Why were our ancestors cannibals?

For homo antecessor, consuming conspecifics was obviously more rewarding than hunting

Early humans of the kind Homo antecessor were cannibals, as finds in Spain occupy. But why? © J. Rodríguez
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Creepy meal: Just under a million years ago, cannibalism apparently belonged to the everyday lives of our ancestors, as bones in Spain suggest. Accordingly, the homo antecessor consumed several of his fellow human beings there. The possible motivation for this has now been determined by researchers. Their analyzes show that it was not lack of food that was the cause, but opportunism: human food was easier to obtain than game.

Cannibalism is considered a great taboo today, yet there is the consumption of conspecifics both in the animal kingdom and among humans. So bone finds prove that the Neanderthal did not shy away from cannibalism. In times of emergency, however, modern humans have already more often killed their equals, for example in the fatal Franklin expedition of 1845.

Why do you eat conspecifics?

"Cannibalism is an ancient and widespread human practice, " states Jesus Rodriguez and his team at the National Research Center for the History of Humanity in Burgos, Spain. But the possible reasons and the importance of the consumption of fellow human beings are hotly debated. For example, some researchers in cannibalism see primarily a way to meet calorie needs, while others consider cultural and social reasons to be more important.

Skull fragments of the Homo antecessor from the Gran Dolina site. © José-Manuel Benito / Public domain

"Why people eat each other is a complex question, " the researchers said. To answer them, Rodriguez and his team have now undertaken one of the oldest and best-known sites of human cannibalism - the Gran Dolina Cave north of the city of Burgos. It contains a large collection of fossils attributed to Homo antecessor, who lived around 900, 000 years ago.

Bite marks, fractures and exhausted bones

The scary thing about it: The human bones discovered in the site reveal clear indications of cannibalistic practices: "The human bodies have been gutted, gutted and boned, " explain Rodriguez and his team. "The long bones were broken to get to the bone marrow. In addition, bite marks are documented on several human and animal remains. "Display

According to the researchers, the pattern of the damage indicates that representatives of the Homo Antecessor consumed the entire body of dead people - including the brain, organs and bone marrow. Even the rib bones were chewed and sucked, as revealed by corresponding bite marks.

It was not a famine

The remarkable thing about these testimonies for early human cannibalism: the abundant animal bones in the same layer of evidence prove that these early humans did not suffer from hunger. It was probably not the hardships that turned her into cannibals. As Rodriguez and his team calculated, the amount of food covered by the animals alone would have been enough to feed 20 people for three months.

Unusually also: In comparison to the animal bones, human bones with traces of processing in the fundus layer are clearly overrepresented. "While animals were consumed in proportion to their abundance in the environment, humans were consumed in higher proportions than their density in this environment, " the researchers say. In other words, they were chosen deliberately.

Man as the most rewarding prey

But why? To find out, the scientists used a classic prey-choice model. This assumes that an animal or human will choose the prey, which provides him with the most energy with the least effort. A prey that is high in calories but hard to kill can be just as rewarding as a calorie-poor but easy-to-catch prey.

When the researchers applied this model to the skeletal finds of Gran Dolina, it became clear that although human remains account for only about 13 percent of the calories of all the organisms consumed there, consideration is given to the effort, say the ancestors first of all. Because in contrast to fast or defensive prey such as deer or Nash rnern were the most youthful or at least still young human victims rather easy prey, say Rodriguez and his team.

Just as chimpanzees tend to eat and eat juveniles in conflicts between groups, these early humans may have been killed in a conflict and then consumed as food.

Become a meal through early death?

Thus it is no coincidence that the homo antecessor became a cannibal it seemed worthwhile for him more than hunting for animals. But that does not mean that these early humans also deliberately killed their victims, as the researchers emphasize: "The simplest explanation, however, could be that these victims belong to the same group as the cannibals And died a natural death, "said Rodriguez and his team.

As they explain, ethnographic data show that hunter-gatherers have very high mortality rates among adolescents and young adults. "For example, among the! Kung, Hadza and Ache, between 40 and 65 percent of the tribesmen die before reaching adulthood, " the researchers report. The homo antecessor could therefore have considered the early death of his group members just as practical and taboo-free as welcome extra food. (Journal of Human Evolution, 2019; doi: 10.1016 / j.jhevol.2019.03.010)

Source: Centro Nacional de Investigacion sobre de la Evolucion Humana (CENIEH)

- Nadja Podbregar