Cannibal feast on the Island of Tanna, New Hebrides by Charles E. Gordon Frazer (1863-1899).

Our Ancestors Were Cannibals – and Probably Not Because They Needed the Calories

James Cole / The Conversation

In the recently released horror movie Raw, a lifelong vegetarian teenager arrives at a veterinary school and, after being forced to consume a rabbit kidney at a student initiation ritual, discovers a deep desire to eat human flesh. Most of us are fascinated with cannibalism – and there are many examples of brutal and dark dramas exploring the topic, including Silence of the Lambs and Hannibal.

But in real life, cannibalism hasn’t just been practised by bloodthirsty psychopaths. Common motivations for eating human flesh include periods of starvation , warfare and ritualistic behaviour . And it hasn’t been all that uncommon – many of our ancestors were actually cannibals. But exactly why has remained a bit of a mystery. In a new paper, published in Scientific Reports , I have now started to answer the question.

We know from archaeological evidence that cannibalism took place across prehistoric western Europe. A recent review – covering a period from 960,000 years ago to the Bronze Age – shows that it must have been fairly common, given the number of hominin remains that show evidence of cut marks and human gnaw marks. We have also found many broken long bones – indicating an effort to get to the marrow.

Model of a male Homo antecessor of Atapuerca mountains possibly practicing cannibalism. (Ibeas Museum, Burgos, Spain)

Model of a male Homo antecessor of Atapuerca mountains possibly practicing cannibalism. (Ibeas Museum, Burgos, Spain) ( Jose Luis Martinez Alvarez/ CC BY SA 2.0 )

Nutritional value of human flesh

We can’t know exactly why these societies were cannibalistic. But researchers have broadly interpreted it to be “ nutritional cannibalism ”, forming a regular component of a species’ overall diet. This is because most of the marks found on the skeletal remains relate to processing the carcass for food, such as getting to the marrow. If the bodies were cut up for ritual purposes, such as defleshing, we would expect to see more scraping marks along the bone as they were cleaned of their flesh. But despite assuming that corpses were eaten for nutrition, we still don’t have a clear idea of how nutritional (in the sense of calories) humans actually are.

Partial skull found at Gough's Cave, Somerset, England. Facial Remains showing cutting-marks, where the meat has been removed, a clear sign of cannibalism.

Partial skull found at Gough's Cave, Somerset, England. Facial Remains showing cutting-marks, where the meat has been removed, a clear sign of cannibalism. ( José-Manuel Benito Alvarez/ CC BY SA 4.0 )

I attempted to find out by looking at cannibalism in the Pleistocene – a period from about 2.5m to 11,700 years ago, often broadly referred to as the Ice Age. This study includes human species such as ourselves ( Homo sapiens ), Homo Neanderthalensis , Homo erectus and Homo antecessor .

I started by creating a “nutritional template” for the human body by incorporating data on its chemical composition . This data provided the protein and fat content of each body part, which I then converted into calorie values. One gram of protein is about four calories and one gram of fat is about nine. However, as these measurements come from modern humans we cannot be sure exactly how they would vary for related human species. Neanderthals, for example, had slightly greater muscle mass.

Chemical composition of adult human body.

Chemical composition of adult human body. ( Mitchell, Hamilton, Steggerda, and Bean )

Nevertheless, I then compared these proxy values to those of animal species such as mammoth, bison, horse and reindeer, which we know that our ancestors often consumed. Indeed, archaeologists have found plenty of such animal remains at the same sites where there’s evidence of cannibalism. Interestingly, the calorific value of humans is not very high when compared to such animals. Indeed, when muscle masses are compared, a single horse can return approximately the same number of calories as up to six human individuals.

I argue that this suggests that the idea that early humans hunted and consumed groups of their own species only for nutritional purposes makes little sense – given that there were better options around. Indeed, we don’t have a huge number of remains from these species at hand, but within that small record there’s a relatively large sample of remains that appear to have been butchered. So it seems unlikely that cannibalism only occurred infrequently during periods of starvation.

Interpreting the data

So why then did prehistoric cannibalism occur? In short, there cannot have been a single reason. Each episode of prehistoric cannibalism will undoubtedly have had its own complex reason for occurring. But the poor calorific return of human flesh suggests to me that it may have been down to social or cultural reasons rather than the need to fill a gap in the diet. For example, it may be related to the social defense of resources or territory from interlopers who, having been killed, were then consumed.

Also, we shouldn’t underestimate the cultural and social sophistication of these species. Recent studies looking at the broader behavioural patterns for our ancestors, including the Neanderthals, have started to show that they may have been more culturally complex than previously thought.

Model of a female Homo antecessor of Atapuerca practicing cannibalism. (Ibeas Museum, Burgos, Spain)

Model of a female Homo antecessor of Atapuerca practicing cannibalism. (Ibeas Museum, Burgos, Spain) (Jose Luis Martinez Alvarez/ CC BY SA 2.0 )

Recent palaeo-genetic studies also hint at a more explicit and active degree of social interaction and interbreeding between hominin species than was thought possible. This includes interbreeding between our own species and the Neanderthals . For those genetic exchanges to have taken place, I would argue that there must have been not only a recognized biological similarity between the species, but also a cultural parity in terms of ability for language communication and symbolism. Indeed, it has already been recognized that different Neanderthal groups may have had distinct cultural and symbolic traditions and a varied attitude to the burial of their dead .

Why then would these species not also have had a variety of motivations for consuming members of their own species? Yet dietary motivations cannot be discounted as a driver for prehistoric cannibalism – it could be that these species were opportunists, eating anything they came across. But we should equally not discount the possibility that social motivations could have played an important role in determining why acts of cannibalism took place.

Homo neanderthalensis reconstruction. Matteo De Stefano/MUSE Science.

Homo neanderthalensis reconstruction. Matteo De Stefano/MUSE Science. ( CC BY SA 3.0 )

Top Image: Cannibal feast on the Island of Tanna, New Hebrides by Charles E. Gordon Frazer (1863-1899). Source: Public Domain

The article ‘ Our ancestors were cannibals – and probably not because they needed the calories by James Cole was originally published on The Conversation and has been republished under a Creative Commons license.


William Bradshaw's picture

There have been many cases of cannabilism wrongly attributed to us diploid humans. Many of these incidents of cannabilism were actually tetraploid humans killing and eating diploid humans as their main protein source. For example, in Germany around 4950 BCE there was evidence of sudden and massive amounts of cannabilism appearing in the area when none existed before that time. This was, in my learned opinion, due to the arrival of tetraploid humans into the area. They have been recorded in history as being cannabilistic as far back as 7,500 years ago (Book of Enoch). 

The moral question remains; since the tetraploid humans have a higher ploidy level than us, is it really cannabilism? This could be a source of debate but you are not permitted to know about tetraploid humans except through good sites like and I really applaud their excellent content in pursuit of the truth.

William H. Bradhaw, Dipl. T, CPIM

Why are we not permitted to know about tetraploid humans?

Please, enlighten us William:
Why do you consistently spell your name two different ways?
What does the alphabet soup stand for after your misspelled name?
Why are you hawking your questionable book on this site?

I think we'd all like to know.

I don’t think information about tetraploid humans are being withheld from the rest of us. It’s just not that common so we don’t hear about it very often. I don’t think tetraploidism has anything to do with cannibalism

Humans of today are more intelligent and have codes and law to govern human society.
In Ancient times, there were no rules, killing was not punishable. So killing other humans was also not bad for our ancestors. Coz today killing human and eating them is considered wrong by our religion and law.
At that time when law and religion was at its early form, killing and eating fellow human was not so wrong. Even many species of monkeys cannibalize.

Cannibalism was passed on to us by our ancestors.


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