Ashkenazi Jews

Ashkenazi Jews, the Jews of Central and Eastern Europe whose descendants settled in the Rhineland, are said to have the world's highest IQs for a particular ethnic group. This may be due to the long history of persecution of the Ashkenazi Jews and a result of natural selection to breed with someone intelligent.

This theory was proposed by Gregory Cochran and Henry Harpending in their 2006 report (PDF). They have a new book out called The 10,000 Year Explosion: How Civilization Accelerated Human Evolution.