There was a period of time when I devoured the works of Richard Dawkins, which inspired me to read in related areas like primatology. I discovered a lot of insights into human nature by learning about our heritage from our primate ancestors and by comparison with our primate cousins.
Among the things I learned about general evolution is that random mutation provides the raw material on which selection operates to power evolution. Traits that are contrasurvival are weeded out; positive traits are selected and thrive; and it's possible for neutral traits to survive if they're truly neutral, taking into account the "energy cost" to build an unneeded organ or to engage in a nonproductive behavior.
Given that, I would have to assume that primate social structures have positive survival value unless proven otherwise. Makes sense: Mutual protection against predators and rivals, and simple division of labor--primate tribes divide into simple role categories like females gathering food and beta males standing watch. Adam Smith only traced the development of markets and division of labor back a few thousand years; if he'd read Dawkins he'd have gone back several million years.
The really interesting thing is the supposition that advanced social structures promoted the development of intelligence. Being a member of a tribe requires additional mental effort to keep track of the location and identity of fellow tribesmen, the relationships of other members of the tribe as well as your own, the conventions and rules of the tribe, and so on. But perhaps what's most important of all is that a social order requires communication, and I think that the facility for communication is the one trait whose ramifications for intelligence snowballs as the species evolves. It's a multiplier.
Obviously, intelligence is a very useful trait, and we manage to survive in spite of spending most of our existence trying to get to the top of the heap and squash the others down. But this might explain much of our violent history.
So, you see, I'd say that we didn't survive in spite of living in a social hierarchy, but largely because of it. That instinct to "get to the top of the heap and squash the others down" is why humans are rare in the animal kingdom for our enthusiasm for killing members of our own species. We gained a lot from primate social structures, but we paid a heavy price for it.
The relevance of all this noodling is the question of whether we can ever evolve beyond our primate heritage, or whether we'll be forever constrained by it. Because of our intelligence and social natures, for many millenia now our evolution has taken place in the abstract sphere of our societies and our collective knowledge and expertise, rather than our bodies. As far as we've gotten so far is mostly an incredibly elaborated version of the simple primate tribe.
Say what you will about the results, everyone who's theorized about an alternative social order and tried to implement it has been an active participant in our continued evolution. Evolution requires experimentation in order to have raw material from which to select the winners and discard the failures. Hamilton and Jefferson and Marx and Rand and all the rest are necessary agents of social mutation.
I've said before that while I do value a degree of conservative thought in our society for caution and balance, it would be a disaster if conservatism ever won completely. I would also observe that any new ideology, however radical it seems at the time, becomes conservative when it succeeds and shifts gears to preserve itself. Conservatism (in that broad sense) values tradition and fiercely resists further experimentation. The conservative ideal is a static state (condition) in which (abstract) evolution ceases or is at least vigorously discouraged. If you think you've already achieved perfection, you can never advance further.
I don't mean to pick an ideological fight about conservatism in the narrow political sense, just to suggest stepping back and placing our fleeting ideological battles in the larger context of human evolution. The conservative defends what's been proven to work; the liberal proposes trying something new that might, or might not, work even better. We need both, conservatism to consolidate our gains, and liberalism to advance further.
We're participating in evolution right here and now at the tense interface between those diametrically-opposed forces.