It’s often said that ‘you are what you eat’. As proof of the truth of that old adage [Ed. – Careful. Surely it’s, at best, evidence in support of that assertion..?], Mr Cuttings can reveal why we humans are so jolly clever. It’s because we have big brains (!) And that’s because a long, long time ago our ancestors chose to eat fruit.
So, what’s the real story behind this ‘revelation’? Investigating brain size in >140 non-human primates (species such as monkeys, apes, and lemurs), Alex DeCasien et al. concluded that there was no link with brain size and the animals’ sociality (‘the action on the part of individuals of associating together in communities’), but there was with their diet. In particular, they found that fruit-eating primates – frugivores – have approx. 25% more brain tissue than generalist plant-eating species. So, it’s not just about eating plants, but consuming the right part of a plant.
The suggestion is that fruits give their consumers a diet consisting of energy-rich components that are more accessible than they are in other plant parts such as leaves. Consequently, those other sources require much more work to get the lower amount of energy from their tougher cells and tissues, and therefore don’t deliver the brain-boosting calories of fruits.
Others argue that this study does not necessarily preclude social interactions as another evolutionary driving force behind the development of bigger brains (such as vegetarians claiming superiority over non-vegetarians, is there now a pecking order amongst those on various plant-based diets? Are fruitarians cleverer than salad-munchers..? But, if plants are so intelligent – and have made us what we are – should we be eating such intelligent entities at all..? Where will it all end? [And is a tomato a fruit or vegetable..?]
** And research by Joanna Bowtell et al.  only adds to this view in demonstrating that supplementing the human diet with blueberry concentrate improved activation in brain areas associated with cognitive function in healthy older adults.
[Ed. – interestingly, although fruit-based diets may have begun the development of the human brain, Melania Lynn Cornish et al. propose that it’s seaweed-based nutrition that finished the job, after humanity diverged from the chimpanzee, our nearest living relative.]
DeCasien, A. R., Williams, S. A., & Higham, J. P. (2017). Primate brain size is predicted by diet but not sociality. Nature Ecology & Evolution, 1(5), 0112. https://doi.org/10.1038/s41559-017-0112
Dunbar, R.I.L. (1998) The social brain hypothesis. Evolutionary Anthropology 6 (5). pp 178-190.
Bowtell, J. L., Aboo-Bakkar, Z., Conway, M. E., Adlam, A.-L. R., & Fulford, J. (2017). Enhanced task-related brain activation and resting perfusion in healthy older adults after chronic blueberry supplementation. Applied Physiology, Nutrition, and Metabolism, 1–7. https://doi.org/10.1139/apnm-2016-0550
Cornish, M. L., Critchley, A. T., & Mouritsen, O. G. (2017). Consumption of seaweeds and the human brain. Journal of Applied Phycology. https://doi.org/10.1007/s10811-016-1049-3