Archaeological records show that prehistoric cannibalism dates back to nearly a million years ago but why did ancient man eat his own kind? Well, it wasn't so much because he had a taste for prehistoric human flesh, suggests a new study. If anything, this practice wasn't just about quelling hunger pangs, given that as prey, ancient humans were probably more trouble than they were worth and not as nutritionally satisfying as a mammoth steak.

Past studies have tended to regard this practice as one motivated by either dietary or ritualistic reasons however study author James Cole, a Paleolithic archaeologist at the University of Brighton, argues that the factors underlying prehistoric cannibalism are far more complex.

To reach this conclusion, he calculated the calorie value of an average human body, which was based on data taken from the autopsies of four modern adult males, and then compared the results to the calorie values of animal species found at prehistoric cannibalism sites.

According to his findings, a 65 kg (143.3 lb) male would yield around 32, 376 calories in muscle tissue (note: keep in mind these figures are a rough estimate since the real deal had a lot more muscle), which would hardly have kept a group of 25 adult Neanderthal or Pleistocene males full for half a day.

By comparison, a mammoth (3.6 million calories) was likely to see them through 35 days; a woolly rhinoceros (1.26 million calories) would last roughly 12 days; while a Steppe bison (612, 000 calories) would keep them sated for six days.

In addition to not ranking high on the nutritional totem pole, there's also the question of whether it was worth going through all the trouble of hunting and fighting a fellow hominin when there was much easier prey for the taking, says Cole. As he notes in the study, it would require more work to hunt a hominin than a small animal, such as a deer, given the former's ability to fight, run and think their way out of the situation.

That said, even though the returns of eating hominins don't seem to justify the efforts, there is reason to believe that this practice was more widespread than what the low number of cannibalism fossil sites suggests, says Cole. He points to the fact that even though there aren't many ancient human remains in the fossil record, there's still "a lot of evidence" of cannibalism – such as teeth marks on bones and long bone breakage (a sign that someone had tried to access the bone marrow within) – to indicate that it was not that uncommon a practice.

In addition, other researchers have also argued that prehistoric man's immunity to prion diseases (transmissible spongiform encephalopathies) was a result of cannibalism. If not for the repeated exposure to these pathogens, they would not have evolved to adapt to them, thus suggesting cannibalism was not that rare a practice.

So if prehistoric man wasn't that nutritious or easy to procure, what drove him to eat his own kind? Unsurprisingly, there's no clear cut answer to this question. Some of them could have taken a pragmatic approach and regarded those in their group that had died as an alternative source of meat so they wouldn't have to go out and hunt.

There's also the possibility that it was their way of asserting their claim over a particular territory or that it involved some kind of complex socio-cultural ritual that archaeologists have yet to figure out, as suggested by the cannibalized remains found at archaeological sites such as Gough's Cave in the UK, where victims' skulls were cleaned and then re-purposed as cups while the rest of their bodies were eaten.

In any case, what this goes to show, says Cole, is that one cannot assume that these early practices of cannibalism were due simply to nutritional or ritualistic reasons. Just as there are many reasons why modern humans practice cannibalism, could the motivations behind early man's cannibalistic proclivities not be just as complex? After all, far from being a brutish cave dweller who was motivated solely by simple basic needs, recent studies have shown Neanderthals to be far more sophisticated than assumed, as evidenced by the fact that they made jewelry and buried their dead.

"We know that modern humans have a range of complex motivations for cannibalism that extend from ritual, aggressive, and survival to dietary reasons," says Cole. "Why then would a species such as the Neanderthals, who seem to have had varying attitudes to the burial and treatment of their dead, not have an equally complex attitude towards cannibalism?"

The study was published in Scientific Reports.

Source: University of Brighton