Kaj_Sotala 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: Kaj_Sotala 05 August 2009 12:58:45PM 2 points [-]

Note that McArdle responds in the comments:

Reread the post. I did not say that environment wasn't interacting with genes--indeed, that was the entire purpose of the height comparison. I was responding to people who claim that individual outcomes can't be rooted in genetics because after all, there were no fat people in Auschwitz, plus we're all getting fatter. I understand heritability quite well, thanks--or at least, I already knew everything you wrote before you wrote it, and nothing in my post contradicts it.

(Not saying anything about whether her defence is right or wrong, just pointing it out.)

Comment author: Jonathan_Graehl 06 August 2009 01:21:44AM *  0 points [-]

Interesting. I don't believe her. I think her purpose was to suggest that weight is nearly as immutable under changes in diet and exercise as height.

Well, average height is also increasing in the population. Does that mean that you could be as tall as me, if you weren't too lazy to grow?

Twin studies and adoptive studies show that the overwhelming determinant of your weight is not your willpower; it's your genes. The heritability of weight is between .75 and .85. The heritability of height is between .9 and .95.

On the other hand, I do think there's far more to appetite and obesity than willpower[1].

Are there people with genetics such that, had they been given a diabetes+obesity inducing diet as children, they would still be rail thin and fidgety, burning tons of calories without explicit exercise? I think there are.

But I expect interaction between environment and genes to be very high in obesity[2], so heritability can't be used on its own to draw that conclusion.

[1] "studies of monozygotic and dizygotic twins have unambiguously shown that there is a much greater resemblance in the degree of obesity between genetically identical monozygotic twins" - http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1119832 - this is evidence for genetic variation in obesity with nearly constant environmental factors (clearly the availability of calories is a prerequisite for obesity).

[2] Extensive fictional evidence exists in the rotund mother who tries to fatten up her offspring when they return for the holidays: "put some meat on your bones!". Seriously,

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