Plant Cuttings

Fruit, true food for thought*

Some say fruit is connected to human intelligence, but is the idea a peach or completely bananas?

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.

Euler diagram representing the relationship between (botanical) fruits and vegetables. Botanical fruits that are not vegetables are culinary fruits.
Euler diagram representing the relationship between (botanical) fruits and vegetables. Botanical fruits that are not vegetables are culinary fruits. Image Hopefully acceptable username / Wikipedia

How does that help? Well, we are beginning to realise that plants are highly intelligent. So, ingesting such intelligent life forms can only fuel our own intelligent development. Rather fanciful?

Yes.

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..?]

* An idea or issue to ponder.

** And research by Joanna Bowtell et al. [17] 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.]

References

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

About the author

Nigel Chaffey

Nigel is a botanist and full-time academic at Bath Spa University (Bath, near Bristol, UK). As News Editor for the Annals of Botany he contributes the monthly Plant Cuttings column to that august international botanical organ. His main goal is to inform (hopefully, in an educational, and entertaining way...) about plants and plant-people interactions.