Ancient human relatives may have been cannibals 1.45 million years ago

A butchered hominin fossil suggests our ancestors had a dark past.

A 1.45-million-year-old shin bone discovered in northern Kenya has revealed a disturbing possibility about human evolution: our ancient relatives may have been eating one another hundreds of thousands of years before modern humans appeared.

In a study published in June 2023, scientists led by paleoanthropologist Briana Pobiner of the Smithsonian’s National Museum of Natural History identified nine marks on the fossil that closely resemble cuts made by sharp stone tools. The findings provide some of the oldest compelling evidence that early hominins butchered members of their own evolutionary family.

Whether the flesh was actually eaten, however, is another question.

“The information we have tells us that hominins were likely eating other hominins at least 1.45 million years ago,” she said when the study was published.

A dark past

While cannibalism is not uncommon among various species, evidence that our distant evolutionary relatives consumed one another is relatively rare and often contested.

The fossil at the center of the research, known as KNM-ER 741, was discovered by Mary Leakey in 1970 and preserved in the collections of the National Museums of Kenya. Pobiner examined it in 2017 while searching for evidence of ancient predators.

Instead of the tooth marks she expected, she spotted a series of narrow grooves that looked suspiciously like the traces left by stone tools.

Determined to confirm her hypothesis, Pobiner collaborated with Michael Pante of Colorado State University and Trevor Keevil, then at Purdue University. By creating 3D scans of molds made from the bone’s cut marks, they compared them to a comprehensive database of 898 experimentally produced tooth, butchery, and trample marks.

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Their analysis revealed that nine of the eleven marks were indisputably the result of stone tool usage. The remaining two marks appeared to be bite marks, potentially originating from a large cat, with a lion being the closest match. These bite marks could have come from one of the three species of saber-tooth cats that roamed the landscape at that time.

While the cut marks alone do not conclusively prove that the leg and other body parts were consumed, it is the most likely scenario. The location of the cut marks on the bone, where the calf muscle would have been attached, indicates a deliberate attempt to remove flesh.

Furthermore, the uniform orientation of the marks suggests that a stone tool-wielding hand could have made them successively, without changing grip or adjusting the angle of attack. These cut marks are virtually indistinguishable from those found on animal fossils processed for consumption, implying that this possible episode of butchery may have been associated with obtaining food rather than a ritual.

But not everyone agreed that the evidence established cannibalism. Archaeologists interviewed by Science News in 2023, when the study was first released, cautioned that cutting flesh from a body does not necessarily mean it was eaten. Such marks could also result from other forms of bodily processing, including practices whose purpose is impossible to reconstruct from a single fossil.

The fossil was initially assigned to Australopithecus boisei, now generally called Paranthropus boisei, and was later attributed to Homo erectus. However, scientists still cannot confidently determine which species the fossil belongs to.

Cannibalism or something even more sinister?

It is unclear who was eaten and who did the eating. Cannibalism, by definition, requires both parties to belong to the same species. Without further evidence, it is challenging to definitively classify this behavior as cannibalistic.

The alternative, which is perhaps even wilder, is that different species within the hominin family might have engaged in interspecies consumption.

But what about the big cat bite marks? The person performing the butchery could have removed most of the meat from the leg bone before a big cat scavenged the remains. Or perhaps a big cat may have killed a hominin before being scared away, allowing opportunistic hominins to claim the kill. The precise sequence of events remains an enigma, shrouded in predatory intrigue.

The discovery also cannot tell us whether the animal or hominin responsible for the cuts was starving, scavenging opportunistically, or acting for some other reason.

New clues from another ancient human species

More recent discoveries have added to the evidence that cannibalism was sometimes part of life among ancient human relatives.

In July 2026, researchers working at Gran Dolina in Spain announced the recovery of 24 additional fossils belonging to Homo antecessor, a human relative that lived around 850,000 years ago. The discoveries increased the minimum number of individuals represented at the site to between 13 and 15, including at least six adults.

Many of the newly recovered bones bore cut marks associated with the processing of bodies. Earlier discoveries had already established Gran Dolina as an important site for studying prehistoric cannibalism, but the remains were dominated by infants and juveniles. The new adult fossils indicate that the practice was not restricted to younger individuals.

The Spanish findings are much younger than the Kenyan shin bone and do not prove that its owner was eaten. Nevertheless, they provide a richer picture of the ways ancient humans could process the remains of other members of their species.

But we still don’t have a definitive answer about what happened to KNM-ER 741.

Whatever happened in northern Kenya 1.45 million years ago, the fossil is an extraordinary reminder that the behavior of our earliest relatives was often more complicated than the scattered bones they left behind can reveal.

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The findings appeared in the journal Scientific Reports.

Updated November 2, 2026: This article was originally published in June 2023. It has been revised to clarify the evidence for possible prehistoric cannibalism, incorporate subsequent discoveries involving ancient human relatives, and discuss new methods for identifying butchery marks on fossil bones. This is part of ZME Science’s ongoing efforts to revisit past reporting, incorporate new scientific findings, and ensure our articles remain accurate, relevant, and up to date as research evolves.