New research suggests that diet is responsible for our large brains

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A study published in the journal Nature Ecology & Evolution has found that foraging for fruit may be responsible for the evolution of big brains in primates. These findings challenge the long-held theory that primates and humans evolved large brains in order to deal with complex social interactions. A study published in 2012 claimed to prove that larger brain sizes can be driven by cooperation and teamwork. Scientists came to this conclusion by using computer models of artificial organisms with artificial brains.

These organisms competed in various games, and researchers showed that the transition to a cooperative society leads to the strongest selection for bigger brains. Authors said:


“Our model differs in that we exploit the use of theoretical experimental evolution combined with artificial neural networks to actually prove that yes, there is an actual cause-and-effect link between needing a large brain to compete against and cooperate with your social group mates.”


However, while cooperation can lead to big brains, this doesn’t mean that this kind of social behaviour was in fact responsible.

In this new study, researchers highlight that primates that eat fruit have around 25% more brain tissue than leaf-eaters with the same body weight. Co-author Alex DeCasien says that, “[fruit] is higher quality, it is more nutrient dense, it requires less digesting time, than the leaves.” Fruit-eating can provide more energy than leaf-eating, aiding brain growth.

But it’s not just eating fruit which leads to big brains, but foraging for it as well. After all, it takes brain power to find fruit, log its location, know how to get into the fruit and know when it’s ripe and ready to eat. DeCasien points out that this is much more demanding than eating leaves, which are present everywhere in the primate’s environment. She adds that a bigger brain may then allow for more complex social interactions.


Relevance to humans

Even though the study only looked at non-human primates, the results could also tell us a lot about why humans evolved to have such big brains. Chris Venditti, an evolutionary biologist at the University of Reading, underscores that we are the only primate that can get lots of calories from meat (because we cook it and so make it easily digestible). This extra energy in our evolutionary past could have given us more opportunities to grow larger brains. Previous research has suggested that eating meat and cooking food fuelled human brain evolution.



However, there are some issues with this new study. For example, researchers only looked at the relative brain size of different species. They didn’t analyse the size of the neocortex, which is involved in complex cognitive processes, such as perception, reasoning and thought. So it could be that the size of the neocortex is related to group size and social interaction. Robin Dunbar, who is a proponent of the theory that social interaction drives brain evolution, reminds us of previous studies linking the size of the neocortex and group size in humans and monkeys.


Other ideas about diet and human brain evolution

There are other hypotheses out there about how diet influenced the rapid evolution of the human brain (tripling in size in 7 million years; 1). A previous post on Red Planet Nutrition described how the omega-3 fatty acid DHA may have played a key role in increasing our brain size.

Dr Michael Crawford authored a paper which supports this notion (2). Crawford argues that the brains of our ancestors dramatically increased in size 6 million years ago because these hominids found supplies of fish (high in DHA). DHA is also an important constituent in our brain. We need it for proper brain function and health. However, other scientists have critiqued this hypothesis based on the existing literature (3).


Future evolution

We are, of course, still evolving. Although it’s not clear how are brains will evolve. It looks like our brains are shrinking rather than getting bigger (4). So increases in intelligence will most likely come from utilising the biological hardware that we have in the most effective way possible. This could involve designing and using better smart drugs and supplementing our minds with a computer interface. Soon it won’t be diet or complex social interaction determining increases in intelligence, but the extent to which we combine with computer intelligence.


About the author: Sam Woolfe @samwoolfe

I’m currently a Writer at The Canary, covering issues relating to the food industry, drugs, health, well-being and nutrition. I’m also a Blogger for Inspiring Interns, where I offer careers advice for graduates. If you have a story you want me to cover, drop me a message on Twitter (@samwoolfe). You can also check out my travel blog ( and personal blog ( to read my articles on philosophy, psychology, and more opinion-related content.





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