In case anyone was curious like me: the standard deviation of lifespan is ~12-15 years in developed countries.
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 1 hours ago [-]
Lifespan is not even half the story though, health span is much more important. Your life is completely different if you can ski or split your own wood at 80+ vs being barely able to use stairs at 50. Both might die at 90 but one "lived" 30 years more
faeyanpiraat 37 minutes ago [-]
Yeah, been working in IT since forever (sitting work all day), but started lifting recently and it already made remarkable improvements in my wellbeing. Should've started sooner of course, but I'm still well in time.
vixen99 7 minutes ago [-]
Lot of people think it's a niche exercise activity and it shouldn't be - for all ages including those in their 80s and 90s according to reports.
droopyEyelids 57 minutes ago [-]
It's a remarkable tragedy how many people don't understand your point.
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.
paulnpace 1 hours ago [-]
As many of the health nutters say, the goal is "live well, drop dead."
its_ethan 1 hours ago [-]
This is a nice example/re-stating of what the heritability % "means" here.
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 1 hours ago [-]
Heritability is a pretty funky concept because it's contextual to a certain point in time, environment, and population, effectively.
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).
zahlman 53 minutes ago [-]
> the standard deviation of lifespan is ~12-15 years in developed countries.
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).
UltraSane 1 hours ago [-]
Lifespan isn't as important as healthy lifespan. Lifestyle can mean the difference between being able to complete an Ironman triathlon at age 80 vs being bedbound.
c-fe 50 minutes ago [-]
How is heritabiltity of life span useful if by the time the lifespan becomes known (eg at 80yrs old) the inheritance is not possible anymore (eg menopause)?
observationist 36 minutes ago [-]
Heritability acts on lineages, not individuals (in general, not always) - a good rule of thumb is that traits that benefit 3 or more generations of a family have a good shot at being propagated. In this case, the advantage (of both menopause and longevity) is increased well-being of the tribe, ampliyfing the positive effects of culture and stability. Wisdom of the elders is implicit to the genetics. This is a tradeoff with the cost in resources; at some point the cost to keep someone around might exceed the benefit, but from an evolutionary standpoint, the accounting is over a lifetime; in a relatively stable environment, genes that improve longevity and healthspan will be reinforced by the positive feedback loops of culture and nurture and civilization and technology. Menopause is also prevalent in orcas and a handful of other mammals - and older females help rearing and protecting babies, and so forth, with a protoculture providing that feedback loop.
ertgbnm 30 minutes ago [-]
Explanation I've heard in popscience books:
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.
wendgeabos 36 minutes ago [-]
What is the question you are asking? What does "useful" mean, in other words? How does it contribute to the reproductive success of the offspring?
seydor 20 minutes ago [-]
It's probably not that useful beyond some age. Old people consuming resources without adding anything or holding back societies.
parineum 10 minutes ago [-]
Those old people used to be young and helped pay for their parents and grandparents to live into old age. Part of being young and productive is helping take care of those less able than you, including the elderly.
Unless you're volunteering to work for 40 years then be executed on retirement, I think you should delete that comment and that thought from your mind.
monknomo 34 minutes ago [-]
the more little old ladies around, the easier it is to raise kids.
12 minutes ago [-]
sinenomine 1 hours ago [-]
This finding rectified my mental model of longevity after a long, perplexing period where longevity was estimated to be much less heritable than expected when comparing to other studied traits.
emp17344 1 hours ago [-]
Keep in mind this research is based on correcting twin study heritability estimates for confounding effects. However, new research shows that heritability estimates derived from twin studies are themselves dramatically inflated: https://open.substack.com/pub/theinfinitesimal/p/the-missing...
pfdietz 44 minutes ago [-]
Seemingly due to reduction in extrinsic factors affecting lifespan.
JoeAltmaier 1 hours ago [-]
Rats. I have ancestors that died at 97, others at 81. Some even younger. So, no telling.
exe34 1 hours ago [-]
do you know what they died of? car accidents are probably less heritable, unless they're caused by heritable rash behaviour...
JoeAltmaier 26 minutes ago [-]
Cancer mostly.
Except Mom. She died of heart failure at 97. That's mostly, tired of living so long. She gave up.
moi2388 1 hours ago [-]
Wait. They studied twins, removed accidents etc. But wouldn’t this lead to overestimation of heritability due to shared environment?
Someone 39 minutes ago [-]
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.
Insanity 1 hours ago [-]
Yeah I’d take this study with a spoon of salt. As with many human studies, it’s hard to control for all factors.
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.
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.
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%?
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).
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).
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.
Unless you're volunteering to work for 40 years then be executed on retirement, I think you should delete that comment and that thought from your mind.
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.
(you can reproduce its results yourself in a few minutes).
It’s difficult to square obsession with a long life with a healthy humanity.