"We have been evolving into a species that is super-cooperative: we work together with strangers, we can empathize with people, we are really an empathic flock," begins Carsten de Dreu, a professor at Leiden University. "And at the same time, there is increasing evidence from archaeological excavations all around the world that already 10, 20 and 30 thousand years ago, people were actually violently killing each other."

Trained as a social psychologist, de Dreu uses behavioral science, history, economics, archaeology, primatology and biology, among other disciplines to study the basis of conflict and cooperation among humans. In this Social Science Bites podcast, he discusses how conflict and violence – which he takes pains to note are not the same – mark our shared humanity and offers some suggestions on how our species might tamp down the violence.

"Violence," de Dreu explains to host David Edmonds, "is not the same as conflict – you can't have violence without conflict, but you can have conflict without violence." Conflict, he continues, is a situation, while violence is a behavior. Conflict, he says, likely always will be with us, but resorting to violence need not be.

The psychologist says behavior has a biological basis, and various hormones may 'support' violent actions. For example, greater concentrations of oxytocin – which helps maintain in-group bonds and has been dubbed "the love hormone" -- is found in primate poo after groups fights. But, he cautions, that is not to say we are innately violent.

But when we do get violent, it's worse when we're in groups. Then, the potential for violence, as he put it, "to get out of hand," increases, escalating faster and well beyond the violence seen between individuals (even if that one-on-one violence sometimes can be horrific).

"In an interpersonal fight, the only trigger is the antagonist. In intergroup violence, what we see is that people are sometimes blinded to the enemy – they might not even recognize who they were because they were so concerned with each other."

What drives this violence is both obvious and not, de Dreu suggests. "Even among my colleagues, there is sometimes fierce debate - conflicts sometimes about what are conflicts! But if you zoom out, there are two core things that groups fight about:" resources and ideas.

Fighting over resources is not unique to humans – groups of primates are known to battle over land or mates. But fighting over ideas is uniquely human. And unlike resource conflicts, which have the potential to be negotiated, "for these truth conflicts ... there is no middle ground, no trade-off." Regardless, he argues, values have value.

Citing recent work with colleagues, de Dreu says he thinks "these values, these truths, these worldviews that we have, that we share within our groups and our communities, within our countries sometimes, they are the 'oil' of the system. To work together so that we all can survive and prosper, we need certain rules, a certain shared view of how the world operates, what is good and bad, what is right and wrong. These are very important shared values we need to have in order to function as a complex social system."

But "when these values get questioned, or attacked, or debunked, that's threatening." Depending on how severe the threat is seen, violence is deployed. And sometimes, as even a casual observer may divine, it's not the direct quest for resources or to protect values that sparks violence, but what de Dreu terms "collateral damage" from leaders cynically weaponizing these drivers – or even inventing threats to them -- while actually pursuing their own goals.

But de Dreu ends the podcast on a (mostly) upbeat note. He says we can break the cycles of violence, even if there's no neat linear trajectory to do so, and concludes by offering some rays of hope.