Humanity’s primary selective advantage is not intelligence, but our social structure and intellectual *variance*. Every individual does not replicate every other individual’s discoveries; rather, one unusually bright person discovers something novel and shares it, enabling everyone else to benefit as well. This is part of our evolutionary heritage.
This explains a huge amount of human behavior which appears irrational under the assumption that intelligence is humanity’s primary selective mechanism. This is both why people tend to have an altruistic streak and why stupidity still exists. It is why tradition still exists, and thus why religion was naturally selected for and culture evolves. It is why war is made on a *group* rather than individuals – it is why genocide is practiced. It is why capitalism works (it provides an individual incentive to further foster this behavior). It is why the masses behave not like sheep, but like dogs, and why a very large number of people can be persuaded by individual demagogues and movements.