countries with strong extended families as characterized by a high level of cousin marriages exhibit a weak rule of law and are more likely autocratic. ...Europeans became more individualistic, but I do not know if it is genetic or cultural.
These findings point to a causal effect of marriage patterns on the proper functioning of formal institutions and democracy. The study further suggests that the Churches’ marriage rules – by destroying extended kin-groups – led Europe on its special path of institutional and democratic development.
Human evolution is tricky to measure in modern times. John Hawks reports:
One of the most obvious cases of recent human evolution is the increasing frequency with which individuals don’t develop third molars, what is called “M3 agenesis”. This condition is when the third molars, or wisdom teeth, don’t form at all – the individual never developed them. ...So we do not know for sure whether this is evolution is action.
So M3 agenesis is a fascinating example of recent biological change in human populations, and we know very little about how and why it has changed.