In 2018, a researcher calculated the calories from cannibalism and won an Ig Nobel Prize for revealing why prehistoric humans may not have eaten each other simply for food

Cannibalism is usually associated with extreme hunger, survival or ritual, but archaeologist James Cole approached the subject with a different question, if prehistoric humans consumed other humans, how much nutritional value did a human body actually provide?

In a study published in Scientific Reports in 2017, Cole calculated the potential caloric value of an adult human body and compared it with the nutritional value of animals that prehistoric hunter-gatherers could have consumed. The results suggested that humans were a relatively poor source of calories compared with many larger animals.

The unusual research later earned Cole the Ig Nobel Prize for Nutrition, an award recognising research that first makes people laugh and then makes them think.

How many calories are in a human body?

Cole's study, titled Assessing the Calorific Significance of Episodes of Human Cannibalism in the Palaeolithic, attempted to quantify something that is difficult to establish from archaeological remains, the nutritional return from consuming a human.

Using previously published data on human body composition, Cole estimated the caloric value of different tissues and calculated that an average adult male human body contained approximately 125,822 kilocalories.

That figure represented the potential energy available from the body's tissues rather than suggesting that every part would necessarily have been eaten.

Cole then compared the human estimate with the caloric value of animals that were available to Palaeolithic populations.

Humans were not the most rewarding meat source

The comparison produced the central finding of the research. A human body contains a substantial amount of energy, but the caloric return becomes much less impressive when compared with larger prey animals.

Cole estimated that a 9mammoth could contain roughly 3.6 million kilocalories, many times the energy available from a single human body.

The same basic pattern applied to several other large animals. Larger prey could provide dramatically greater quantities of food, meaning that if prehistoric people were simply looking for the maximum caloric return, hunting large animals would generally have made more nutritional sense than consuming another human.

This did not mean that humans were nutritionally worthless. Rather, the study questioned whether food alone could adequately explain every archaeological example of prehistoric cannibalism.

The archaeological evidence for cannibalism

The study was based on a broader archaeological question. Researchers have found human remains at several Palaeolithic sites showing signs of deliberate processing.

Archaeologists can look for cut marks, fractures, burning and other modifications that may indicate that bodies were processed in ways comparable to animal carcasses.

One important example is Gran Dolina in Spain, part of the Atapuerca archaeological complex. Researchers have reported evidence that Homo antecessor individuals were butchered and consumed there.

Other sites have produced evidence that has been interpreted as possible cannibalism, although the reasons behind these episodes are much harder to determine.

Finding evidence that a human body was processed does not automatically reveal why it happened. That is where Cole's calorie calculations become relevant.

Was prehistoric cannibalism really about hunger?

Cole's research suggested that nutritional necessity should not automatically be assumed as the explanation. If a prehistoric group had access to large animals, a human body offered a considerably smaller caloric return.

This does not rule out survival cannibalism. Under extreme circumstances, any available source of calories could become important.

But Cole argued that the nutritional calculations could support alternative explanations for some archaeological examples, including social, cultural, ritual or aggressive behaviour.

In other words, prehistoric cannibalism may sometimes have been about what people believed, how they treated the dead or their relationships with other groups rather than simply about filling an empty stomach.

The Ig Nobel Prize for cannibalism research

Cole's unusual subject eventually received one of science's most unusual honours. He won the Ig Nobel Prize for Nutrition in 2018 for calculating that the caloric intake from a human-cannibalism diet was significantly lower than that from most traditional meat diets.

The Ig Nobel Prizes, organised by Improbable Research, are intended to celebrate research that makes people laugh and then think. Cole attended the ceremony to receive the award.