View of the hominin tibia and magnified area that shows cut marks. Scale = 4 cm. In a new study published today, June 26, in Scientific Reports, Smithsonian’s National Museum of Natural History paleoanthropologist Briana Pobiner and her co-authors describe nine cut marks on a 1.45 million-year-old left shin bone from a relative of Homo sapiens found in northern Kenya. Analysis of 3D models of the fossil’s surface revealed that the cut marks were dead ringers for the damage inflicted by stone tools. This is the oldest instance of this behavior known with a high degree of confidence and specificity. Pobiner first encountered the fossilized tibia, or shin bone, in the collections of the National Museums of Kenya’s Nairobi National Museum while looking for clues about which prehistoric predators might have been hunting and eating humans’ ancient relatives. With a handheld magnifying lens, Pobiner pored over the tibia looking for bite marks from extinct beasts when she instead noticed what immediately looked to her like evidence of butchery. “You can make some pretty amazing discoveries by going back into museum collections and taking a second look at fossils,” Pobiner said. “Not everyone sees everything the first time around. It takes a community of scientists coming in with different questions and techniques to keep expanding our knowledge of the world.”
Newswise — Scientists from the Smithsonian's National Museum of Natural History have made a groundbreaking discovery, uncovering the earliest indisputable proof of human ancestors engaging in cannibalistic behavior, specifically the act of butchering and potentially consuming one another.
In a recent publication on June 26, researchers, including paleoanthropologist Briana Pobiner from the National Museum of Natural History, unveiled a groundbreaking study in Scientific Reports. The study highlights the discovery of nine distinct cut marks on the left shin bone of a human ancestor, estimated to be around 1.45 million years old, discovered in northern Kenya. Utilizing advanced 3D modeling techniques, the team confirmed that these cut marks bore a striking resemblance to the characteristic damage caused by ancient stone tools. This remarkable finding represents the earliest and most definitive evidence to date of such behavior, showcasing an unparalleled level of confidence and specificity in our understanding of our ancestors' actions.
According to Pobiner, "Based on the available evidence, it appears that hominins were engaging in cannibalism as early as 1.45 million years ago." Pobiner further explains, "While there are previous instances of different species within the human evolutionary lineage resorting to cannibalism for sustenance, this particular fossil indicates that our ancestral relatives were practicing cannibalism even further back in history than we had previously acknowledged."
During her search for insights into the predators that may have preyed on our early ancestors, Pobiner stumbled upon the fossilized tibia (shin bone) in the archives of Nairobi National Museum, under the care of the National Museums of Kenya. Employing a handheld magnifying lens, Pobiner meticulously examined the tibia, seeking signs of bite marks left by long-extinct creatures. To her surprise, she quickly recognized what appeared to be unmistakable indications of butchery, diverging from her initial expectations.
In order to confirm whether the surface features observed on the fossil were indeed cut marks, Pobiner took proactive measures. She sent molds of the cuts, expertly crafted using dental impression material, to co-author Michael Pante from Colorado State University. Pobiner deliberately withheld any information about the source or nature of the molds, instructing Pante to analyze the marks and provide insights into their origin. Pante proceeded to generate 3D scans of the molds and meticulously compared the shape of the marks with a comprehensive database containing 898 distinct tooth marks, butchery marks, and trample marks, all derived from controlled experiments.
After a thorough analysis, the study confirmed that out of the 11 marks observed, nine were definitively identified as matching the characteristic damage caused by stone tools. The remaining two marks were determined to be probable bite marks inflicted by a large feline predator, with a lion being the closest match. Pobiner suggests that these bite marks could have originated from one of the three distinct types of saber-toothed cats that roamed the environment during the lifetime of the individual to whom the shin bone belonged.
While the cut marks alone cannot provide conclusive evidence that the human ancestor responsible for inflicting them also consumed the leg as a meal, Pobiner suggests that this scenario appears to be the most probable. Pobiner points out that the cut marks are precisely positioned where a calf muscle would have been attached to the bone, indicating that they were likely made with the intention of removing a portion of flesh. Furthermore, all the cut marks exhibit a consistent orientation, suggesting that they were made in rapid succession by a hand wielding a stone tool without the need to alter the grip or adjust the angle of attack. These observations support the hypothesis that the individual was engaged in butchery for the purpose of obtaining meat.
Pobiner remarks, "The resemblance of these cut marks to those found on animal fossils prepared for consumption is striking." She further states, "It appears highly probable that the meat from this particular leg was indeed consumed, and its consumption can be attributed to nutritional needs rather than ritualistic practices."
Pobiner clarifies that while this case might appear as cannibalism at first glance, there is currently insufficient evidence to definitively establish such a conclusion. Cannibalism, by definition, necessitates that both the consumer and the consumed belong to the same species.
Initially identified as Australopithecus boisei and later as Homo erectus in 1990, the fossilized shin bone's classification remains uncertain due to a lack of adequate information to attribute it to a specific hominin species. Additionally, the presence of stone tools does not provide sufficient evidence to narrow down the possible hominin species responsible for the butchery marks. Recent research conducted by Rick Potts, the Peter Buck Chair of Human Origins at the National Museum of Natural History, challenges the previously widespread assumption that stone tool production and usage were exclusive to a single genus, Homo. This further underscores the complexity and diversity within the hominin lineage and calls for a more nuanced understanding of the relationship between stone tools and various hominin species.
There is a potential interpretation for this fossil indicating prehistoric cannibalism, although it is equally plausible that it represents one species consuming its evolutionary relative.
Due to the absence of overlapping stone-tool cut marks and bite marks, it is challenging to determine the sequence of events with certainty. One possibility is that after hominins had already extracted most of the meat from the leg bone, a large cat could have scavenged the remains. Another scenario is that a big cat initially killed a hominin, but was then either chased away or quickly retreated, allowing opportunistic hominins to take control of the carcass.
The discovery of another fossil, a skull initially unearthed in South Africa in 1976, has been a subject of debate regarding a potential early case of human relatives engaging in cannibalistic behavior. The estimated age of this skull varies between 1.5 and 2.6 million years old, adding to its uncertainty. Two separate studies conducted on the fossil, one published in 2000 and the other in 2018, present conflicting viewpoints regarding the origin of marks located just below the skull's right cheekbone. While one study suggests that the marks were created by stone tools used by hominin relatives, the other proposes that they were caused by contact with sharp-edged stone blocks found near the skull. Furthermore, even if the marks were indeed made by ancient hominins, the absence of significant muscle groups on the skull makes it unclear whether the intent behind such actions was related to butchering for food.
In order to address the question of whether the fossil tibia studied by her and her colleagues is genuinely the oldest known hominin fossil with cut marks, Pobiner expressed her interest in reexamining the skull discovered in South Africa. This particular skull has been suggested to exhibit cut marks using similar techniques observed in the current study, and Pobiner is keen on further investigating this claim.
In addition, she emphasized that this groundbreaking discovery serves as compelling evidence for the immense value held within museum collections.
Pobiner highlighted the significance of revisiting museum collections and reexamining fossils, stating, "By delving back into museum collections and conducting a fresh analysis, remarkable discoveries can be made. Not everything is initially apparent to everyone. It requires a collaborative effort among scientists with diverse perspectives, questions, and methodologies to continually expand our understanding of the world."
This research was supported by funding from the Smithsonian, the Peter Buck Fund for Human Origins Research and Colorado State University.
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