It's definitely not obvious, given that many, many gregarious species may certainly have inter-group clashes and skirmishes at territory boundaries but no full-scale war. Animals in general avoid violence between conspecifics, for the obvious reason that it's rarely worth the risk of being hurt unless you're very sure you're going to win. Dying for your group is something you almost never see outside eusocial species. Never mind dying in your prime reproductive age!

Normally there are more than 2 actors, which changes the reward structure.

X spends resources to kill Y. This benefits X because X doesn’t have to compete with Y anymore.

However Z also gets the benefits because they don’t have to compete with Y either. In addition Z hasn’t spent any resources to eliminate Y so Z wins. The stable equilibrium is 100% strategy Z.

Most animals will use violence in self defence, or when fighting over a specific resource. They don’t kill to remove competition.

Chimps and humans are an exception to this. Likely it’s because the coalitional nature of human and chimp violence reduces the cost of inflicting the violence to near zero, and the costs are spread across the group, so it’s worth doing.

> When competing for resources, killing your neighbour frees up resources, which you can take. Most species of animal and even plants do this to some extent.

If anything, I'd say plants do it more. Everything in the garden is trying to kill everything else.

Yes, but war is worse for all parties generally.

Lions murdering prey to eat is a stable equilibrium.

Primates fighting each other is not.

Murdering for acquisition of a resource is short term advantage.

We are strongly, strongly evolutionary oriented away from 'murder' - it's the original sin. It's not something we even argue over. Murder = Bad. No disagreement across cultures. Murder = social cheating. No disagreement there either.

Or put another way - the 'self' can gain advantage with murder, but the group and species probably will pay for it long term.

I wonder if there are just things that species really have to learn over and over, particularly things like 'active deconfliction' etc..

There's a simple energy argument for both predation and war. It is energetically cheaper to take than to build. If you can take with low risk, there is no (energetic) reason to not do so.

Collaboration is the exception. That collaboration is everywhere in many forms is a testament to the power of natural selection.

Important to remember that we as humans no longer compete for resources.

We have more than enough resources to go around for 10 billion people.

The limiting factor is in intelligence and dexterity. In other words, we get richer when we are more.

orangutans deal with similar and are notorious for being peaceful

Except in this instance the conflict erupted after the population size was reduced due to disease so it's not entirely clear this was caused by the scarcity of resources. Nor is it clear what selective advantage mutually destructive wars would have assuming plenty of resources. The researchers posit group relational dynamics being the primary factor.

> When competing for resources, killing your neighbour frees up resources, which you can take

I don't think it's that straightforward. War is usually extremely wasteful for all involved, even the victor. Plus it puts the whole group at risk, if it spirals out of control.

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