On Sun, 8 Jul 2007, Dwayne Monroe wrote:
> > So why, if corpulence is so baked in the cake, are Americans now so >
> > much fatter than they used to be, and so much fatter than most other >
> > people in the world?
>
> Do we really know this to be true?
>
> Of course, current stats say this is so but as Jerry (citing Gina Kolata)
> points out, we only have figures for the post WWII period
Yes, but within those figures there is a drastic change starting 25 years ago. If you want to say that the huge weight gain since then is purely a range change, you've basically assumed what you want to prove. And you haven't explained the change we want to explain at all.
AFAICT, the genetic inference is simply that -- the inference any biologist would make based on the what seems to be invariant behavior (namely that most people who try to diet fail). But the "n is tiny" argument that you make above about the stats is much more of an objection to a biological argument that it is to a social one. There is zero justification to consider diet failure a biological invariant if all you have is data on one population in one time period -- it doesn't matter how many people are in that population.
Despite this, genetic determinism is the near universal inference of choice among biologists anyway. But that doesn't seem mysterious. This is biology's null-case hypothesis, the one biologists tend to assume until they disprove it. It's what guides their research. If they assumed a social hypothesis, they'd be out of a job as researchers -- they have no competence to investigate that. (Sociologists FWIW exhibit exactly the same behavior in reverse and for the same reasons. They assume all widespread and seemingly intractable behaviors must be caused socially, and will continue to assume it until disproven. Which disproof, in both cases, is usually impossible, to both of their relief.)
Lastly, but perhaps most importantly, I would think by now that everyone had given up the whole genetic/environmental opposition. Genetics operates by making us more or less sensitive to environmental stimulus (using environment here to cover every realm from the micro-cellular to the macro-ecological). It does not stop us from being influenced by the environment. Including the social environment, which is one of the most important. Including in a long term, one way direction, like getting fatter. (Or taller). And it doesn't at all proscribe what can be done by willpower. It only determines what is easier and what is harder -- and part of how much.
Michael