For the past several decades, scientists have been fascinated by the "social brain theory" — the idea that certain animals evolved big, powerful brains to cope with the complexities of social life. A new computer simulation has now shown that this assertion is likely correct.

Our bulbous brains require a lot of energy to function. Like, a lot of energy. That one organ alone requires 25% of our body's total fuel stores. So from an energy allocation perspective — and thus from an evolutionary perspective — it sure as hell better be worth it.


Coordination Is Good

Other animals haven’t had to make these sorts of Darwinian adjustments. Herd animals and insect swarms, while social, take on loose social arrangements that are typically based on short-term advantages.

But other animals, like primates, whales, dolphins, and elephants, have social lives that are far more dynamic, often involving intense coordination with multiple group members. And it’s no coincidence, say some scientists, that these animals have powerful and complex cognitive capacities.


And indeed, the social brain theory suggests that brain size affects the speed, volume, and sophistication of decisions that can be made amongst interacting individuals.

For pre-civilization humans, these decisions and coordination abilities yielded considerable functional advantages — advantages that trumped free-riding and other not-so-social behaviors. For example, coordination allowed early humans to agree on the direction of travel to a desirable resource, to defend against predators or rival groups, or any other ecologically important behavior that required group members to synchronize or coordinate their behavior.

It also allowed them to accept a set of cultural or moral values that served as a cue, or ‘tag’, of trustworthiness and willingness to reciprocate. The ability to communicate through language, therefore, would seem to be an important part of the overall equation.


Simulating Social Interactions

This thesis, that large social groups are only possible with powerful brains, was recently affirmed by an Oxford University team led by Tamas David-Barrett.

By using agent-based modelling, they were able to challenge their simulants by giving them coordination problems that required behavioral synchrony. Each agent had to do their part at the right time and in just the right way for the group to be able to act as one. And what they found was that the viability of group size increased as calculation (or cognitive) capacity increased.


What’s more, the simulations also showed that, in order to achieve a significant further increase in group size, the simulants had to switch to a more complex information processing strategy that allowed them to differentiate among their problems.

In other words, they had to develop the capacity for complex language.

“By permitting third party information to be exchanged, it allows the group to cut through the glass ceiling... and significantly raises the limit on group size,” noted the authors in the study, which now appears in Proceedings of the Royal Society B.


Thus, the evolution of cognitive and communicative complexity is driven by the environmental demand for large social groups — but it’s only when there’s a need for large groups that the selection pressure will be strong enough to justify the resources costs (energy, time, etc.) involved.

You can read the entire study at Proceedings of the Royal Society B: “Processing power limits social group size: Computational evidence for the cognitive costs of sociality.”

Image: Pichugin Dmitry/Shutterstock.