“Some scholars believe,” writes Yuval Noah Harari in his book Sapiens, “there is a direct link between the advent of cooking, the shortening of the human intestinal tract, and the growth of the human brain.” Harari argues that technologies around cooking allowed human intestinal tracts to evolve toward simplicity. Cooking food broke down compounds in foods that were harder to digest and neutralized pathogens that could have made us sick. As we learned to use fire, boil water, and create stone or dirt ovens, we made food more healthy, safer, and easier on our digestive systems which meant that we didn’t need to have such a robust digestive tract.
Harari continues, “Since long intestines and large brains are both massive energy consumers, it’s hard to have both.” When our intestines didn’t need to be so beefy, it was advantageous for humans to evolve with shorter, more streamlined guts. The energy saved in the gut could go toward other organs. Specifically, in the view Harari explains, the extra energy could be used to maintain a larger brain.
This makes me wonder, is all of human evolution a race toward a bigger brain? It is true that taller men are more likely to be elected president in the United States and that the typical image of a sexy man is a taller and more muscular individual (like Thor or Captain America), but for how long in human evolutionary history have tall bodies and large biceps been the most advantageous features for survival? Perhaps our desire for big brawny genes is leftover from our super quick ascendancy to the top of the food chain. Perhaps, as Harari’s quote eludes to, bigger brains have been the most advantageous feature for human survival for most of our history. Perhaps that truly is still the case.
An argument that Harari makes throughout the book is that humans have come to dominate the planet through our improved cognitive, reasoning, and social skills, which are all dependent on our brains. In this sense, evolutionary pressure has been toward larger brains, so all of human evolution is in some ways a race toward bigger brains. Shortening our gut allowed for bigger brains, giving up musculature allowed for more brain energy, standing on two feet allowed us to better survey the land – to provide our big brains with more data. We are not evolving to be better fighters, faster runners, or to physically occupy new niches. We are (and have been) evolving to better support better brains.