Here’s a question. After a long week, you now you find yourself on a cold, dreary, rainy Saturday afternoon. Would you rather:
A) Be out collecting tasteless wild berries and gather edible green plants.
B) Be curling up on the couch in fuzzy socks with a good book, a cup of warm tea and a muffin.
It turns out the question could be moot if our ancestors hadn’t taken a big gamble with their food.
Researchers at Duke have published a new study in Science showing that early human foragers and farmers adopted an inefficient high-risk, high-reward strategy to find food.
In other words, they spent more energy in pursuit of food than their earlier ancestors and their great ape cousins. That might not be efficient, but they ended up bringing home much more calorie-rich meals that could be shared with the rest of their group. This strategy allowed some to rest or tackle other tasks while food was being acquired.
“Hunting and gathering is risky and inefficient, but the rate of return is enormous,” said Herman Pontzer, an associate professor of Evolutionary Anthropology at Duke University. “We can share our food, and because we took in so many calories before noon, we can hang out around each other in this new space, a free-time space.”
You could call it the dawn of the couch potato, although it’s likely furniture such as couches were not invented yet.
Back to the study.
The first thing to understand what scientists call a food energy budget. Those energy budgets depend on how much food energy is absorbed, and how much time and energy are spent obtaining food. And as you can imagine, humans spend a lot of energy. We have big brains that eat up a lot of calories, we live a long time, we can have long pregnancies that produce big babies, and these babies rely on adults for a long time.
In short, it takes a lot to keep us going. And humans were thought to maintain their high-energy lifestyle in one of two ways: they could be super-efficient, spending little time and energy finding food – in part due to the use of tools and technological advances, or they could spend a lot of energy to quickly bring home a lot of food, sacrificing energy efficiency.
To understand how humans obtained that extra energy, Pontzer and other researchers compared the energy budgets of wild gorillas, chimpanzees and orangutans with that of populations of Tanzanian hunter-gatherers (Hadza) and Bolivian forager-horticulturalists (Tsimane).
Hunter-gatherers and forager-horticulturalists both gather food from wild plants and animals, but the Tsimane also produce small-scale crops. The researchers found that hunter-gatherers and forager-horticulturalists are inefficient, high-intensity foragers. Think of a car racing out to grab a stack of pizzas. There’s a lot of energy used to get the food, but it’s done quickly and there’s a lot of calories obtained. Rather than minimizing their costs, they take a risk to maximize their rewards.
You can think of chimpanzees, gorillas and orangutans as more like riding a bicycle to the store to get lettuce and fruit. They are essentially herbivores who eat very little, if any, meat. Their strategy is one of low risk, low rewards: their food is easy to find, but it’s fibrous, low in energy, and it takes a lot of time to get enough of it.
The Hadza hunter-gatherers and the Tsimane forager-horticulturalists both eat high-calorie foods that are harder to get. They spend a lot of energy hunting, gathering, planting and harvesting, but can quickly bring home a nutritious lunch. '
Perhaps even more important, they bring home enough to share. Pontzer believes sharing provides a safety net, enabling some group members to take risks in food gathering, including hunting big game.
It’s high-risk, high-reward, but if they come back empty-handed there are others who have food to share. In addition, the sharing of food allows other group members to stay home and do other things because they have the precious community called: free time.
“This slight shift in the way that we go about getting our food has fundamentally made everything else possible,” Pontzer said. Free time allows group members to communicate about things other than food. It allows for experimentation, for learning, for creativity, for play, for culture.
The flip side of all this, of course, is that you must be careful with that pantry or refrigerator filled with tasty, high caloric foods.
““We are built to try and get a lot of food,” Pontzer said. “We are hugely ravenous and inefficient, and that's how we've evolved for two million years.”
In other words, the energy budget requires you to burn off energy as well as take it in. Something to think about as you curl up on the couch!