Heritable != Molecular / Genetic Mechanism

There is a conflation of these terms in popular discourse that does a disservice to the field of statistical genetics, imo. There are mechanisms of inheritance that operate various length / time scales other than that of biological macromolecules. For example, if you tell me what language your parents natively speak I can tell you your primary language with >90% accuracy.

So before we start getting 3 replies deep into any thead, please remember that retrospective observational data measured with unqualified instruments is notoriously confounded and that we can barely infer causal structure in controlled functional genomics experiments (much less a GWAS of phewas). So let’s all please keep an open mind and not be so certain about our beliefs.

    > Almost all human traits are partly genetic and partly due to the environment and/or random. If you could change the world and reduce the amount of randomness, then of course heritability would go up.

It implies that the only environment that matters is either purely random (truly random accidents, circumstances) or non-systematic (results from non-linear interaction of environment and genes).

When stated that way it almost feels like a tautology because this is what genes exist to do in the first place. To control the interactions of their vessel and environment to the maximum degree. And from the perspective of an individual gene, all the other genes are part of the environment too.

    > There is no such thing as “true” heritability, independent of the contingent facts of our world.

Which I bet is very useful for some kind of technical work, but it's amusingly confusing to lay people.

The author goes on to critique its misuses but the textbook example to make clear "heritability" is not as obvious as it sounds is that by this definition human bipedalism heritability is near zero because there's near zero variance.

> Heritability of human lifespan is about 50% when extrinsic mortality is adjusted to be closer to modern levels.

I think by “accounting for confounding factors” they mean setting extrinsic mortality to the equivalent of zero contribution. So you’d expect it to be the asymptote left side.

0: especially enjoyed talking about typos and then writing “doing to go”. I like little jokes like that.

Yep, checks out.

Why is it applied to twins if genes are inherited from parent to child?

How readhedness is 100%? I understand Mendel study in school is simplification, but you can get all sorts of gene mixes in kids

https://en.wikipedia.org/wiki/Gompertz_distribution

My intuition is that the average genetic human potential, for traits that are ostensibly hierarchical, is higher and narrower than is usually accepted - which is uncomfortable for those whose ambitions require, either directly or by incidence, that most people don't reach that potential. Or, that they're not actually hierarchical traits at all; value depends on context (and is generally made up).

Oddly, the former is probably preferable to most, since, "There is no inherent value in dying old versus young," probably doesn't track for most people.

Seems like the author is doing some redefining here like he's accusing the paper's author.

Perhaps the statement was meant to mean "fulfillment of hereditary characteristics change when society changes" but it wouldn't be that hard to say it if that's what it was supposed to be...

For instance, it begins via:

"How heritable is hair color? Well, if you’re a redhead and you have an identical twin, they will definitely also be a redhead."

So, red hair is primarily caused, in most cases, by a defective enzyme involved in pigmentation. Wikipedia mentions it: https://en.wikipedia.org/wiki/Red_hair - you can read up on pubmed for that https://pubmed.ncbi.nlm.nih.gov/10326071/ and more recent articles. Now why is the claim "identical twins" must be redhaired? First it assumes that identical twins are fully identical on the genetic level. This is not the case, there are many differences. Statistically these are, of course, much less than when you compare many different people to one another usually. So it can be assumed that in most cases the "identical" twins (a better term would be monozygotic; note that even wikipedia here https://en.wikipedia.org/wiki/Twin defines the word incorrectly. Monozygotic does not say ANYTHING about "identical". Mono means one; zygotic means "from the zygote" or "derived from the zygote"). Of course in most cases the genes, if compared 1:1, will be identical. But this is not always the case, and it also depends a lot on the mutation at hand (or rescue mutations - see genetic cosuppression). So it COULD be that identical twins are NOT both redheads. One possibility is a simple spontaneous mutation at a nucleotide position that could restore functionality of at the least one enzyme mentioning above with regard to pigmentation. During DNA replication errors can also happen. The rate of error creation may be low for many reasons, but it is above zero, so it could happen.

That problem in the article could have been avoided if he would have chosen something else other than "they will definitely also be a redhead". Other users here on Hackernews also pointed out other incorrect or incomplete statements or assumptions made. This also ties into "definitions". Ultimately there is a much easier definition first: define max age span and average age span of cohorts. Then you need to define heritability with this regard. The claim of "more or less life span" when heritability is redefined, means that someone did a very poor, sloppy job beforehand already.

It seems incredibly disingenuous to lump together epigentics and hair dye when talking about heritability of hair color. We all know when we talk about inheriting hair color we're talking about natural hair color.

> his paper built a mathematical model that tries to simulate how long people would live in a hypothetical world in which no one dies from any non-aging related cause, meaning no car accidents, no drug overdoses, no suicides, no murders, and no (non-age-related) infectious disease.

Which is exactly what everyone means by lifespan in this context. No one on earth is trying to figure out how much genetics contributes to the odds of being hit by a bus.

> veryone seems to be interpreting this paper as follows:

>> Aha! We thought the heritability of lifespan was 23-35%. But it turns out that it’s around 50%. Now we know!

Which is the correct interpretation. Proper elimination of confounding factors is good science. The previous estimates were low because they weren't properly measuring what we are all referring to when we talk about lifespan.