PhilGoetz comments on She Blinded Me With Science - Less Wrong

13 Post author: Jonathan_Graehl 04 August 2009 07:10PM

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Comment author: barrkel 05 August 2009 01:29:40AM 3 points [-]

Have you actually read the linked-to article? Heritability != genetic control. The textbook example:

The textbook example is that (essentially) all of the variance in the number of eyes, hearts, hands, kidneys, heads, etc. people have is environmental. (There are very, very few mutations which alter how many eyes people have, because those are strongly selected against, but people do lose eyes to environmental causes, such as accident, disease, torture, etc.) The heritability of these numbers is about as close to zero as possible, but the genetic control of them is about as absolute as possible.

That text is actually a quote from here, and that article is even more interesting and explicit on this point.

Comment author: PhilGoetz 05 August 2009 03:37:42AM 0 points [-]

I don't need to read the linked-to article, as I've read other articles using the term "heritability".

Wikipedia says: "In genetics, Heritability is the proportion of phenotypic variation in a population that is attributable to genetic variation among individuals." It defines it as

heritability^2 = variance due to genes / variance in the population

Comment author: Jonathan_Graehl 05 August 2009 05:24:02AM *  0 points [-]

heritability : genetic control :: correlation : causation

Comment author: PhilGoetz 05 August 2009 05:41:05AM 1 point [-]

That's a partly-valid analogy, because things other than genetic control can cause high heritability measurements. But I don't think it's a strong analogy. You can't say, "Well, I might have the interpretation in the completely wrong direction here; the phenotypes might be controlling the genes."

Comment author: Jonathan_Graehl 05 August 2009 06:43:23PM *  0 points [-]

Heritability is unary. Correlation is binary (I'm talking about arity, not domain). You shouldn't "wrong direction" on a unary relation, but I guess that's just another reason I shouldn't have put that in the form of an analogy. I see that you're taking "heritability(trait) X" as "causes(gene-variance,trait-variance) X". That's definitely not what I intended.

I certainly wasn't trying to convince anyone of "heritability is nonsense!". According to Wikipedia, it seems that narrow-sense heritability, with gene-environment correlation removed, would be a direct indication of "genetic variation causes phenotypic variation" (within a framework of simple linear combination of each gene, and environment). I don't know how to tell if someone has actually obtained this number properly, though.

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