A cursory glance back through human history should be enough to convince anybody that our species is in love with hate.
In the opinion of anthropologist R. Brian Ferguson, this doesn't mean we have good reason to think large scale social conflict is in our genes.
War isn't in our nature, he argues. But that doesn't mean there's an easy way to avoid it.
For as long as humans have recorded their achievements in paint and stone, war has been a familiar story. So we could almost be forgiven for thinking it's a fundamental part of being human.
Just how ingrained is large scale social violence, though? To borrow a metaphor, are humans innately war-mongering hawks looking for a fight, or peace-loving doves driven to take up arms?
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"There is definitely controversy in the field when it comes to this question," says Ferguson, who is the author of a recent article pushing back against hawkish assumptions.
"But it is the overall circumstances that we live in that creates the impulse to go or not go to war."
Sure, we have a constant tide of media reporting the latest causalities of bombs and bullets. Not to mention historical accounts of our thirst for battle, and even cave paintings seeming to show figures running one another through with spears.
But it's hard to know how much of our storytelling demonstrates a fundamental violent streak, and how much is a reflection of our fear and desire to record it.
That's even assuming early depictions of armed skirmishes are all they appear.
"Other scientists point out that some of the incomplete figures in those cave paintings have tails, and they argue that the bent or wavy lines that intersect with them more likely represent forces of shamanic power, not spears," Ferguson contested in a Scientific American feature.
Even if our own accounts are biased, surely the archaeological record itself isn't … right? A species that evolved to violently drive out competing populations should leave behind some solid evidence of its aggression stretching back beyond antiquity.
Advocates of the hawk model of innate human aggression point out the high percentage of deaths due to warfare throughout history.
"Twenty-five percent of deaths due to warfare may be a conservative estimate," anthropologists Steven LeBlanc and Katherine Register claim in their book, Constant Battles.
If more than a quarter of all humans died as a direct result of some kind of group violence, it would be reasonable to expect to have some sort of influence on how we've evolved.
But Ferguson disputes such figures, accusing their authors of cherry picking, pointing out that signs of a violent end aren't necessarily a signature of battle.
"Individual killing is not the same as war on social groups," says Ferguson, conceding homicide might have a rather common threat.
"War leaves physical traces that archaeologists can find. When and where it began is very different in different places around the world, but there are stretches of even thousands of years when there are no clear signs of war."
This ambiguity on how to interpret primary evidence – from signs of skeletal damage to alleged weapons to the role of buildings as defensive structures – means evidence in favour of the hawk argument is too weak to be conclusive.
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If humans are inclined to be peaceful, why fight at all?
As a researcher of contemporary conflicts such as Vietnam and Afghanistan, Ferguson puts his money on warfare as the exception to the rule, arising out of unusual conditions that have been absent for most of our past.
We unite against each other in violence not because we're driven by genes, but because we've found ourselves living in sedentary, hierarchical communities defined by boundaries that risk limiting our resources.
That's not to say in a world where every need is met, and everybody shares a sense of power, violence of all flavours would be absent.
Harvard psychologist Stephen Pinker argues much the same in his 2011 book, Better Angels of Our Nature, when he says, "The point is not that we have entered an Age of Aquarius in which every last earthling has been pacified forever. It is that substantial reductions in violence have taken place, and it is important to understand them."
Like Pinker's book, Ferguson's argument won't be the final word on the matter. New evidence and fresh perspectives will continue to refine the case for when and where humans turn nasty.
But if some resemblance of world peace is even a remote possibility, it would be nice to know we're not also fighting our own basic nature in achieving it.
