Animals in general always tend towards two binary opposite behaviours, each of which is more successful in certain enviroments. It's a sort of hedging of the be

Animals in general always tend towards two binary opposite behaviours, each of which is more successful in certain enviroments. It's a sort of hedging of the bets, in case unexpected situations spring up. As such, there will always be extremes of both behaviours - the bird that takes more risk to get the worm, and the other bird that takes less risk. Depending on the external situation, one of the two types will always dominate. It's my belief that the concentration of genetic tendencies is what is causing the increase - people from universities tend to marry people from universities, and so there is a similarity in tendency among people who are reproducing, and so there is a larger tendencies for the extremes to manifest themselves. It's like the sickle cell gene - when the population is diverse, this gene hardly shows up as a disease, but when the community is closed, the disease comes up very often.