Concerns and questions about the nutritional needs of ancient cannibals

From a modern human’s perspective, cannibalism seems like a particularly monstrous course of action. While my kids have heard about animals eating members of their own species, the idea that humans have been known to eat each other was still surprising enough that my four-year-old felt the need to fact-check this concept with his mom. Nonetheless, humans have been eating each other since the Stone Age, with just enough regularity that researchers believe there may have been a pattern or repeating motivation to do so. Such as… nutrition?

Calories worth the cost?

While the tragic events surrounding Uruguayan Air Force Flight 571 famously demonstrate that cannibalism can keep you alive, researchers wanted to know if it was actually well-suited for that job. Were repeated instances of cannibalism in the archaeological record, as indicated by butchered bones or opened brain cases, simply because human bodies were a good source of food, even if you hadn’t been stranded in the mountains? After a thorough survey of earlier measurements of the calorie content of human anatomy, the answer was that humans aren’t especially nutritious. A whole human body, from the brain to the bones, really only yielded around 126,000 calories, much less than the 600,000 calorie bears living in the same ecosystem.

This suggests that humans probably weren’t being eaten because of a sense of nutritional efficiency, and were thus on the menu for other, possibly more ritualistic, reasons. However, this assumes that, outside of obviously skinny compatriots, these early humans could really assess the potential nutrition of eating one creature over another. Even in a highly measured, labeled world, many people today might be surprised about the caloric gap between a gram of chicken breast versus thigh meat, much less the 100-calorie difference between lamb loin and pork loin.

Difficulty measuring meat

Part of the difficulty in measuring meat is how much cooking it changes its nutritional value. Like starches, the sugars and proteins in meat open up when they’re cooked, allowing digestive enzymes a better chance to break them down into useful nutrients. Collagen also softens, making the meat literally easier to chew and ingest. Even mice, who don’t naturally encounter cooked meat, will favor it over raw options.

Our ancient ancestors likely had access to fire by the time they were eating each other, which begs a question about how the calorie count of human flesh was calculated. Most of the numbers came from older literature, measured in a time when calories were measured simply by burning the food in a container to see how much it heated water. Modern food measurements are a little more sophisticated now, doing a better job of how food will be digested. If the human body were remeasured to modern standards, we still might not match the caloric bounty of a one-ton short faced bear, but properly roast thighs might not seem like such a waste after all.

Source: Cannibals Weren't Calorie Counters, But Humans Aren't Very Nutritious by Shaena Montanari, Forbes