One of the features that distinguishes primates – humans, great apes, monkeys … – is that they have a considerably large brain in relation to their body volume. Many scientists believe that this is due to the importance of the interactions between these mammals. It is the so-called “social brain hypothesis.” The complexity of relationships between primates would require the development of large brain tissue.
But research led by anthropologists at New York University has launched a new theory: primates could owe their significant brain size to fruit consumption.
Alex DeCasien, a doctoral student at New York University and lead author of the research, collected data on the diets and social lives of more than 140 species of primates around the world to find out what factors could be associated with the size of their brains. To his surprise, the only element that worked to predict which species would have larger brain masses had nothing to do with the size of the groups and their complexity, or with their sexual behavior.
The key was in the diet, specifically in whether or not fruits predominated.
Frugivores with more neurons
Scientists found that primates that eat mostly fruits have 25% more brains than those that base their diets on plants, leaves, and roots. However, the reason why this happens is not yet clear. DeCasien and his colleagues believe that the fruits are often scattered and can be difficult to locate; they often require peeling or are in hard-to-reach places. Overcoming these drawbacks requires complex cognitive skills that demand a remarkable brain.
Other specialists believe that the explanation lies in the large amount of energy that a primate needs to digest leaves and herbs, which translates into long digestions in which the animal can not do anything other than rest. In contrast, the fruit is easily processed and provides a lot of energy very quickly. That surplus energy would go directly to the brain, an organ that consumes a lot of fuel to function, especially among animals such as primates, which live in large groups in which survival requires a high cognitive capacity to learn to relate.
