Ed Yong at Not Exactly Rocket Science has an excellent piece on using chess to explain the differences between men and women in the hard sciences. Turns out, participation not biology is key:
Every serious player has an objective rating - the Elo rating - that measures their skill based on their results against other players. Bilalic looked at a set of data encompassing all known German players - over 120,000 individuals, of whom 113,000 are men. He directly compared the top 100 players of either gender and used a mathematical model to work out the expected difference in their Elo ratings, given the size of the groups they belong to.
The model revealed that the greater proportion of male chess players accounts for a whopping 96% of the difference in ability between the two genders at the highest level of play. If more women took up chess, you'd see that difference close substantially.
I wrote about a study with a similar conclusion early this year.
Razib at Gene Expression writes a fascinating piece discussing the complexity of cousin marriage. Worldwide customs with respect to this vary widely as do the deleterious effects to possible offspring. He writes more in the Guardian:
A custom's ubiquity does not speak to its virtue. Because of the adoption of Greco-Roman monogamous norms by western Christianity, Europeans are among the cultures which have rejected polygamy. During periods of great inequality of power, even self-styled autocrats such as Henry VIII took only one wife at a time. It was this European society, where elite males were peculiarly constrained in their marital excesses, which eventually led the economic revolution which has so reduced inequality in income over the past two centuries.
Read the whole thing.