Update: Sugden argues to augment game-theoretic explanations for the rise of social norms with the memetics of convention,
…[the] patterns of behavior [are not] necessarily efficient. They have evolved because they are more successful at replicating themselves than other patterns: if they can be said to have any purpose or function, it is simply replication. They do not serve any overarching social purpose; thus they cannot, in general, be justified in terms of any system of morality that sees society as having an overall objective or welfare function. The conventions that we follow may, however, have moral force for us. But if they do, that is because our moral beliefs are the products of the same process of evolution.