I've commented on height genetics now & then. It seems that the quantitative genetic supposition that variation on this trait was due to the cummulative effect of numerous loci of small effect is correct. Recent research has pinpointed about ~5% of the variance. In contrast, skin color variation is mostly due to polymorphism on about 6 loci; most of the variance is due to genes of large effect. This makes specific discussion of skin color easy, but height difficult.
I've been thinking about this when it comes social phenomena. Much of the verbal treatment presupposes a few large effect explanatory variables; but what if that's not correct? What if most social phenomena are contingent upon thousands of small effect predictors? How are you going to talk about this? And since we don't know the "gene" unit of social phenomena where do you even start? Of ourse quantitative social scientists focus on phenomena which do have independent variables of big effect; but most of the action might not be low hanging fruit, but rather dispersed in the canopy.
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The low-hanging fruit analogy isn't appropriate, since it's not as though social scientists are just running a social genome scan in the background while they surf YouTube, and then see which loci pop out as large effect sites. It takes real effort, insight, cleverness, etc. to see which variables matter.
But the larger point is well taken. However, if there has been recent, strong selection in the social genome to adapt humans to our new environments, we do expect to see a picture of a few large-effect sites and lots of harder-to-spot sites of small effect.
In the same way that loci causing skin color differences have been under strong recent selection for adaptive purposes, so have social loci affecting class structure. So it may be that there are just a few principal components that class breaks down into, such as time preference, IQ, and maybe work ethic / diligence.
Congratulations, you are now traveling backward on the road to serfdom. In just a short while you will arrive at Hayek's pregnant distinction between concrete economic knowledge -- the social/economic agents' dispersed knowledge of "time-and-place" -- and the theorist's concentrated knowledge of abstract principles emerging from social organization.
Hayek is gaining some long-overdue acknowledgment in economics, but the pomo sociologists have a long queue of appetizers to digest before they get anywhere near the dining room.
I tend to agree with this comment of Razib. Geneticists by the very nature of their profession tend to look for genetic causes of everything but it's quite self-evident that not is genetics, much less hardcore gentics (one gene > one phenotypical effect). That there are many other factors beginning by slippery epigenetics and ending by the very fact that we humans are very much genetically hardcoded not to be just genetically harcoded (i.e. we are very flexible and adaptative).
Is there a theoretical model that predicts why some traits are caused by many or a few genes - is it the age of the phenotype? I seem to recall Geoffrey Miller speculating in his Mating Mind book that if something was signaling genetic quality (e.g. creativity) then having lots of genes involved would be a more honest signal.
So it may be that there are just a few principal components that class breaks down into, such as time preference, IQ, and maybe work ethic / diligence.
i'm not talking about stuff that's heritable dude. or specifically, i'm not talking about micro/individual dynamics. i was wondering about macrosocial trends and the very general "explanations" that you see in history, international relations, etc.
Is there a theoretical model that predicts why some traits are caused by many or a few genes - is it the age of the phenotype?
precisely, you mean how the number variant genes which are implicated in the variation of a trait. generally, normally distributed traits which would often emerge from lots of loci are not strongly selected for; so it could be balancing selection of some sort. and yeah, i think age would matter insofar as perhaps variation has not bee exhausted because we're still on a transient.
OK, class and its components was a bad example, but what I'm saying still applies. The macrosocial things are changing rapidly, so a few big causes may underlie much of the variation across societies.
Society is like the weather; it emerges from the interaction of lots of rules; it's shaped both by history and chance. Look at complexity theory, complex adaptive systems, Santa Fe Institute, the work of Cosma Shalizi, etc.