This article originally appeared on Motherboard.
If you were a Paleolithic hominin living in western Europe tens of thousands of years ago, you had a few things to worry about: finding the right cave to live in, wooing a mate, and possibly being cannibalized by your neighbour.
Our ancient ancestors did engage in cannibalism, but it wasn't only when other food sources were scarce and they had no other choice. A new paper published in Scientific Reports tells us that there were probably complex motivations—beyond the calories—that drove early hominin species like Neanderthals and Homo erectus to occasionally dine on each other.
As for human flesh, "it's just that we aren't terribly nutritious," study author James Cole, a senior lecturer in archeology at the University of Brighton, told me over the phone.
Presumed motivations have ranged from dietary to warfare cannibalism and psychotic cannibalism, "like Hannibal Lecter"
To reach this conclusion, he compared the caloric content of animals commonly found in the same spots where ancient cases of cannibalism have been confirmed in western Europe, like Les Pradelles in France. The study explains that downing a mammoth, auroch, or bison would get you about 2,000 calories for every kilogram of meat. Your average human, on the other hand, is only about 1,300 per kilogram of muscle: not necessarily worth the effort it would take to hunt down and kill a meal that could potentially outwit you along the way.
"If they're my own species, they can think the way that I think. They can run the way that I can run, and they can fight the same way that I can fight," said Cole. "That could be quite a hard task, to hunt and kill a member of my own species for not very much calorific return."
But cannibalism did happen. Repeatedly. The study takes a look at nine different archeological digs where evidence of early hominins eating a member of their species existed, back to almost a million years ago. Before Cole's paper, most cases were assumed to be simply for nutritional value. But when you line up the costs and benefits, he argues, there probably was more at play.
"It might be: 'We've got our territory, these people are interlopers and they're trespassing on it. We need to go and sort that out,'" presumably by eating the intruders, said Cole about one potential motivation. He also cites evidence of ritualistic cannibalism in the example of the Gough's Cave dig in Somerset, England. The site is only 14,700 years old, and held the remains of five consumed individuals. It appeared that, while the rest of the bodies were eaten, the skulls were cleaned of flesh, preserved and "carefully modified to make skull-cups," says a paper by Natural History Museum researcher Silvia Bello.
"There would have been some kind of ritual attached to the skulls of these individuals, but the bodies were consumed as part of the cannibalism act," said Cole.
Over the years, we've thought up a ton of different reasons why we would eat another member of our species. Cole explains that the presumed motivations have ranged from dietary, medicinal, ritual, to warfare cannibalism and psychotic cannibalism, "like Hannibal Lecter."
His work suggests that our early ancestors were subject to a range of motivations—they didn't fit one mould. "These human species are as behaviourally diverse as we are today," he said.
We know the Neanderthals had jewelry and buried their dead, and so extending that level of thinking to their cannibalistic tendencies might not be a stretch.
"I feel that we need to challenge ourselves within the archeological community, with scientific rigour behind us, to actually embrace that complexity," said Cole. It wasn't all about the calories.