Judging other people let us grow our large brains

Scientists have long been working towards understanding what drove the rapid evolution of the human brain over the past two million years, and now, a team of computer scientists out of Cardiff University have a new suggestion: Our brains grew through sizing up other people.

To put it less simply, judging whether someone else is worth helping led to our relatively large brain size.

“Our results suggest that the evolution of cooperation, which is key to a prosperous society, is intrinsically linked to the idea of social comparison — constantly sizing each up and making decisions as to whether we want to help them or not,” explained Professor Roger Whitaker, from Cardiff University’s School of Computer Science and Informatics, in a press release.

“We’ve shown that over time, evolution favors strategies to help those who are at least as successful as themselves.”

Learning About Ourselves Through Simulations

According to their study, which can be found in Scientific Reports, the team came to these conclusions after running hundreds of thousands of computer simulations based around a theory known as social brain hypothesis.

“According to the social brain hypothesis, the disproportionately large brain size in humans exists as a consequence of humans evolving in large and complex social groups,” said researcher Professor Robin Dunbar.

The research team took this idea a bit further by proposing that the behavior necessary for such groups itself—like cooperation—drove the evolution of the human brain. Specifically, they hypothesized that the constant assessment of other humans and judging whether or not to help them altered the human brain over the generations until it reached its current form.

To test this idea, the team created a sort of game using computer models. In this game, two simulated players were randomly chosen from the population. One player would then make a decision regarding whether or not they wanted to donate to the second player—a decision based off of how the first player judged the second’s reputation.

If the first player decided to donate to the second, they incurred a cost and the second player received a benefit. Both players’ reputations were updated, and a new game began. This was repeated hundreds of thousands of times.

The results seem to certainly favor social brain hypothesis.

“Our new research reinforces this hypothesis and offers an insight into the way cooperation and reward may have been instrumental in driving brain evolution, suggesting that the challenge of assessing others could have contributed to the large brain size in humans,” said Dunbar.

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Image credit: Thinkstock

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