by Patrick Appel

A reader writes:

I think Christopher Ryan leaves out part of the picture by suggesting that genetics can be the only source for evolutionary selection in the Darwinian sense.  This is basically an extension of the nature/nurture debate.  Just like the evolution of our genes can determine who we are and how we behave, so too can the evolution of cultural norms within a given society.  Societies that perpetuate ideas and norms that are beneficial to quality of life in the long run may prove more successful than societies that do not.  It's one part of the argument for why the west won the Cold War  -- capitalism proved to be a more successful idea than a state-controlled economy.  Thus, I would suggest that supposing (1) children from families that value and practice monogamy are more likely to be successful, and (2) such values perpetuate through generations, then this could indeed be a form of evolutionary selection.  Each successive generation from such families would have a higher likelihood of success than each successive generation from families that don't value monogamy.  Over many generational iterations, and all other factors being equal, one could predict the dominance of monogamous culture over others. 

Social evolutionary theory is a very real stream of social science, but it is obviously a much harder theory to pin down than genetic evolution because you don't have any code to point to as evidence.  I would recommend reading the groundbreaking works of Max Weber from a century ago and more recent work on evolutionary psychology by Steven Pinker, if anyone is interested. 

Another reader:

As far as genetic correlates of monogamy go, you might want to look at this study on voles...and related others. They seem to have identified a few genes that, when turned off, make a normally monogamous species polygamous. This is of course not an exact correlate to human behaviour--pair bonding in rodents is clearly not identical to human love and marriage--but it's about as good as we have right now.

I've seen the vole studies. Ed Yong had a good post on their significance a couple years back.

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