They have not, yet.
I see natural selection as usually a situation of degrees. For example, women prefer to select a mate that reflects “what they (think they) want” in a husband and father. The same way, males choose women as mates. Over time, this results in more males and females of the preferred type.
Likewise, when a more efficient way of doing things, such as civilization, comes along, more primitive and barbaric ways in proximity to civilization are doomed to die out, as efficiency is recognized even by primitive people as “better”.
This is actually the biggest selling point of democracy and republican democracy. Because even illiterate and uneducated farmers can see the common sense advantages of such decision making over even informed dictatorial management. And it is easy to figure out that while democracy works at the lowest level, it is far more efficient to subcontract representation at higher levels in most cases; thus republicanism is born.
Freedom and liberty are just necessary side effects to this efficiency. Democracy and republican democracy just work better with freedom and liberty.
Importantly, when the idea of efficiency is introduced to democracy and republican democracy, the idea spreads like a virus. From peasant to king, anyone can “catch” it, without overt symptoms. But from that point they not only spread it, but facilitate its growth.
It is the natural selection of ideas.