Many foods humans consume are indigestible or toxic without first being processed. Cassava (also called manioc or yuca), a staple in South America, Southeast Asia, the Caribbean and Africa, contains a cyanide derivative that is noxious if eaten raw. Other common vegetables (eggplant, potato), beans (kidney, castor, lima, cacao), nuts (bitter almonds, palm nuts), and seeds (cycad seeds, rice) are either lethal, toxic, or taste bitter. But once pounded, soaked, ground, leached, fermented, or cooked they become palatable. Wheat, barley, oats, and corn are rarely eaten without pre-digestive treatment.
Processing extends the lifespan of food. During nongrowing seasons, both hunter-gatherers and agriculturalists rely on stored food. Much of the world would have remained uninhabitable if humans hadn’t perfected storage. People who live at high latitudes or elevations, or have refrigeration, can preserve food for some period by keeping it cold. Otherwise, it must be dried, salted, or smoked, and then secreted in a protected place so vermin don’t get to it first.
The evolutionary legacy of softening and breaking down food left its testimony on the human body. Over time, the thick, massive teeth of our early Homo ancestors were replaced by much smaller, more refined, thinner-enameled teeth. Robust skulls with bony perturbances that anchored chewing muscles gave way to more delicate faces and jaws. As our heads functioned less to buttress a built-to-chew mastication system, they made room for brain expansion. Eating partially predigested food also relaxed the need for a large and metabolically costly gastrointestinal tract, evidenced by our relatively small gut.
Eating predigested food also saves time that would otherwise be spent chewing. Chimpanzees spend almost half of daylight hours chewing highly fibrous fruits, a substantial part of their diet. Humans today spend far less time chewing—about 5 percent of their day, or about 35 minutes. This dramatically further decreases with industrially processed and highly refined food that has little to no fiber.
Humans, for most of our existence, lived as hunters and gatherers. Today only a small number of societies still rely on foraging. But studying how these groups adapt to different environments helps evolutionary anthropologists understand how our species became so widespread and successful.
WOMEN’S COOPERATIVE WORK
The excitement is palpable when hunters bring meat into a Pumé camp. Like many foragers who live near the equator, the Pumé live in small groups of about 70 people, relocating their camps and building shelters as the seasons demand. Times are good during the dry season when food is plentiful. But during the rainy season, life changes dramatically.
Once a week or so, hunters return to camp with a cayman, anteater, deer, or large bird. While meat is valued for its protein and fat, plants get the Pumé through the wet season. During this lean time of the year, women and children forage almost exclusively for roots and bring in about 85 percent of the calories. In most temperate and equatorial environments like this one, roots, tubers, seeds, beans, nuts, fruit, and berries are all staples for survival. Pumé women and children supply these bottom-line calories and process them into edible foods.
