I think the studies which find a single gene variant which would have large impact on lifespan would be interesting. Not sure if variants like that exist though.
In my case I don't have it (I'm just a genetic carrier). If I did have the genotype and took the necessary dietary measures to avoid the phenotype, then it likely wouldn't impact lifespan.
On one hand you can argue a heritable disease like HHC has an impact on lifespan, but with genetic testing and treatment you can argue it doesn't impact lifespan (or it's impact is significantly mitigated).
So we put genetic diseases in the bucket of intrinsic mortality and then found that intrinsic mortality has a heritable component?
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.
1. There are genetic mutations that make you immune to HIV.
2. Monozygotic twins will both be immune, or not immune, while dizygotic twins may be either, one can be immune, while the other one could get AIDS.
3. Thus, a twin study would likely show that AIDS is a genetic defect.
So if you're in the kind of family that dies of cancer at 30, and make kids at 25, perspectives don't look great.
Now, not to these people shouldn't make kids but perhaps, choose a spouse whose family dies on average at 60+?
Marry "up", not "down" :)
Uh... am I misreading your comment, or are you suggesting that when your identical twin dies of non-accidental death, you can be pretty sure you're about to croak in the next wee days or weeks yourself? Very difficult to engineer that alarm bell (you either have a twin, or not), and too damned late to matter.
We should be stating something like a probability density interval (i.e. what is the actual range / interval that 95% of age-related deaths occur within), and then re-framing how much genetic variation can explain within that range, or something like it. As it is presented in the headline / takeaway, the heritability estimate is almost impossible to translate into anything properly interpretable.
https://biology.stackexchange.com/questions/87850/why-isnt-l...
(you can reproduce its results yourself in a few minutes).
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%?
Accents are highly heritable, since they always correlated with location which is always correlated with genes.
Even if you do these twin studies, you have to assume a model of how genes and the environment interact, and all such models are obviously false.
Thus even if you grant that heritability measures on high quality twin studies are 'sign correct', in the sense that they show P(genetic effect) > P(no genetic effect) -- any magnitude of this effect, or any theory of is, is more or less pseudoscience (unless there are experimental studies showing gene-trait mechanism).
For example, it is "obvious" that P(genetic effect) > P(none) for intelligence, since genes control the structure of the brain and body. But there is no evidence (I'm aware of...) that beyond provision of a functioning brain, our genetics play any role in intelligence stratification. ie., all correlation with task performance and IQ can be explained by correlations in the metal retardation / mental deficiency range.
This doesn't mean intelligence is very malleable beyond a certain age. My own views is that genes are basically providing functioning hardware to the womb, and after that point its early development (both pre-birth and probs up to at most 3yo) which locks in a lot of the observed intelligence stratification. This is a very different story than popularisers of IQ research communicate though, but be aware, none are very good scientists and most of this research is methodologically unfit
Maybe even if you're still fit and strong in your 80s you should let someone else split your wood for you
Some live a very painful and limited life. Others are 85+ and still go out to run, play soccer etc. Amazing to see.
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.
It’s difficult to square obsession with a long life with a healthy humanity.
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).
I'm not really afraid of getting old, but I'm afraid of becoming decrepit.
My grandma has been decrepit for over 5 years now. She can't walk and has no bladder or bowel control, so she just sits on the couch and shits herself all day. She's not living, she's merely surviving. She was living with my mom for a while, but my mom decided she couldn't handle it anymore and put her in an assisted living facility.
If I get to the point where I couldn't cook my own meals and wipe my own ass, just put a bullet in me. I do not fear dying, but I do fear spending years of my life not being able to actually do anything.
I wouldn't be surprised if "health span" (although defining it is difficult) exactly mirrors the inheritability pattern of mortality.
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.
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).
And, in fact, it looks like they half-of-are.
You can't really correct for these. Yes there are genuine accidents that will kill you under any circumstances, but for a lot of things both your odds of having an accident and the odds of surviving it are strongly linked to age. As a simple example, despite driving significantly less, the elderly get into more car accidents and suffer worse injuries in those accidents than people earlier in life. Only the age range of 15-24 has higher car accident fatality rates.
There is no such thing as death by old age. At most there are deaths in the elderly that don't get attributed to a specific cause (typically because of so many different things going on at once and no desire to cut up grandma after the fact to see which straw broke her back) which we tend to refer to as "died of old age" but it's not a recognized medical cause of death. People die of diseases, injuries, and various other things, many of which are strongly influenced by age but also heavily influenced by other factors.
You can set a cutoff point and say these things don't count as age related deaths whereas these others do. As long as you're consistent with these choices, you can learn something useful. But a wide enough net that is widely agreed to cover what we think of as aging is going to include a lot of other maladies, whereas a narrower selection criteria is probably going to yield wildly different results from one analysis to the next.
It depends on the definition, if you're even just 20kg overweight you're living a wildly different life than you'd have if you were fit, you're closing so many doors by default and making a bunch of things much harder than they should be, But you're still considered "healthy" here
Evolution is just super super messy.
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 feel similar to you, but I wonder if it's one of those those things where age changes your perspective. Dad was in assisted living and had several stints in rehab/nursing home facilities, and in both there were quite a few people with what I'd call poor quality of life who were still holding on to life.
Similar effects are seen in other species
It is possible though to selectively breed animals like flies for long lifespan. You wait to see how long one generation lives and cull the descendants of those that died early. It's inefficient but lifespan extensions of 50-60% have been demonstrated. One could imagine through gene editing that a species might be able to reap the benefits without the culling.
Heritability is a bit worse though because the variance is partitioned into three giant piles of mush, at least two of which piles are very poorly measured / controlled at all.
If height were a 100% heritability means that all differences in height between individuals would be explainable by genetics.
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.
For individuals, of course yes. But for populations? Also yes, but temporarily as dead-ends (A), or inconsequential stopovers (B), or distasteful (C).
> 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
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.
Related somewhat to this: 'The Intellectuals and the Masses' by John Carey makes for truly shocking reading.
Who? https://www.theguardian.com/books/2025/dec/14/john-carey-obi...
If you are interacting with a carrier of your genes at all while they still might reproduce, you are having an impact on their fitness and thus evolutionary pressure exists.
I love gaming, but I am still too young to do it properly.
And others just sit there waiting to die, unable to even feed themselves.
I saw plenty of examples of both when my grandmothers were in assisted living homes. Unfortunately my grandmothers both tended towards the latter case.
I suspect it won't be hair-trigger combat games in dark dungeons where every strike results in a blizzard of gems and stars flying around the screen while teenagers scream into the mic.
But if you like Sudoku and crosswords you'll probably be good. That's my jam anyway.