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.
Okay, I’m reading the article now. I am no expert in this area, but it seems to just be wrong.
First, it is patently false that “heritability says nothing about how much the over-all level of the trait is under genetic control.” Heritability is defined in a way that is designed to tell you how much of the trait is under genetic control. That’s its purpose. It’s not a perfect measure, but it’s wrong to say that it tells you nothing about what it’s designed to tell you something about.
I expect the textbook example of heritability of number of arms being misleading is a textbook example of when heritability measurements go wrong, not a textbook example of what heritability is supposed to measure.
The author’s argument is that heritability is variance associated with different genotypes over total variance; all members of the population have different genes; therefore, everything has 100% heritability. Furthermore, the author goes on to say, there are interactions between genetics and environment, and other factors that are correlated with genetics, and so your heritability measurement isn’t meaningful anyway.
This is wrong, for several reasons:
It would require psychologists to sequence the DNA of their subjects.
If it were correct, psychologists would eventually notice that everything had 100% heritability.
Psychologists design experiments measuring heritability so that some pairs in the population share more genes than other pairs.
Psychologists design experiments to try to control for those other factors correlated with genetics. If they don’t, that’s a design flaw.
I don’t think the author is really saying that people are misunderstanding the technical definition of ‘heritability’. He is saying that all of the studies of IQ have been poorly designed, and so didn’t measure actual heritability.
The web page linked to seems to be politically-motivated, to show that IQ is not genetic. I also note that I read half of the book he refers to, which was written in response to The Bell Curve, and as science it was a lousy book. My recollection is that it was long on moralizing and attempts to create associations between The Bell Curve and Bad Things; but was not good at finding errors in the book it condemned so vigorously. It was also motivated by the same politics. It reminded me of what Einstein said when 30 Nazi scientists wrote a book against Relativity: “If they had been right, it would have taken only one scientist.”
Godwin’s Law! I win!
I think I can even call “large group of eminent scientists write a politically-motivated but scientifically weak book refuting another book” a trope, since the same thing happened with the “Against Sociobiology” letter of Gould etc.
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
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.”
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.
Have you actually read the linked-to article? Heritability != genetic control. The textbook example:
That text is actually a quote from here, and that article is even more interesting and explicit on this point.
Okay, I’m reading the article now. I am no expert in this area, but it seems to just be wrong.
First, it is patently false that “heritability says nothing about how much the over-all level of the trait is under genetic control.” Heritability is defined in a way that is designed to tell you how much of the trait is under genetic control. That’s its purpose. It’s not a perfect measure, but it’s wrong to say that it tells you nothing about what it’s designed to tell you something about.
I expect the textbook example of heritability of number of arms being misleading is a textbook example of when heritability measurements go wrong, not a textbook example of what heritability is supposed to measure.
The author’s argument is that heritability is variance associated with different genotypes over total variance; all members of the population have different genes; therefore, everything has 100% heritability. Furthermore, the author goes on to say, there are interactions between genetics and environment, and other factors that are correlated with genetics, and so your heritability measurement isn’t meaningful anyway.
This is wrong, for several reasons:
It would require psychologists to sequence the DNA of their subjects.
If it were correct, psychologists would eventually notice that everything had 100% heritability.
Psychologists design experiments measuring heritability so that some pairs in the population share more genes than other pairs.
Psychologists design experiments to try to control for those other factors correlated with genetics. If they don’t, that’s a design flaw.
I don’t think the author is really saying that people are misunderstanding the technical definition of ‘heritability’. He is saying that all of the studies of IQ have been poorly designed, and so didn’t measure actual heritability.
The web page linked to seems to be politically-motivated, to show that IQ is not genetic. I also note that I read half of the book he refers to, which was written in response to The Bell Curve, and as science it was a lousy book. My recollection is that it was long on moralizing and attempts to create associations between The Bell Curve and Bad Things; but was not good at finding errors in the book it condemned so vigorously. It was also motivated by the same politics. It reminded me of what Einstein said when 30 Nazi scientists wrote a book against Relativity: “If they had been right, it would have taken only one scientist.”
Godwin’s Law! I win!
I think I can even call “large group of eminent scientists write a politically-motivated but scientifically weak book refuting another book” a trope, since the same thing happened with the “Against Sociobiology” letter of Gould etc.
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
heritability : genetic control :: correlation : causation
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.”
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.