are we basically more like banobos or chimpanzees?
And I have no idea. The way we have thought about this problem from the Enlightenment forward tends to go something like this:
Without some kind of coercion would we get along okay or would life be more like Lord of the Flies? Hobbes, Freud, Bataille, Nietzsche, ... : state of war of all against all (more or less). Rousseau, Bakunin, Kropotkin, Marx (ish), … : we more or less get along (after some troubles, sometimes).
Answering this question maybe doesn't matter over much. We can become different no matter what. But it does seem to matter in one respect. If we are basically bad, then fascism is good. If we are good, then fascism is bad. See what I mean? If we are more like chimpanzees, prone to fighting and killing and domination then something like the king or state or ideology must step in to protect us from ourselves. If instead we are more like bonobos, prone to play and rampant fucking and cooperation, then what we need is to liberate our humanity from the coercion and demands of the repressive king, state, ideology...
Nineteenth Century anarchists believed in our humane human nature so thoroughly they were willing to murder in order to bring down the state and free the basic goodness longing to come out of everyone. Sans-culottes, Decembrists, Bolsheviks, Communards … all felt some similar kind of optimism. Our moment in history was the problem. Not our humanity.
Perhaps our humanity is only this very thing then: Robespierre erecting the guillotine. This reminds me of the famous Stanley Milgram experiments, where most of us seem willing to torture another human, sometimes to death, in the service of a greater good, or a higher authority.
(Here's a great TED talk about Bonobos. Ironically this "make love not war" cousin of ours is being hunted to extinction, by us).