I don't mean to spam but I've seen a previous post of yours suggesting you're open to some amount of self-advertising.
You said, "We are not assuming that genes are in Hardy-Weinberg equilibrium, whatever that is."
I was thinking of writing a post for a while on "whatever that is" and that's below. Hoping people interested in a post explaining the basics of heritability would also be interested in a post attempting a clear and precise explanation of Hardy-Weinberg Equilibrium:
Thanks! For anyone else reading this, I don't just tolerate but encourage self-promotion for anything that's topic or spiritually related. (This is both.)
I don't have any opinion about the general heritability debates that I feel comfortable sharing in public (yet). :) But I will say that after starting from a baseline of thinking everything is highly heritable, I learned a lot from reading Gusev, e.g. about some of the weaknesses of existing twin studies. So I think he provides some useful skepticism.
Sorry to question the hypothetical when you specifically said not to, but I'm curious and know nothing about this field: does the simplifying assumption of asexual reproduction really not matter at all? Seems like it should!
Maybe you could also do it by assuming the gene is on the y-chromosome, near-starvation is determined by fathers, and only manifests for baby boys. But... still seems like a distraction!
Oh, it certainly matters, because with sexual reproduction you can't think about people as having "tall" or "short" genes, but you have to consider lots of cases: Each parent and the baby can basically be SS, ST, TS or TT, so there are 4^3=64 cases to worry about instead of just four.
You can create an example where the same issue manifests while reflecting all that, but I wasn't able to figure out a way to do it without making everything much more complex. (At least, not other than my other fix of perfect assortative mating.)
The copy article on your site has a duplicate question for
> Say there’s an island where neither genes nor the environment influence height. Except, some people have a gene that makes them inject their babies with human growth hormone, which makes them 5 cm taller. How heritable is height?
Yes, similarly the table on short and tall genes registers correctly on the main website but not this substack post. Here it's like:
Baby genes Parent genes Food Height Short Short Lots 165 cm Short Tall Semi-starvation Less than 165 cm Tall Short Lots More than 165 cm Tall Tall Semi-starvation 165 cm
But all-in-all thanks Dynomight for this article! I love to see this kind of stuff.
Thank you! I have classical Ehlers Danlos Syndrome, and it's always been described as heritable. The definition I was working with was "present at birth" which is clearly not accurate. This makes a lot more sense. In all but one of the types of EDS, a mutation happens to one of the collagen genes, which makes connective tissue, like tendons, skin, and other soft tissue weak. I've always held the belief that there's little you can do to change or strengthen the collagen. If you have the mutation, and even if you're born in Asia, to parents who are deaf, or are adopted by parents without EDS; even if you take ballet classes as a child, are educated in 4 different languages, or grow up next to a nuclear power plant; even if you have surgery to fix a tendon, take collagen supplements, or do aquatic therapy every day, the 👏🏻 collagen 👏🏻 will 👏🏻 still 👏🏻 be 👏🏻 defective because the environment change doesn't matter. There are things we can do about the *symptoms* the weak collagen and connective tissue cause, like pain, hypermobile joints, GI troubles, etc. But unless we edit the gene, the condition will exist.
Sorry to hear about that! I don't know much about EDS, but what I do know is consistent with what you said, treatment is supportive and can reduce symptoms.
In the context of this essay, the only point I would make is that it doesn't follow simply from the technical definition of heritability that lifestyle changes can't improve things. Even if something is >99% heritable, that only means that *normal* lifestyle changes probably don't have much impact. But it doesn't prohibit the possibility that more unusual lifestyle changes could do something.
Anyway, we know lots about the causal mechanisms of EDS, and lots of interventions have been studied. So I think there's no reason to rely on the very crude measure of statistical heritability. It basically adds nothing when we already have studies of interventions.
Also, it's quite possible that when people say it's "heritable" they're using the normal English "heritable" rather than the technical ratio-based "heritable". That collision causes endless unnecessary confusion and is what I was complaining about here: https://dynomight.net/heritable/#:~:text=egregious
Hmm. Here is a true story. I was adopted at birth by young nitwits who successfully hid all the details of my birth until I was old enough to ask questions. The birth mother went into the hospital with the adoptive mother's name, so my birth certificate was phony. From a very young age, I "knew" that I was in the wrong tribe despite the superficial similarities in appearance [same skin color etc]. I knew how to read well before formal schooling began without being taught. The tribe didn't value that and refused requests to go to the public library after I had read most of what was available in the school library. The tribe's motto, "People like us don't...fill in the blank". I heard this often about so many things: read books, magazines, watch the news, go to college, talk about 'things', ask questions, learn to speak other languages, and on and on. Eventually, compassionate public school teachers tried to get me into college at age 15, but the tribe refused to cooperate because people like us...don't. Finally a tribal member told me the story of the illegal adoption, and I understood-of course I didn't fit in this tribe. It was like the egg of a swimming bird had been put in a chicken's nest. The chicken would never understand why one of the chicks was able to swim-heritability. I wasn't from them, didn't have to struggle to be one of them. I swam away. Later in a college genetics class, I understood more but was still tribeless. From this personal experience/small sample size, I think that heritability is everything. The environment is not nothing, but the math doesn't work.
Thank fuck, I was gonna write a post on this but now I can just link this. Wonderful. Mainly for the reason of pointing out that high heritability doesn’t imply that traits can’t be intervened on.
A good way of doing this is just pointing out muscle mass and strength have really high heritability, but going through the actual definitions is ideal!
Ah, perhaps I should have used that as an example! I'd guess that some non-negligible fraction of the heritability of muscle mass is driven by personality differences, which are in turn driven by genes. Genes that drive you towards exercise or a physical work will tend to make you stronger even though those are choices. So if you're choosing if you want to exercise it's completely irrelevant.
I’ve read that the tendency to be an active adult (where active = regular participation in sport/gym attendance/etc) has strong heritability, and results in about 25% of adults engaging in said activities, and the rest being notably less inclined to do so - but perhaps still responsive to other factors, like the fun and sociability of team sports, and/or local cultural value of same. I often ponder this when I see advertising which encourages adults to be active - will pulling that environmental lever make a difference for the 75%?
I don't mean to spam but I've seen a previous post of yours suggesting you're open to some amount of self-advertising.
You said, "We are not assuming that genes are in Hardy-Weinberg equilibrium, whatever that is."
I was thinking of writing a post for a while on "whatever that is" and that's below. Hoping people interested in a post explaining the basics of heritability would also be interested in a post attempting a clear and precise explanation of Hardy-Weinberg Equilibrium:
https://nickpbailey.substack.com/p/what-hardy-weinberg-equilibrium-is
Thanks! For anyone else reading this, I don't just tolerate but encourage self-promotion for anything that's topic or spiritually related. (This is both.)
Did you mean to add the exponent 2 to the cm label when discussing the variance of height?
Yup, variance has units of the base quantity squared!
Thanks. Obviously statistics and probabilities are not my strong suit
Thanks for this.
Since you've mentioned Gusev, where do you stand on the recent missing hertability debates?
Are you planning another post on that (I sure hope so)?
I don't have any opinion about the general heritability debates that I feel comfortable sharing in public (yet). :) But I will say that after starting from a baseline of thinking everything is highly heritable, I learned a lot from reading Gusev, e.g. about some of the weaknesses of existing twin studies. So I think he provides some useful skepticism.
Sorry to question the hypothetical when you specifically said not to, but I'm curious and know nothing about this field: does the simplifying assumption of asexual reproduction really not matter at all? Seems like it should!
Maybe you could also do it by assuming the gene is on the y-chromosome, near-starvation is determined by fathers, and only manifests for baby boys. But... still seems like a distraction!
Oh, it certainly matters, because with sexual reproduction you can't think about people as having "tall" or "short" genes, but you have to consider lots of cases: Each parent and the baby can basically be SS, ST, TS or TT, so there are 4^3=64 cases to worry about instead of just four.
You can create an example where the same issue manifests while reflecting all that, but I wasn't able to figure out a way to do it without making everything much more complex. (At least, not other than my other fix of perfect assortative mating.)
Interesting, are the pairs symmetric? Like does it matter which come from which side?
The copy article on your site has a duplicate question for
> Say there’s an island where neither genes nor the environment influence height. Except, some people have a gene that makes them inject their babies with human growth hormone, which makes them 5 cm taller. How heritable is height?
Thanks, fixed! (I think I was moving this around and debating the right order.)
Yes, similarly the table on short and tall genes registers correctly on the main website but not this substack post. Here it's like:
Baby genes Parent genes Food Height Short Short Lots 165 cm Short Tall Semi-starvation Less than 165 cm Tall Short Lots More than 165 cm Tall Tall Semi-starvation 165 cm
But all-in-all thanks Dynomight for this article! I love to see this kind of stuff.
Thanks fixed. (Substack somehow still doesn't support tables, so I need to copy-paste them as images, which I apparently often fail to do correctly.)
Thank you! I have classical Ehlers Danlos Syndrome, and it's always been described as heritable. The definition I was working with was "present at birth" which is clearly not accurate. This makes a lot more sense. In all but one of the types of EDS, a mutation happens to one of the collagen genes, which makes connective tissue, like tendons, skin, and other soft tissue weak. I've always held the belief that there's little you can do to change or strengthen the collagen. If you have the mutation, and even if you're born in Asia, to parents who are deaf, or are adopted by parents without EDS; even if you take ballet classes as a child, are educated in 4 different languages, or grow up next to a nuclear power plant; even if you have surgery to fix a tendon, take collagen supplements, or do aquatic therapy every day, the 👏🏻 collagen 👏🏻 will 👏🏻 still 👏🏻 be 👏🏻 defective because the environment change doesn't matter. There are things we can do about the *symptoms* the weak collagen and connective tissue cause, like pain, hypermobile joints, GI troubles, etc. But unless we edit the gene, the condition will exist.
Did I explain that correctly?
Sorry to hear about that! I don't know much about EDS, but what I do know is consistent with what you said, treatment is supportive and can reduce symptoms.
In the context of this essay, the only point I would make is that it doesn't follow simply from the technical definition of heritability that lifestyle changes can't improve things. Even if something is >99% heritable, that only means that *normal* lifestyle changes probably don't have much impact. But it doesn't prohibit the possibility that more unusual lifestyle changes could do something.
Anyway, we know lots about the causal mechanisms of EDS, and lots of interventions have been studied. So I think there's no reason to rely on the very crude measure of statistical heritability. It basically adds nothing when we already have studies of interventions.
Also, it's quite possible that when people say it's "heritable" they're using the normal English "heritable" rather than the technical ratio-based "heritable". That collision causes endless unnecessary confusion and is what I was complaining about here: https://dynomight.net/heritable/#:~:text=egregious
Hmm. Here is a true story. I was adopted at birth by young nitwits who successfully hid all the details of my birth until I was old enough to ask questions. The birth mother went into the hospital with the adoptive mother's name, so my birth certificate was phony. From a very young age, I "knew" that I was in the wrong tribe despite the superficial similarities in appearance [same skin color etc]. I knew how to read well before formal schooling began without being taught. The tribe didn't value that and refused requests to go to the public library after I had read most of what was available in the school library. The tribe's motto, "People like us don't...fill in the blank". I heard this often about so many things: read books, magazines, watch the news, go to college, talk about 'things', ask questions, learn to speak other languages, and on and on. Eventually, compassionate public school teachers tried to get me into college at age 15, but the tribe refused to cooperate because people like us...don't. Finally a tribal member told me the story of the illegal adoption, and I understood-of course I didn't fit in this tribe. It was like the egg of a swimming bird had been put in a chicken's nest. The chicken would never understand why one of the chicks was able to swim-heritability. I wasn't from them, didn't have to struggle to be one of them. I swam away. Later in a college genetics class, I understood more but was still tribeless. From this personal experience/small sample size, I think that heritability is everything. The environment is not nothing, but the math doesn't work.
Thank fuck, I was gonna write a post on this but now I can just link this. Wonderful. Mainly for the reason of pointing out that high heritability doesn’t imply that traits can’t be intervened on.
A good way of doing this is just pointing out muscle mass and strength have really high heritability, but going through the actual definitions is ideal!
Ah, perhaps I should have used that as an example! I'd guess that some non-negligible fraction of the heritability of muscle mass is driven by personality differences, which are in turn driven by genes. Genes that drive you towards exercise or a physical work will tend to make you stronger even though those are choices. So if you're choosing if you want to exercise it's completely irrelevant.
Agreed, I wonder if there has been research on that specifically? Heritability of inclination to exercise. Probably somewhere
I’ve read that the tendency to be an active adult (where active = regular participation in sport/gym attendance/etc) has strong heritability, and results in about 25% of adults engaging in said activities, and the rest being notably less inclined to do so - but perhaps still responsive to other factors, like the fun and sociability of team sports, and/or local cultural value of same. I often ponder this when I see advertising which encourages adults to be active - will pulling that environmental lever make a difference for the 75%?
heritability from twin studies seems to be around .5 at the highest, often lower
Excellent breakdown.
Shame that genetic variances in height are so controversial that it takes real bravery to talk about it in polite society.