To be human is to grapple with death. Anthropologists are particularly interested in ancient death rituals because they show our ancestors acknowledged that, yeah, people are going to die one day. By studying these rituals in ancient humans and other hominins, scientists believe we can come to understand the evolution of the human condition. To do so, as researchers pointed out in Proceedings of the National Academy of Sciences on Monday, it’s crucial to figure out what is — and what isn’t — a death ritual.

In the study, a team of international researchers offers a CSI-style fact-check of two sites thought to show evidence of ritual burials, with galaxy-brain implications. The two sites, where huge assemblages of hominin bones have been found, were most likely not where ancient death rituals were performed, they argue. Instead, the placement of these bones shows evidence of a much more gruesome phenomenon: a run-in with carnivores.

“A ‘central aspect’ of the human condition is our capacity to anticipate our own death, and thus, ponder the significance of mortality across time and space,” the researchers write. “If these sites were actually scenes of ancient mortuary behavior then there would be an implication that ‘humans had developed a sense of mortal transience by approximately 600,000 to 300,000 years ago.’”

But that’s not what this team found.

baboon skull
A side view of a baboon cranium, one of the comparative assemblages the authors used in the analysis.

Their study focused on the bones in the caves of Spain’s Sima de los Huesos and South Africa’s Dinaledi Chamber, both of which are considered by some scientists to be burial ritual sites. Spanish for “pit of bones,” the former was first found in the 1970s and is considered one of the richest hominin fossil sites in the world — containing both Homo heidelbergensis and early Neanderthals. The latter, the Dinaledi Chamber, is part the Rising Star cave system in South Africa and was where fossils of the human ancestor Homo naledi were found in 2015.

Because no signs of tools or food have been found with these bones, some scientists have hypothesized that the hominin remains were thrown into the pit as a kind of ritual. Some scientists have also argued that these bones also don’t show any damage suggesting that predatory carnivores were involved. Yet, the proportions of bone fragments found there are a bit weird for a supposed burial site. The authors argue they both show a “paucity” of axial bones (the head and neck bones) and the marrow-filled rounded ends of long bones — a strange discontinuity suggesting that a re-evaluation is in order.

To find out the truth about how these hominins died, the researchers applied a machine learning approach to the fossil remains at these sites, both of which were dated to the Middle Pleistocene, about 781,000 to 126,000 years ago.

Dinaledi Chamber, South Africa
An illustration of the Dinaledi Chamber.

Using spatial details about the burial site fossils to previously published data on 14 other modern and prehistoric accumulations of archaic human, modern human, and nonhuman primate remains, they set up their algorithm to cluster the burial site bones into categories, including hominin burial sitessss, undisturbed human corpses, scavenged human corpses, and “leopard-consumed baboons.”

When it came down to what sort of assemblage these bones resembled most, it wasn’t a meaningful, ancient burial ritual like the sort found in other locations — rather, it was a run-in with carnivores.

The skeletal remains, the researchers write, “did not find their way into the cave chamber as complete skeletons.” They note that “while other taphonomic factors may have been at play, we consider the feeding activities of carnivores to be a likely source of this disturbance.”

Of course, they’re careful to note that this finding doesn’t rule out the possibility that ancient burials did occur. This unexpected finding just means that there’s a need to further analyze the sites where burial practices are assumed to have taken place. Sometimes remains indicate rituals designed to define the human condition; other times, they’re just a sad pile of bones.