According to a new study, a 1.45 million-year-old hominid leg fossil contains evidence of butchering and possibly eating one another.
The fossil, which is a shin and knee joint, has nine incisions, made by an ancient person with a stone instrument. Researchers report on June 26 in Scientific Reports that 3-D models of these scars resemble damage created by stone tools rather than large predators' bites or by animal trampling.
According to paleoanthropologist Briana Pobiner of the Smithsonian Institution in Washington, D.C., those incisions are the earliest credible example of such butchery and possibly cannibalism among archaic hominids. However, that meaning is contested.
While researching fossils at the Nairobi National Museum in Kenya, Pobiner first saw the incised leg bone. She was curious as to what animals, if any, had preyed on and eaten our early hominid ancestors. But the marks on the bone of her leg gave the impression of having been butchered.
Paleoanthropologists Michael Pante from Colorado State University in Fort Collins and Trevor Keevil from Purdue University in West Lafayette, Indiana were sent casts of 11 incisions on the fossil by Pobiner. Using 3-D scanners, the two compared the bone marks to 898 other types of marks found nearby, such as those left by stone tools, pounding stones, crocodile and lion teeth, and cow hooves (SN: 11/6/17).
Pobiner claims that nine of the scars are consistent with damage caused by primitive tools. The other two scars were caused by a large cat's bite, possibly a saber-toothed one.
The old leg fossil has not been positively identified as to what species it belonged to. Pobiner and coworkers speculate that it could be an example of Homo erectus, Homo habilis, or perhaps the small-brained species Paranthropus boisei. Stone tool marks on the leg fossil cannot be used to determine whether they were made by a member of the same or a distinct hominin species.
Pobiner says the fossil shows cuts associated with the removal of a portion of flesh around where a calf muscle joined to bone. With only a single, broken bone in hand, the motivations for that conduct are still unclear. Pobiner speculates that whichever hominin left the cut marks was hungry and only wanted to remove the meat from the bone.
Raphael Hanon, a zooarchaeologist at Wits University in Johannesburg, confirms this. According to Hanon, who was not a part of Pobiner's team, slicing into the meaty area of a lower thigh likely represented a desire for food rather than a ritual performance of some type. He says there's no telling if other, meatier sections of the body, such the shoulder and upper leg, were stripped bare as well.
However, zooarchaeologist Palmira Saladié from the Catalan Institute of Human Paleoecology and Social Evolution in Tarragona, Spain, argues that the incisions made by a stone tool on a fragment of a thigh bone do not provide sufficient evidence to decide whether hunger motivated flesh removal. Saladié adds that Pobiner's results may reflect scenarios like cannibalism as a means of supplementing other food sources, a ritual practice that did not involve cannibalism, or the consumption of a defeated adversary after a struggle between communities.
Even according to Yonatan Sahle, an archaeologist at the University of Cape Town in South Africa, the meaning is still unclear. Cannibalism in the Stone Age is possible, but "the present evidence is not strong enough to enable such an inference," he writes.
The fact that the leg fossil's initial setting is a mystery does not help matters. It had broken free from the surrounding sediment and was discovered lying on the ground at a place in northern Kenya. The location of the fossil directly above a layer of volcanic ash that has been dated to between 1.5 and 1.6 million years old provides the basis for this age estimate. Since the ash layer is older than the silt where the leg bone was found, scientists have assumed that the bone was initially deposited.
Discussion was also sparked by a possibly earlier occurrence of a slaughtered hominid that was reported in 2000. An upper jaw was discovered at a site in South Africa, with estimates of its age between 1.5 and 2.6 million years ago. The incisions on the jaw were characterized as having been made by cutting through a muscle to remove the lower jaw. However, Hanon and coworkers have proposed that the incisions could have been caused by animal trampling or inadvertent rubbing of the fossil against sharp rocks before it was excavated.
Hanon claims that nine out of the eleven incisions found on the hominid leg fossil were not caused by such forces, praising the work of Pobiner's team. He thinks that the ancient markings had a "very high probability" of having been made by a hominid with a stone instrument.
Tim White, a paleoanthropologist at the University of California, Berkeley, who has long researched skeletal indications to cannibalism, argues that even if subsequent research improves that possibility, such evidence falls well short of showing butchery or cannibalism (SN: 1/2/93). White says the fossil found in Kenya "an interesting scientific curiosity that changes nothing of significance."
CITATIONS
B. Pobiner, M. Pante and T. Keevil. Early Pleistocene cut marked hominin fossil from Koobi Fora, Kenya. Scientific Reports. Published June 26, 2023. doi: 10.1038/s41598-023-35702-7.
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