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Cut marks on the shin

Photo: Briana Pobiner / Michael Pante / Trevor Keevil

Close evolutionary relatives of humans could possibly have been cannibals – at least that's what a study published in the journal Scientific Reports suggests. Cut marks on the remains of a 1.45-million-year-old tibia of a relative of Homo sapiens provide clues: The damage was caused by stone tools. It is the oldest example of this behavior, which is known with high certainty and specificity, according to a statement on the study.

"The information we have tells us that hominins probably ate other hominins at least 1.45 million years ago," said Briana Pobiner, a paleoanthropologist at the Smithsonian's National Museum of Natural History and first author of the study. "There are numerous other examples of species from the human family tree eating each other to feed each other. But this fossil suggests that the relatives of our species ate each other in order to survive, and further into the past than we realized."

The scientist examined the fossilized shin bone, which was found in Kenya, for clues as to which prehistoric predators might have hunted and eaten the ancient relatives of humans. She found traces that, according to the information, looked more like evidence of a "slaughterhouse".

Pobiner's team compared the shape of impressions and 3D scans of the sections with data from 898 individual tooth, slaughterhouse and trample impressions. The result: Nine of the eleven impressions can clearly be traced back to stone tools. The other two traces were probably bite wounds from a big cat, with a lion being the closest match.

According to Pobiner, cannibalism is the most likely scenario due to the way the cuts were made. "These cut marks look very similar to what I've seen in animal fossils that have been processed for consumption," Pobiner said. "It seems very likely that the flesh of this leg was eaten for food and not for a ritual." She now wants to compare the sections with other remains in order to further investigate the thesis.

But the question of why is controversial. "It's hard to say whether this was food intake or a more complex cultural activity, such as for ritual purposes," paleoanthropologist Michael Petraglia, of Griffith University in Brisbane, who was not involved in the new study, told National Geographic.

Other scenarios possible

Because there are also other explanations – and whether it was cannibalism by definition remains open. According to Pobiner, this presupposes that perpetrators and victims belong to the same species. The shin bone that has now been analyzed was first identified as Australopithecus boisei and then as Homo erectus in 1990. In the meantime, however, it is said that it is clear that the remains cannot be clearly assigned to any particular hominin species. The use of stone tools also does not allow any conclusions to be drawn about this.

The chronological sequence of the damage is also uncertain: a big cat could have killed the hominin before others took over the remains.

Silvia Bello, a scientist at the Natural History Museum in London, who was not involved in the study, nevertheless considers the current study to be significant. The find suggests "that cannibalism may have been practiced at least occasionally long ago in the history of our ancestors," CNN quotes him as saying. Evidence of this behavior has also been found at other archaeological sites.

"This new evidence looks quite convincing and adds to the evidence of cannibalism in very early humans as well as the considerable evidence from later humans," Chris Stringer, principal investigator of human origins at London's Natural History Museum, told CNN. Whether this is the oldest clue – that also remains unclear for the time being. The shin is probably not the oldest known example, according to Stringer. On the cheekbone of a hominin fossil found in South Africa in 2000, which could be about 2 million years old, cut marks were also found.

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