“Fossil First: Ancient Human Relative May Have Buried Its Dead” (Reuters). “Why Did Homo naledi Bury Its Dead?” (NOVA Next). These are just two of the many hyped headlines that appeared last September in response to a paper purporting the discovery, in a cave in South Africa, of a new species by paleoanthropologist Lee R. Berger of the University of the Witwatersrand, Johannesburg. There were reasons for skepticism from the get-go.

The age of the fossils is undetermined, and it is not yet known where in the hominin lineage the fossils fit. Their hands, wrists and feet are similar to small modern humans, and their brain volume is closer to that of the small-brained australopithecines, like Lucy. Researchers are debating whether these and other traits constitute a new species or a variation on an existing species. Instead of publishing in Science or Nature, the prestigious journals in which major new fossil human finds are typically announced, the authors unveiled their discovery in eLIFE (elifesciences.org/content/4/e09561), an open-access online journal that fast-tracks the peer-review process. And instead of meticulously sorting through the 1,550 fossils (belonging to at least 15 individuals) for many years, as is common in paleoanthropology, the analysis was published a mere year and a half after their discovery in November 2013 and March 2014.*

What triggered my skepticism, however, was the scientists' conjecture that the site represents an example of “deliberate body disposal,” which, as the media read between the lines, implies an intentional burial procedure. This, they concluded was the likeliest explanation compared with four other hypotheses.

Occupation. There is no debris in the chamber, which is so dark that habitation would have required artificial light, for which there is no evidence, and the cave is nearly inaccessible and appears never to have had easy access. Water transport. Caves that have been inundated show sedimentological layers of coarse-grained material, which is lacking in the Dinaledi Chamber, where the specimens were uncovered. Predators. There are no signs of predation on the skeletal remains and no fossils from predators. Death trap. The sedimentary remains indicate that the fossils were deposited over a span of time, so that rules out a single calamitous event, and the near unreachability of the chamber makes attritional individual entry and death unlikely.

Finally, the ages of the 13 individuals so identified—three infants, three young juveniles, one old juvenile, one subadult, four young adults and one old adult—are unlike those of other cave deposits for which cause of death and deposition have been determined. It's a riddle, wrapped in sediment, inside a grotto.

While the authors had given it consideration, I believe they are downplaying an all too common cause of death in our ancestors—homicide in the form of war, murder or sacrifice. Lawrence H. Keeley, in War Before Civilization (1996), and Steven A. LeBlanc, in Constant Battles (2003), review hundreds of archaeological studies showing that significant percentages of ancestral people died violently. In his 2011 book The Better Angels of Our Nature, Steven Pinker aggregates a data set of 21 archaeological sites to show a violent death rate of about 15 percent. In a 2013 paper in the journal Science, Douglas P. Fry and Patrik Söderberg dispute the theory that war was prevalent in ancient humans by claiming that of the 148 episodes of violence in 21 mobile foraging bands, more than half “were perpetrated by lone individuals, and almost two-thirds resulted from accidents, interfamilial disputes, within-group executions, or interpersonal motives such as competition over a particular woman.”*

Whatever you call it—war or murder—it is violent death nonetheless, and further examination of the Homo naledi fossils should again consider violence (war or murder for the adults, sacrifice for the juveniles) as a plausible cause of death and deposition in the cave. Recall that after 5,000-year-old Ötzi the Iceman was discovered in a melting glacier in the Ötztal Alps in the Tyrol in 1991, it took a decade before archaeologists determined that he died violently, after he killed at least two other people in what appears to have been a clash between hunting parties. It's a side of our nature we are reluctant to admit, but consider it we must when confronted with dead bodies in dark places.*

*Editor's Note (1/7/16): The asterisked paragraphs from the print article were edited after posting. The originals incorrectly stated that because the age of the recently reported Homo naledi fossils have not yet been determined, it is impossible to conclude where they fit in the hominin lineage. But only morphological features are necessary to determine a fossil's taxonomic group. Additionally, the original wording suggested that further examination of the fossils should consider violence as a potential cause of death but failed to note that signs of violence had been considered in the initial study.