Cohabitation: Morality versus Evolution

In my experience the debate over cohabitation before marriage is dominated by this general debate

Con: Cohabitation before marriage leads to a higher rate of divorce (... for such and such a reason). Divorce, generally, is negative. Therefore cohabitation should be avoided.
Pro: Marriage is a big commitment. Cohabitation gives you a clearer vision of whether it will work out or not. Maybe cohabitation leads to more divorce for some people, but I will take my chances.

David Friedman's new blog has an interesting new take on this conundrum. His basic premise is that evolutionarily we become more emotionally attached to people with whom we have physical relationships. As such we may settle for a less than ideal mate today because the benefit of the relationship now seems to outweigh the uncertain future benefits if you go back on the market (and potentially don't find an equally good option). Because we "severely discount future benefits" cohabitation will lead to less searching and therefore a lower probability of finding of the ideal mate.

This is the kind of stuff I like to read. Unconventional approaches that lead to surprising conclusions.