It has to be some combination of both

There is a debate in biology as to whether evolution is primarily driven at the gene level (Dawkins), the individual (Darwin) or at the group level (Wynne-Edwards). The debate ebbs and flows over time. While much of the discussion is couched in either-or terms, I think the reality is that evolutionary forces act at all three levels but with varying intensity based on ill-perceived contextual circumstances. As I said earlier, the Human System is multivariate, complex, chaotic, non-linear, homeostatic, self-correcting, contextually sensitive, dynamic, heterogeneous and ridden with tipping points and hidden feedback loops. This is true in biology and it is true in other fields such as economics, politics, etc.

There is a corresponding debate about the sources of human economic differences. Some wish to make the argument that one’s position in life is simply a matter of “luck”. While exogenous shocks are a matter of routine, it is clear that shocks on their own do not determine outcomes. It is the response of individuals (and groups) which determine the consequences of shocks. Some economists/sociologists/political theorists posit that differences in individual and group outcomes is driven primarily by geography (Diamond), history (Landes), culture (Huffington and McCloskey), social institutions (Acemoglu and Robinson), national IQ (Lynn and Vanhanen), human capital development (Lucas), rule of law and property rights (DeSoto) or values and behaviors (Heckman and Murray). Just as with the case of biological evolution, the argument is usually cast in either-or terms (with usually some sort of mild concession that it is more complicated than that, a concession then obviated by the binary arguments then made) but the reality is almost certainly that all of those elements are consequential at different times and under different contexts. It is also probably true that there is some sort of hierarchy of potential impact. My personal guess would be that the hierarchy might be culture, history, rule of law, institutions, values and behaviors, geography, human capital development, and finally national IQ (and I suspect that national IQ is not only a red herring but also simply incorrect).

I mention this because of an interesting blog post on the emerging implications of the field of epigenetics by Timothy Taylor, Fetal Origins and Epigenetics: Interview with Janet Currie.

One of the things I talked about in my Ely lecture was what mechanism might underlie the long term effects, and I raised the idea of “epigenetic” changes as one possibility. The way I like to think about that is you have the gene, which only changes very slowly when you have mutations. But then kind of on top of the gene you have the epigenome, which determines which parts of the gene are expressed. And that can change within one generation. There are animal experiments that do things like change the diet of guinea pigs and all the baby guinea pigs come out a different color. It can be pretty dramatic. ... The idea is that the fetal period might be particularly important because these epigenetic switches are being set one way or another. And then once they’re set, it’s more difficult to change them later on.

I think we haven’t really been able to look at all of the implications of that given the limitations of the data. We don’t have very much data where we can follow people from, say, in utero to some later period. But, that’s where the frontier is, trying to do that kind of research and make those linkages....

I think a really interesting thing about the fetal origins hypothesis for public policy is that if it’s really important what happens to the fetus, and some people think that maybe the first trimester is the most important or the most vulnerable period, then you’re talking about women who might not even know that they’re pregnant. It really means you should be targeting a whole different population than, say, 15 years ago, when we thought, oh, we need to be targeting preschool kids instead of kids once they reach school age. Now we’re kind of pushing it back. Then it was, “We need to be playing Mozart to infants.” Now the implication is that we’ve got to reach these mothers before they even get pregnant if we really want to improve conditions.

Epigenetics implies that it does not make sense to talk about nature versus nurture. If nature is the gene and nurture is the thing that sets the switches, then the outcome depends on both of those things. So you can’t really talk about nature or nurture in most situations. It has to be some combination of both.

This ties together both the idea of evolution (genes) and development (epigenetics).