Survival of the Grisliest: 1.45 Million-Year-Old Bone Reveals Cannibalistic Behavior Among Early Humans

New findings indicate that our early human relatives may have been practicing cannibalism 1.45 million years ago. The tell-tale cut marks on a fossilized leg bone bring light to the ancient survival strategies of our evolutionary kin.

Scientists from the Smithsonian’s National Museum of Natural History have made a shocking discovery regarding the earliest conclusive evidence of our close evolutionary relatives engaging in cannibalism.

The findings, published today in Scientific Reports, reveal the identification of nine distinct cut marks on a 1.45 million-year-old shin bone belonging to a Homo sapiens relative found in northern Kenya. Advanced analysis using 3D models of the fossil’s surface has confirmed that these cut marks were undeniably caused by stone tools.

This remarkable revelation represents the oldest known occurrence of such behavior, supported by a high level of confidence and specificity.

Briana Pobiner, a paleoanthropologist at the National Museum of Natural History and co-author of the study explains, “The information we have tells us that hominins were likely eating other hominins at least 1.45 million years ago.

“There are numerous other examples of species from the human evolutionary tree consuming each other for nutrition, but this fossil suggests that our species’ relatives were eating each other to survive further into the past than we recognized.”

While searching for clues about ancient predators that may have hunted and consumed our human ancestors, Briana Pobiner, during her examination of the collections at the Nairobi National Museum of the National Museums of Kenya, came across a fossilized tibia, or shin bone. Utilizing a handheld magnifying lens, she scrutinized the bone in search of bite marks left by extinct creatures. Surprisingly, she immediately noticed what appeared to be clear indications of butchery.

To determine whether the marks on the surface of the fossil were indeed cut marks, Pobiner sent molds of the cuts to Michael Pante, a co-author from Colorado State University. These molds were created using the same material employed by dentists to produce teeth impressions. Pobiner did not provide Pante with any specific information, simply requesting him to analyze the marks on the molds and identify their origins. Pante generated 3D scans of the molds and compared the shape of the marks with a comprehensive database containing 898 distinct tooth, butchery, and trample marks obtained through controlled experiments.

The analysis yielded definitive results, positively identifying nine out of the 11 marks as matching the pattern of damage inflicted by stone tools. The remaining two marks were likely bite marks from a large feline predator, with a lion being the closest match. According to Pobiner, these bite marks could have originated from one of three different species of saber-toothed cats that roamed the landscape during the time when the owner of the shin bone was alive.

Although the cut marks alone do not prove that the human relative responsible also consumed the leg, Pobiner suggests that this is the most plausible scenario. She explains that the cut marks are situated at the attachment point of a calf muscle—a prime location for removing the flesh. Furthermore, all the cut marks exhibit the same orientation, indicating that a hand wielding a stone tool could have produced them in succession without adjusting the grip or altering the angle of attack.

“These cut marks look very similar to what I’ve seen on animal fossils that were being processed for consumption,” Pobiner added. “It seems most likely that the meat from this leg was eaten and that it was eaten for nutrition as opposed to for a ritual.”

While the evidence may suggest cannibalism at first glance, Briana Pobiner explains that there is insufficient information to definitively determine this, as cannibalism requires the eater and the eaten to belong to the same species.

Initially identified as Australopithecus boisei and later as Homo erectus in 1990, experts now agree that the specimen cannot be assigned to a specific hominin species due to the limited available data. Additionally, the use of stone tools does not provide a clear indication of which species might have been responsible for the butchery. Recent research by Rick Potts, the National Museum of Natural History’s Peter Buck Chair of Human Origins, has challenged the previous assumption that only the Homo genus made and utilized stone tools.

Hence, the fossil could potentially represent prehistoric cannibalism, but it is also plausible that it reflects one species consuming its evolutionary cousin.

The stone tool cut marks do not overlap with the two bite marks, making it difficult to infer the sequence of events. For example, it is possible that after the hominins removed most of the meat from the leg bone, a large feline scavenged the remains. Alternatively, a big cat may have killed a hapless hominin and then fled or was driven away before opportunistic hominins took advantage of the kill.

Another fossil, a skull discovered in South Africa in 1976, has previously sparked debates regarding the earliest known evidence of human relatives engaging in cannibalism. The age estimates for this skull range from 1.5 to 2.6 million years old. However, two studies examining the fossil (one published in 2000 and the other in 2018) disagree on the origin of marks below the skull’s right cheekbone.

One study suggests that the marks resulted from stone tools used by hominin relatives, while the other argues that they were formed by contact with sharp-edged stone blocks resting against the skull. Moreover, even if ancient hominins created the marks, it remains unclear whether they were involved in butchering each other for food, given the absence of significant muscle groups on the skull.

To resolve the question of whether the studied fossil tibia is indeed the oldest cut-marked hominin specimen, Pobiner expresses her desire to reexamine the skull from South Africa, which purportedly exhibits similar cut marks as observed in the present study.

She also emphasizes that this astonishing new discovery underscores the value of museum collections.

Source: 10.1038/s41598-023-35702-7

Image Credit: Getty & JENNIFER CLARK