When you have a great king, it's among the best forms of government. The problem is that that great king's successor is probably not also great, and under a bad ruler, it's among the worst forms of government, and that bad king can last for your entire lifetime.
It's never spectacularly efficient, but the US' form of democracy is meant to be much lower variance. I think it's a good tradeoff.
Not sure if I would agree, given that estimates suggest that homo sapiens had evolved approx 400k years ago, and most of recorded history (with the somewhat stable hierarchies) lasts, at most, 20k years. So potentially much of recorded history, but certainly not proven to be necessary for evolution.
It's never spectacularly efficient, but the US' form of democracy is meant to be much lower variance. I think it's a good tradeoff.