with more accurate estimates of how genetic predispositions form you could see the heritability of certain traits increase with the environment held stable, as there's certainly ones that may be underestimated or genetic factors that aren't currently accounted for in many traits.
*edit: I realized I never mentioned the other thing I wanted to mention writing this! since you mentioned what the percent heritability means here, I think the best way to think of it is just "the proportion of phenotypic variation for this trait in a measured population which is explained by genetic variation." So it's dependent on the amount of variation in several aspects (environmental, genetic, phenotypic).
UltraSane•1h ago
zahlman•35m ago
That seems rather higher than I would have expected, at least if one corrects for preventable accidents and other such things (that I would expect to shift the results away from a normal distribution).