@Sturmwulfe
It also applies when a civilization has been at war for so long, that war-oriented ideals become commonplace thought and, again, diversity stagnates. World War II spawned some of the worlds literally greatest minds, but simply because the proper tech, and the proper inspirations were there. There will always be great minds, it's just disappointing to know not every great mind will be able to excel to his or her fullest potential <- without being ostracized.
For another example, take tradition. <-basically anything that's set to cause the effect of repetition, will systematically induce restricted cultural dynamics. I'm sure there's some research I can do find studies on the effects of bacteria exposed to different environments, and their ability to adjust and changes in behaviour. What an organism is used to causes it to maintain and stick to it's regular functions as tightly as possible. When it's environment
changes,
that's when the magic starts! This is true for both hostile and symbiotic environments.
And as I travel expeditiously across the interwebz, the more this hypothesis seems to be more like theory. It's evident, that somehow people treat difference with rejection moreso than with inquisition, and even with many who propose an inquisition do so with adamant sarcasm, usually towards the betterment of a joke or meme. This even runs deeply into corporations, esp larger corps which have less flexible policies <- however this is countered with addendum to policy, micro-regulating every relevant detail until you have not more than an inch of breathing space or else risk starting a nuclear chain reaction of policy violations!
This still only addresses the complacency of the population, and not the conformity. People are still lacking a good will to change for better, or worse, or at all. If millions of people agree that the iPhone is one of the greatest phones, despite how many actual phones are better, millions more will do their duty to buy an iPhone. The human market thrives on this principle, of which I attribute to some natural psychological flaw. I also think this 'exploiting' of our human flaws, by humans ever still, is slowly domesticating the population. People, namely in America, are more eager to conform to a standard than a) risk being wrong, and

risk being weird. They say nasty things on TV about weird people, say enough to host a theme on a TV talk show, Jerry Springer or Maury. Compared to the reapers, it's frighteningly similar.
They will not accept change, they will not negotiate, and they will do whatever it takes to prove their way is right. This sounds like the average human hearing a strange-but-new idea for the first time.