Comment by IshKebab | Hacker News Reader

Comment by IshKebab | Hacker News Reader

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> Heritability has a very specific meaning in quantitative genetics [1]

Literally the first paragraph of that page is

> Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of heritability can be expressed in the form of the following question: "What is the proportion of the variation in a given trait within a population that is not explained by the environment or random chance?"

That matches what I assumed it meant, and it seems like OP and the post are arguing that that is some kind of surprising interpretation.

> OK, but check this out: Say I redefine “hair color” to mean “hair color except ignoring epigenetic and embryonic stuff and pretending that no one ever goes gray or dyes their hair et cetera”. Now, hair color is 100% heritable. Amazing, right?

Uhm, no. That is exactly what I (and I think most people) would expect the answer to be.

> That matches what I assumed it meant, and it seems like OP and the post are arguing that that is some kind of surprising interpretation.

The unintuitive part is that in quantitative genetics, heritability is defined in terms of variance in traits at the population level, not as the passing of traits from parents to offspring (that would be heredity [1]). Of course, I may have misinterpreted what you said in your OP when you cited the wiktionary definition of "[g]enetically transmissible from parent to offspring", and if so, I apologize, but at the time it seemed to me that you were talking about heredity.

> Uhm, no. That is exactly what I (and I think most people) would expect the answer to be.

What the article is talking about is that if you fix Var(E) = 0, then Var(P) = Var(G) in the standard heritability model, i.e. all phenotypic variance is explained entirely by genotypic variance (because in that model, Var(P) = Var(G) + Var(E)).

Fun fact (even if only tangentially unrelated): In Western countries, wearing glasses is a highly heritable trait, because wearing glasses is a strong proxy variable for refractive error [2], such as nearsightedness, which is highly heritable. It is often brought up as another example of how the quantitative genetics definition does not match conventional use of the word.

[1] https://en.wikipedia.org/wiki/Heredity

[2] https://en.wikipedia.org/wiki/Refractive_error

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