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Key points
- Hominids started to grow bigger brains 2.5 million years ago.
- A bigger brain requires extra energy to support it.
- Before the use of fire, fermented food may have provided a reliable source of extra calories.
“Don’t cry over spilled milk. By this time tomorrow, it’ll be free yogurt.” —Stephen Colbert
Some 2.5 million years ago, our hominid ancestors started to grow bigger brains. Over the next several millennia, our brains tripled in size. It led to a new creature, Homo Sapiens, that eventually ruled the planet.
Brains demand copious amounts of energy, and growing a big one means the possessor must absorb extra calories. One way to get them is to develop a giant gut, like a horse, that can take its time to eke out every calorie from the meager pickings on the savannah. Yet our guts are shorter than those of our simian cousins.
A popular theory says that the advent of cooking helped to break down food and improved our ability to salvage extra calories. But man-made fire and cooking came about a million years too late to explain the phenomenon. It’s also likely that we needed bigger brains to manage fire in the first place, so this theory seems to put the cart before the horse.
A New Theory
A recent study from Erin Hecht of Harvard and Katherine Bryant of Aix-Marseille Université proposes an alternative brain-building theory: The energy boost came from fermented food. If true, it means that from the very beginning of hominid history, our brains have been linked to microbes.
It’s not a crazy theory. All animals depend on gut microbes to help digest their food. Animal intestines can easily absorb protein and simple carbs but struggle to break down the complex carbs called fiber.
However, fiber is a major component of many of the veggies in our diet. So, ever since animals have inhabited the planet, they have recruited gut microbes to ferment fiber into useful fatty acids. Horses, for instance, can convert a miserly diet of simple grasses into enough energy to outrun a mountain lion, courtesy of nine gallons of microbes that they haul around in their cecum.
But our hominid ancestors seemed to have stumbled onto a better plan: let the food ferment before eating it. With partially digested food, a smaller gut could support a bigger brain.
An important part of that fermented food cache was meat. Most archeologists believe that eating meat was a big turning point in human evolution. However, humans are notoriously underpowered in the tooth and claw department, and the archeological record doesn’t show us to be big hunters in the early days of our development.
Scavenging was more our speed, but the pickings are thin after the big carnivores have had their fill. That is why the smart money is on “power scavenging”—a delightful term for getting a gang together to chase the carnivores away while there’s still some meat left on the bones.
There is evidence that these hominids brought tools to the feast, sliced off the meat, and then took it back home, traveling up to 10 kilometers to keep a safe distance from predators and other scavengers. Piled up for storage, fermentation could occur spontaneously, extending the shelf-life and improving digestibility. Fermenting food increases the bioavailability of its nutrients, making them easier to absorb. Fermenting can also destroy toxins and create vitamins.
Storing ferments solves another problem: Bigger brains require continuous feeding. Since fermented food can last for years, a stockpile guarantees a continuing source of energy for mental maintenance. Best of all for our comparatively dim ancestors, it would not take a lot of foresight to pull this off; fermented food is common in nature.
Refining the Process
Fermented meat sounds disgusting until you realize that ham, pickled herring, prosciutto, pepperoni, chorizo, and salami are all delicious examples of fermented meat. In fact, much of the fermented food we eat today, like soy sauce, vinegar, and chutney, are condiments that we add to foods to punch up the flavor. Humans are fairly unique among animals when it comes to enjoying the sour kick of ferments, confirming a long-time pattern of consumption.
Before refrigerators were invented, fermenting was the primary way to preserve food. In the 1940s, home refrigerators started to become widespread. That spelled the end of many fermented foods. Why make kraut when a cabbage can last for weeks in a fridge?
Other changes came with government regulation of food processing. Food safety organizations around the world, including the FDA, offer complicated and often conflicting regulations for fermented foods, causing many manufacturers to simply pasteurize their ferments, destroying all microbes. This effectively kills dangerous Clostridium botulinum bacteria, but it takes out the beneficial microbes at the same time. Intriguingly, even pasteurized ferments seem to offer some health benefits, although the mechanism is murky.
Refrigeration and pasteurization have massively altered a diet that has served us well for untold millennia. Some researchers have suggested that the modern deprivation of dietary microbes—our old friends—is associated with today’s increased rate of allergies and autoimmune diseases. The “old friends” hypothesis is gaining experimental support as we begin to better appreciate the role of microbes in our bodily and mental health.
A New World of Ferments
Fortunately, in the last decade, there has been a renaissance of fermented foods and people are relearning to crave tangy yogurt, kefir, kraut, pickles, and other ferments from around the world. Just in time, too: Fermented foods have been shown to improve cardiovascular disease and certain cancers. They also help to lower inflammation and in the process, they can improve cognition and mood.
Most people can benefit from fermented foods, although if you are having a flare-up of IBS or IBD, you should wait for that to subside. A leaky gut can allow microbes to enter the bloodstream, which is also problematic for people with compromised immune systems.
Otherwise, try to get some ferments into your diet. If you aren’t used to them, start slowly. They can get you back to your ancient roots, and they might do your brain some good. It’s food for thought.
References
Bryant, K.L., Hansen, C. & Hecht, E.E. Fermentation technology as a driver of human brain expansion. Commun Biol 6, 1190 (2023).
Mukherjee, Arghya, Beatriz Gómez-Sala, Eibhlís M. O’Connor, John G. Kenny, and Paul D. Cotter. “Global Regulatory Frameworks for Fermented Foods: A Review.” Frontiers in Nutrition 9 (May 23, 2022): 902642.
Mukherjee, Arghya, Samuel Breselge, Eirini Dimidi, Maria L. Marco, and Paul D. Cotter. “Fermented Foods and Gastrointestinal Health: Underlying Mechanisms.” Nature Reviews Gastroenterology & Hepatology, December 11, 2023, 1–19.
