If you were to make a rule in your company that prohibited the hiring of left-handed people, over time your firm would have only righties. Sure, a few lefties would try to pass themselves off as righties and work to undermine the rule, but if you were vigilant the left-handed would be eliminated from the company. The reason for this is over time, it would become part of the culture. The left-handed, even those posing as the right-handed, would eventually be detected and removed.
This may sound a bit weird, but company culture is a real thing and these sorts of rules have been done in the past. Airlines used to hire only women as stewardesses, and they had size requirements. The women had to fit the uniform size range. This was a signal that they wanted petite, pretty girls for the job. Not only did this rule eliminate the big girls, but it also eliminated the homely. The uniform requirement and associated marketing sent a signal to the homely girls that they were not welcome.
This sort of selection works in human societies as well. If for some reason a society decided that left-handed people were dangerous or degenerate, over time the left-handed would become very rare. The lefties would have fewer mating prospects, so fewer of them would reproduce. We know this is true, because northern Europeans have a variety of eye colors. Unusual eye color became a mark of beauty, especially in women, so the result was a proliferation of eye colors.
Of course, people do not sit around thinking, “How can we create a set of cultural rules in order to eliminate the left-handed?” Cultural rules just sort of happen. They evolve through experience and the changes they create in the people. It is a dynamic that can only be understood from a distance, the distance of time. People in northern Europe did not notice the changing standards of beauty that rewarded bright eyes, light skin and light hair. They just noticed the cute blond girl in the next hut.
This is something to consider in the political realm. Different political and cultural systems select for and against different things. The Janteloven in the Nordic countries is a set of informal rules of conduct. The result is a political economy that strikes most Americans as boring in the academic socialist sort of way. Generations of selecting for people inherently humble and eager for comprise means their politic-economy reflects the nature of the dominant type on these societies.
In America we see the opposite. Democracy will always select for the flamboyant and dramatic, because the coin of the realm is persuasion. You cannot persuade people unless they notice you, so getting noticed is the top priority. This was true on Ancient Athens, where persuasion and flamboyance became precious qualities. The sophists went around promising to teach young men of wealth how to be gifted orators, which meant being able to hold a crowd and make compelling arguments.
Of course, there are many ways to get the attention of the people. Until fairly recent in America, this meant doing something important. Generals used to make good presidents, because they had done attention getting deeds and been trained in how to speak to men in order to convince them of the cause. Successful lawyers were always good at politics, because they are selected for their ability to persuade. Into the 20th century, America was largely ruled by lawyers and generals.