Evidence of cannibalism among past human species goes back almost one million years. But what made our ancestors eat each other? Probably not so much our nutritional value as it's sorely lacking, says University of Brighton archaeologist James Cole. From Erika Engelhaupt's article in National Geographic:
“When you compare us to other animals, we’re not very nutritional at all,” says study author James Cole of the University of Brighton, who published his work Thursday in Scientific Reports.
According to his estimates, boars and beavers pack about 1,800 calories into each pound of muscle compared with a measly 650 calories from a modern human. That’s about what would be expected based on our overall size and muscularity compared to other animals, he says.
So, Cole asks, if humans aren’t especially valuable in terms of prey, why eat them? After all, unless they are sick or dying, they wouldn’t be easy to hunt.
“You have to get together a hunting party and track these people, and then they aren’t just standing there waiting for you to stab them with a spear,” says Cole.
Instead, Cole argues that perhaps not all ancient cannibalism was for filling bellies; it may have also served various social functions for early humans and their ancestors...
“I agree with [Cole] that Paleolithic cannibalism was probably more often practiced as a ‘choice’ rather than mere ‘necessity,’” (says anthropologist Silvia Bello of the Natural History Museum in London). “I think, however, that to find the motivation of the choice is a very difficult matter.”