The evolution of democratic peace - out now in Nat. Comms.

Kingsley (first author) was a masters student under my supervision. Together, we set out to tackle a big question in evolutionary biology: why do some societies – human or otherwise – lean towards war while others stay peaceful? One long-standing idea, known as the “democratic peace” hypothesis, suggests democracies are less warlike than autocracies because lone rulers can launch fights for their own benefit, while democratic groups share the costs and gains of conflict.

But decision-making isn’t just a human affair. Many animal societies – from meerkats to fish shoals – also vary between leader-dominated and shared choices.

To test whether the democratic peace idea holds beyond people, we used evolutionary game theory, adapting the classic Hawk–Dove model so that whole groups, not just individuals, decided whether to fight or back down.

Their results show that the logic of democratic peace can arise without any uniquely human psychology: whenever more members have a say, groups are less likely to pick costly fights. This suggests a common evolutionary principle shaping how conflict and cooperation emerge across species.

The paper is published in Nature Communications https://www.nature.com/articles/s41467-024-50621-5