[A. Pole]

There is also a vast body of research, both historical and sociological, that suggests democracy is the aftermath of a long slow evolution toward egalitarianism and economic liberalization. Ancient Greek democracy, for example, was an expansion on earlier consensual government.

It was not a long lasting experiment! In places not ready for this experiment we get things like in Ruanda or Weimar Republic.

[jb6]

Actually, if you look historically, no republic has lasted more then 300 years: not Athens, not Rome, not Thebes or the other greek states, not the Venitians, not Novograd, not Poland (before the partitions). None. All eventually devolved into bickering oligarches pretending to represent the people and eventually from amongst them or the disillusioned military, a dictator has always risen up. And these were the well established republics, there are plenty that folded up in no time at all. It's human nature.