It does. Read The Bell Curve. These days due to improvements in transportation like the highway system, cars, planes, etc., it's ever more the case that smart people find themselves working, socializing, and having families with smart people. The opposite of this is also true. It's ever more the case that dumb people find themselves working, socializing, and having families with dumb people. Richard Herrnstein and Charles Murray call this social stratification. Intelligence is extremely highly influenced by genetics and therefore, since it's increasingly the case that dumb people are mating with dumb people and smart people are mating with smart people, it's likely that people are getting dumber and smarter than ever before. There will be a much starker difference between the elite and the downtrodden in the decades to come.