Gene-culture models and reductionism

In the random corners of Google, I was led to a short 2004 letter in American Anthropologist by Daniel Wildcat, Irena Sumi and Vine Deloria, Jr. I found this paragraph thought-provoking:

No doubt one can find high correlations between genes, languages, and kinship systems in many places. However, the de?nition of social structure that is associated with such analyses is terribly simplistic and rei?ed. Involving population genetics is particularly misleading: Population genetics employs a mathematical model whose crucial dynamic variable is mutation readable in genetic markers such as mtDNA and the Y-chromosome. The frequency of these mutations is matter of speculation: It is deemed accurate or credible when the computed spans of time between mutations ?t a preset, hypothetical scenario of a demic expansion. Exciting as such speculative science may be, it nevertheless yields bland, linear, and unimaginative speculation on humankinds past. Moreover, it seems to exploit the fact that few social scientists familiarize themselves with modern genetics, and likewise geneticists seem largely ignorant of what social scientists know about the way humans build their communities and imagine the past, as well as how social scientists in turn represent these notions. This mutual ignorance seems to increasingly produce unquestioned mutual belief (Wildcat et al. 2004:641).

This is at its root an anti-reductionist argument, and since I think there is substantial promise for reductionist approaches to culture history, I don’t subscribe to the motivating spirit of the remark.

But there is much here with which I do agree. Attempts at connecting genetic variation with linguistic or cultural history have been “bland, linear, and unimaginative.” They follow essentially nineteenth-century models of culture transmission, in which both culture and genes are inherited in a vertical direction, and horizontal transfer (of either) has little importance. Because selection has been assumed to be unimportant or insignificant, the genetic models must rely on bottlenecks and isolation to explain genetic differences. Cultural diffusion – and its extreme manifestation, language and subsistence shifts – are unwanted noise that only obscures efforts to reconstruct “deep history.” Correlations between genes and cultural traits are accidents of history.

I can’t say that the current pattern of biocultural research is wrong. People have developed clever ways to test the usual models, and those models will – after all – be correct in some cases. At worst, they will be rejected, and that increases our knowledge as well.

But there is much of interest that remains to be explained, that must involve different patterns of culture-gene interactions. Not just vertical transmission, but codiffusion, true coevolution of genes and culture traits, and historical constraints on both cultural and genetic changes. As we extend our data across the genome, we can study the interactions not of one or two genetic loci with culture history, but of thousands. Natural selection has been very common, not rare. This gives us an incredible opportunity to test hypotheses about the historical causes of genetic change.

These efforts may also be criticized as overly reductionist. But I find them very compelling because they make us focus on the role of individuals in culture-historical processes. In the usual models, individuals are passive repositories of genes and culture traits as they are passed forward through time. In models with genetic and cultural selection, individuals become agents, making decisions about adopting traits horizontally or vertically transmitted, and succeeding or failing based on both those decisions and combinations of selected genes.

References

Wildcat D, Sumi I, Deloria V, Jr. 2004. A response to Doug Jones. Am Anthropol 106:641.