[HN Gopher] Heritability of intrinsic human life span is about 50%
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Heritability of intrinsic human life span is about 50%
Author : XzetaU8
Score : 127 points
Date : 2026-02-01 12:13 UTC (2 days ago)
(HTM) web link (www.science.org)
(TXT) w3m dump (www.science.org)
| Enginerrrd wrote:
| 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 wrote:
| 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
| paulnpace wrote:
| As many of the health nutters say, the goal is "live well,
| drop dead."
| droopyEyelids wrote:
| It's a remarkable tragedy how many people don't understand
| your point.
|
| 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.
| techdmn wrote:
| I'm sorry that happened.
| faeyanpiraat wrote:
| 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 wrote:
| 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.
| intrasight wrote:
| One of the most consistent health research findings Ive
| heard in recent years is the benefits of weight training
| for older adults. Hopefully the message is being
| received.
| klik99 wrote:
| This plus stretching / yoga has been amazing as I'm
| entering my 40s. For a while I was just lifting and I had
| strong muscles but they were short and tight. Not everyone
| has that problem, but just noting strong muscles are half
| the picture, being strong and flexible makes life feel
| effortless and years of being a desk jockey.
| stalfie wrote:
| It is probably more than half the story. Health span is
| strongly correlated to life span, although not completely.
| The median "health span gap" is about 10 years, and has
| widened by roughly one year over the past 20 years. However,
| this is probably just due to an aging population and not
| necessarily from any factors you can control fully.
|
| I wouldn't be surprised if "health span" (although defining
| it is difficult) exactly mirrors the inheritability pattern
| of mortality.
| lm28469 wrote:
| > The median "health span gap" is about 10 years
|
| 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
| circlefavshape wrote:
| My Dad (age 81) tore his rotator cuff splitting wood
| recently. It's slow to heal and he's in a lot of pain which
| (along with his Alzheimer's) is _really_ getting him down.
|
| Maybe even if you're still fit and strong in your 80s you
| should let someone else split your wood for you
| Sohcahtoa82 wrote:
| Yup.
|
| 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.
| Merad wrote:
| My dad died at the end of last year, and was not too
| different from your grandma. For him the main problem was
| chronic pain from his failing body. Even fairly powerful
| opioids from a pain management doctor only helped a bit.
| Basically all he could do was sleep, eat meals, and sit in
| his chair in pain.
|
| 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.
| amanaplanacanal wrote:
| Something we youngsters (I'm 69) may not realize is that
| people in assisted living still have friends and
| frequently even sex lives while they are there. They
| read, play games, and watch movies, just like us. They
| might not be able to do all the things they could when
| they were younger, but their lives are not necessarily
| over.
| niemandhier wrote:
| I am looking forward to playing 3 decades of great
| computer games once I am too old to go out into the woods
| or do martial arts.
|
| I love gaming, but I am still too young to do it
| properly.
| nkrisc wrote:
| Of course, some truly do "live" there, and good for them.
|
| 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.
| baxtr wrote:
| 100% now that I get older I observe the even older people I
| know.
|
| Some live a very painful and limited life. Others are 85+ and
| still go out to run, play soccer etc. Amazing to see.
| gus_massa wrote:
| Life span is easier to measure. You get the offial birth
| dates table, you get the official death dates table, you just
| substract the numbers and call it a day.
| its_ethan wrote:
| 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 wrote:
| 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).
| xenadu02 wrote:
| Some epigenetic effects are semi-heritable too, eg maternal
| exposure can be transmitted. That's in addition to
| environmental effects like you mentioned. Two otherwise
| identical cohorts can inherit the same genetic
| predisposition for depression where one manifests and
| another does not entirely due to their circumstances.
|
| Evolution is just super super messy.
| UltraSane wrote:
| 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.
| zahlman wrote:
| > 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).
| D-Machine wrote:
| Lifespan is a quite skewed distribution, so the SD looks
| large because it is in fact a poor summary of the bulk of the
| distribution. The actual part we care about for age-related
| mortality is narrower than such an SD would imply if we had a
| normal distribution (simple image example:
| https://biology.stackexchange.com/a/87851).
| jjk166 wrote:
| > at least if one corrects for preventable accidents and
| other such things
|
| 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.
| DavidSJ wrote:
| One note: the standard deviation of the remaining effects would
| be sqrt(1/2) as large, not 1/2 as large. So more like 8.5-10.5
| years.
| D-Machine wrote:
| It is almost never reasonable to assume normality and make
| calculations like this. This is particularly the case when you
| are dealing with lifespan, which isn't normally-distributed
| even in the slightest. The actual ranges are likely smaller
| than you are stating here, and variance is just not a very
| practical or interpretable metric to use when dealing with such
| a skewed distribution.
|
| 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...
| rzmmm wrote:
| Environmental effects are not necessarily modifiable. It
| includes randomness, background radiation, unknown risk
| factors, anything which is not genetic.
| emp17344 wrote:
| 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...
| dash2 wrote:
| For a counterpoint to Sasha's view, you should probably check
| out https://open.substack.com/pub/astralcodexten/p/the-good-
| news...
| emp17344 wrote:
| Anyone who cites Jordan Lasker and Kierkegaard on
| heritability discussions is not someone you should take
| seriously.
| dash2 wrote:
| I work in the field and I think he is quite good at
| providing a fair layman's overview. He's also famous (or
| notorious) for having few barriers in terms of who he
| reads/responds to.
| logicallee wrote:
| tangentially, readers may be interested in this paper:
| https://stateofutopia.com/papers/1/evolving-brains-cull-long...
|
| (you can reproduce its results yourself in a few minutes).
| mlhpdx wrote:
| Shorter lifespans drive faster evolution. That was taught in
| basic biology and we, as a society, know it all too well
| (infectious diseases).
|
| It's difficult to square obsession with a long life with a
| healthy humanity.
| wizzwizz4 wrote:
| Faster evolution does not necessarily translate to better
| outcomes. Exhibit A: the respiratory capabilities of the
| brachycephalic pug. Exhibit B: the rabbit fear response -
| they can get so terrified that they break their own spines
| trying to escape. Exhibit C: every creature with a hybrid r/K
| reproductive strategy involving child- or sibling-
| cannibalism.
| mlhpdx wrote:
| > Faster evolution does not necessarily translate to better
| outcomes.
|
| For individuals, of course yes. But for populations? Also
| yes, but temporarily as dead-ends (A), or inconsequential
| stopovers (B), or distasteful (C).
| moi2388 wrote:
| Wait. They studied twins, removed accidents etc. But wouldn't
| this lead to overestimation of heritability due to shared
| environment?
| Insanity wrote:
| Yeah I'd take this study with a spoon of salt. As with many
| human studies, it's hard to control for all factors.
| Someone wrote:
| 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.
| tptacek wrote:
| The obvious problem you run into with twins raised apart is
| that there in fact aren't many twins who are raised apart.
| pinkmuffinere wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| GenBiot wrote:
| 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.
| JoeAltmaier wrote:
| Rats. I have ancestors that died at 97, others at 81. Some even
| younger. So, no telling.
| exe34 wrote:
| do you know what they died of? car accidents are probably less
| heritable, unless they're caused by heritable rash behaviour...
| JoeAltmaier wrote:
| Cancer mostly. Except Mom. She died of heart failure at 97.
| That's mostly, tired of living so long. She gave up.
| el_benhameen wrote:
| Unfortunately all of my male relatives suffered from hit by a
| bus itis.
| bluGill wrote:
| Still that is above average. I'm average, some ancestors died
| at 65, others 97, averaging out to around 80.
| sinenomine wrote:
| 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.
| c-fe wrote:
| 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)?
| wendgeabos wrote:
| 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?
| observationist wrote:
| 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.
| monknomo wrote:
| the more little old ladies around, the easier it is to raise
| kids.
| ertgbnm wrote:
| 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.
| colechristensen wrote:
| You can make it broader and simplify:
|
| 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.
| seydor wrote:
| It's probably not that useful (evolutionarily) beyond some age.
| Old people consuming resources without adding anything or
| holding back societies.
| parineum wrote:
| 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.
| vixen99 wrote:
| Given the opportunity, one wonders what you'd like to do with
| 'old people consuming resources without adding anything and
| supposedly 'holding back societies'. Earlier in the 20th
| century a significant cohort of intellectuals had decided
| ideas on this and the earlier generations.
|
| 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...
| kibwen wrote:
| Note that evolution isn't about individuals, it's about genes
| (which we should further note is more than just DNA, but that's
| a different discussion). If it weren't valuable for humans to
| live _at all_ without being fertile, then the average age of
| menopause and the average age of death would likely be much
| closer together. As it turns out, the human genes that were
| best able to pass themselves along were those that kept old
| people around despite being infertile, presumably to the
| benefit of helping to raise grandchildren, among other things.
| nikitau wrote:
| In (quantitative) genetics literature, heritability is usually
| defined (simplifying a bit) as the proportion of variance of a
| trait (lifespan, height, etc), in a population, that can be
| explained by genetics. The rest, by environmental factors, or
| error.
|
| If height were a 100% heritability means that all differences
| in height between individuals would be explainable by genetics.
| tptacek wrote:
| * correlated with genetics.
| jjk166 wrote:
| It's not useful. Indeed that's likely why we die of old age -
| there is no selective pressure to remove harmful mutations that
| don't reduce your ability to pass on your genes so such harmful
| mutations just accumulate over many generations. You might have
| a mutation that will cause your heart to rupture at age 150,
| but you'll never know it because you'll die of something else
| first.
|
| 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.
|
| https://pubmed.ncbi.nlm.nih.gov/3113991/
| slashdave wrote:
| We're social animals. Anything that benefits the extended
| tribal unit is advantageous. Adults beyond child-bearing age
| contribute significantly to child raising, education,
| leadership etc of the entire tribe.
|
| Similar effects are seen in other species
|
| https://www.nature.com/articles/s41467-018-05515-8
| pfdietz wrote:
| Seemingly due to reduction in extrinsic factors affecting
| lifespan.
| MichaelRo wrote:
| There's also some wisdom in that if you make kids later in life,
| you pass them the genes to survive (with 50% probability it
| seems) up to that age.
|
| 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" :)
| nerdralph wrote:
| There's a lot of genes that impact lifespan, both good and bad.
| For example my father has hereditary hemochromatosis due to 2
| copies of the HFE C282Y mutation. He was diagnosed in his 50's,
| so I'd expect the damage it did to his body to impact lifespan.
|
| 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).
| vondur wrote:
| It's interesting on my mother's side of the family, most everyone
| lived well into their 80's and 90's. The execution being for my
| Mom and her sisters who smoked heavily. Her brothers both died in
| their 60's but were in the Vietnam war and were definitely
| exposed to Agent Orange and both had brain cancer. My dad lived
| until nearly 80 after smoking since he was 12 years old and 2-3
| packs per day.
| csours wrote:
| I know enough about heritability to know that the science people
| use words differently than I expected, but not enough to explain
| that so here's someone's article about it:
|
| https://dynomight.net/heritable/
| D-Machine wrote:
| Heritability IMO falls into the same bin as
| "standardized/relative effect sizes" (e.g. correlation
| coefficients, Cohen's d, odds-ratios, "explained variance",
| relative risk, etc), in that a division / re-scaling is
| introduced to supposedly increase interpretability, but, in
| reality, this has precisely the opposite effect.
|
| 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.
| Imnimo wrote:
| >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?
| derbOac wrote:
| 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.
| laughing_man wrote:
| I thought the implication was lifestyle isn't as important as
| we previously believed.
| tgv wrote:
| On average! Start drinking a lot and find out.
| dash2 wrote:
| 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.
| marcosdumay wrote:
| 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.
| cortesoft wrote:
| 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.
| trehans wrote:
| But randomness comes from the environment, no?
| nextos wrote:
| 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.
| macleginn wrote:
| The 50% number is a bit mysterious, but if I understand the text
| of the article correctly, it essentially means that if we do not
| account for the noise added by accidents and such, we get a
| Pearson correlation of life expectancies of monozygotic twins of
| ~0.23. If we correct for accidents, the correlation rises to 0.5,
| hence 50% (with some further analysis they go up to 0.55, hence
| "above 50%" in the abstract). Now, in practical terms, this means
| that, given a MZ twin who died recently of natural causes, we
| could obtain an estimate for ourselves, but only if we make
| additional assumptions. A correlation coefficient alone is not
| very informative.
| NoMoreNicksLeft wrote:
| >Now, in practical terms, this means that, given a MZ twin who
| died recently of natural causes, we could obtain an estimate
| for ourselves,
|
| 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.
| accidentallfact wrote:
| The problem with twin studies:
|
| 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.
| mjburgess wrote:
| There's serious issues with heritability research in general,
| it's observability stuff -- not experimentation, so imv, its at
| best proto-science, and in many cases plainly pseudoscience.
| "Heritability" itself has little to do with whether something
| is inherited, and speaks only to correlation with genes. Since
| we have a vast amount of genes which are shared for all sorts
| of reasons (ie., mating is based on shared culture, wealth,
| geography, etc.) -- the metric is mostly useless.
|
| 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
| rzmmm wrote:
| Geneticist would say it's intended design of twin studies. Your
| example doesn't show AIDS is a genetic defect, but that
| genetics may predispose/protect against it.
| rzmmm wrote:
| Genetics may predispose for nicotine addiction, obesity,
| alcoholism, etc. This is intended design of genetic studies which
| look at multiple genes, like twin studies, GWAS studies, etc.
|
| 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.
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