Prehistoric cannibals weren’t in it for the calories

Caloric analysis of the human body suggests cannibalism would not have been nutritionally efficient.

In the limited fossil evidence we have for prehistoric hominins, a group that includes humans and our immediate ancestors, there is surprisingly abundant evidence of cannibalism. So why were these individuals eating each other? A new study in Scientific Reports suggests it probably wasn’t for nutritional reasons. The research provides a calorie value for the human body in comparison to other animals eaten at the time. Archeologist James Cole found that the human calorie count is significantly lower than that of mammoths, woolly rhino, and species of deer, which are known to have been consumed by hominins. Considering the difficulty in hunting another human, these results suggests that cannibalism may not have been for nutritional reasons as has been previously reported.

We spoke to Cole about the work.

ResearchGate: What motivated this study?

James Cole: I have always been interested in trying to understand the behaviors and cognitive abilities of our human ancestors such as the Neanderthals. In modern human societies, the act of cannibalism has a range of motivations from survival, psychotic (as in Hannibal), warfare, medicinal, dietary and ritual. We know that our hominin ancestors have practiced cannibalism for at least 1 million years. So I thought it would be an interesting to understanding whether they may have had the same range of motivations for cannibalism as we do.

Previous interpretations often say that hominin cannibalism was “nutritional cannibalism,” which in this instance means that the human was consumed as part of a regular diet. I wanted to know how nutritious a hominin was in relation to other fauna that were regularly eaten by our hominin ancestors.

RG: Can you tell us what you found?

Cole: I found that humans (and by inference other hominins) are about what we expected in terms of an animal with our body size and weight from a calorie perspective: about 32,000 from the muscle tissue. Whilst this is perhaps not surprising, what was surprising was that some faunal remains returned a far higher calorie count than hominins. For example, a horse would provide about 200,000 calories from muscle tissue. This is important, because a single large faunal animal can give a higher calorific return than a group of cannibalized hominins. This could indicate that cannibalism in the prehistoric period may well have been driven by social factors, such as resource and territory defense, and not nutrition.

RG: How did you achieve these results?

Cole: I did an extensive literature review and developed a calorific model of the human body from studies looking at the chemical composition of the human body. I took the fat and protein values from those studies and used them to work out the calorie equivalents. The faunal calorie content was also derived from previously published literature.

RG: How widespread was prehistoric cannibalism?

Cole: Given the sparse nature of the hominin fossil record, there are a surprising number of hominin remains that have some form of anthropogenic modification associated with them. There is an excellent paper reviewing the evidence for prehistoric cannibalism in Western Europe from Homo antecessor to the Bronze Age. It would appear that cannibalism may have been fairly common within hominin societies (as it is within modern human societies today).

RG: Do you think the nutritional value of modern humans would differ to that of prehistoric times?

Cole: Yes, there is bound to be a difference between the prehistoric human values and those of today given the vastly different lifestyles and diets. However, this study is useful as a proxy indicator. I use it as a minimum value in my study. Nevertheless, this has never been calculated to this extent before, so I think it is still a useful contribution to knowledge. I would also be very happy if fellow scholars could suggest ways to refine the model and make it more accurate, that is after all what good science is all about. All of my calculations are available in the paper.

RG: Why is the difference in nutritional value evidence that humans weren’t eating humans for nutrition? They wouldn’t have known, right?

Cole: They would not have known the calorie numbers of course, but they would have had a good idea about the volume of meat available on fellow hominins versus other faunal remains. Also, tracking down another human species as intelligent as you and able to fight back as well as you, that is a lot of effort to go to for relatively little calorific return. In contrast, you could kill one horse and get significantly more meat and calories. So we need to question whether we can dismiss the possibility of social or cultural drivers for Palaeolithic cannibalism before defaulting to the meat for meat’s sake option, which in turn cannot be entirely dismissed. In addition, we know that hominins, like Neanderthals, were extremely complex behaviorally, they were a symbolic species with jewelry, cultural diversity in terms of stone tool manufacture, and they had a complex attitude to the burial of their dead. Why would they not have an equally complex attitude to cannibalism?

RG: If they weren’t being killed purely for cannibalism, what do you think was happening?

Cole: It’s not that the hominins were not being killed for cannibalism. It’s rather that the reasons for cannibalism may not have been nutritionally driven, but rather socially driven: tensions between groups, or messages around things like resource defense. So, although this can’t be completely discounted, I don’t necessarily think that hominins were being cannibalized for their meat alone, but rather that there were more complex social and potentially cultural influences that we don’t know about.

Featured image courtesy of Trey Ratcliff at stuckincustoms.