Did Homo naledi really bury their own dead?
|A modern human cemetery at Glendalough.|
After my piece last week on the brain of Homo naledi, I was reminded of the recent paper in PNAS describing the classification of hominin "burial" sites. Since that paper casts some doubt on the conclusion that Homo naledi buried their own dead, I suppose I would be remiss to not share a few comments and thoughts.
First of all, the paper by Egeland and colleagues provides a "machine learning" approach to classifying accumulations of hominin bones. Their objective was to evaluate claims that certain hominin sites represent deliberate burial (strictly in the sense of body disposal, without any of the mortuary symbolism that would accompany modern human burial). The idea behind the analysis is to give a computer various characteristics of these bone sites and train the computer to recognize burials. Their results showed that modern human burial sites were recognized by the computer as distinct from accumulation of bones due to predators (like leopards eating baboons) or scavenging. So far, so good.
Also included in their sample of hominin bone sites were three very interesting locations: Sima de los Huesos ("Pit of Bones") in Spain, Skhul (a modern human burial site) in northern Israel, and the Dinaledi chamber (where Homo naledi was originally discovered) in South Africa. The Skhul site is notable as one where a purportedly symbolic item was buried with two of the bodies: The jawbone of a pig was buried with skeleton Skhul V and a bovine skull with Skhul IX. Egeland and colleagues included Skhul V in their sample, but it grouped with the "Leopard Refuse" site and separately from the undisturbed modern human burials. That's odd, since I understand Skhul is accepted as an example of an intentional burial site.
Sima de los Huesos is a remarkable site in north central Spain, representing the remains of a deep pit into which hominin bones accumulated. With more than 5,500 skeletal elements recovered from at least 28 individuals, Sima has turned out to be one of the richest hominin fossil sites in the world (although Rising Star and Homo naledi will surely challenge that title). Recently, DNA testing of one of the bones matched DNA from other known Neandertals. The surprising concentration of bodies in this pit, along with the presence of a hand ax, led researchers to suggest that it was a deliberate burial site, where bodies were dropped into the ground. In the clustering results of Egeland and colleagues, Sima de los Huesos clustered together with the Dinaledi chamber, a sample of modern human remains that had been scavenged, and a site called Misgrot Cave from South Africa, which appears to be a mass mortality site of baboons.
Based on these findings, Egeland and colleagues conclude
Our results indicate that nonanthropogenic agents and abiotic processes cannot yet be ruled out as significant contributors to the ultimate condition of both collections [Sima (SH) and Dinaledi (DC)]. This finding does not falsify hypotheses of deliberate disposal for the SH and DC corpses, but does indicate that the data also support partially or completely nonanthropogenic formational histories.Let me see if I can translate this: They acknowledge that their findings do not falsify deliberate burial, but they say that other explanations cannot be ruled out either. Those other explanations are burial followed by some kind of disturbance or accumulation of bones by some other means (predators, mass death, etc.). So in other words, their study can't rule out any explanation for how the bones got there. Interesting.
Let's think again about the context of the Dinaledi chamber, which lies at the end of an hours-long journey underground in the complete dark zone of a cave at the bottom of a 39-foot tall chute that is on average 8 inches wide. In that chamber are almost nothing but Homo naledi bones, many of which are still in articulated pieces. The preservation is virtually unprecedented, as indicated by some of the impossibly small bones discovered.
So I find myself frowning with great skepticism when Egeland and colleagues seriously entertain the possibility of predators messing with the bones in the Dinaledi Chamber. Given the context, I think we can take that right off the table. It's extremely unlikely that a predator or predators would go that far back into a dark cave with that many bodies of heavy hominins. It would have to be a really large predator, and how could it get down into the Dinaledi Chamber and then back out again? On the other hand, if we want to entertain the possibility that predators messed with the bones before they were deposited, then how did the bones get down there? And how did they get their in large articulated chunks, like complete hands? This really stretches my imagination to the breaking point.AFAIK this Homo naledi flexor hallucis brevis sesamoid is the only one in the hominin fossil record. I was only able to ID it in a sediment bag bc of @BeccaPeixotto @EFeuerriegel @AGurtov @Paleo_Bonegirl @hanboo28 & Marina's exquisitely meticulous work in the Dinaledi Chamber! pic.twitter.com/yrQYmEQ7kH— Zach Throckmorton (@throckman) May 15, 2018
The other possibility suggested by the analysis of Egeland and colleagues is that the Dinaledi chamber is a burial site that has been disturbed in some other way, which is actually something suggested from the beginning. Lee Berger's team originally proposed that the bodies had been disturbed multiple times as the water level rose and fell in the chamber. Burial would account for the strange concentration of so many individuals and so many bones in such an inaccessible location, and water disturbance would explain how the bodies became damaged and disarticulated but in a way that keeps substantial body parts (arms, legs, pieces of torsos) together. So I'm not really surprised that Egeland and colleagues found that the Dinaledi Chamber did not look like modern undisturbed human burials, since I don't think anyone ever suggested that they would.
I remain confident that Homo naledi will turn out to be fully human, descended from Adam through Noah, and made in the image and likeness of God. At the end of time, when we gather around the throne of God in a multitude from every people, tribe, nation, and language, I hope I'll see some of them there. Despite the work of Egeland and colleagues, I think the burial evidence, as well as multiple baraminology studies of hominins and the recent discoveries about the brain of Homo naledi, supports my understanding of Homo naledi as human.
But if I'm wrong, that's OK too. I find it hard to imagine alternative scenarios to explain Homo naledi, but my imagination is not the measuring rod of what is or is not true. What I can be certain about is that creationists currently disagree about Homo naledi, so I think we should all be very suspicious of anyone who says that the mystery of Homo naledi has been definitively and finally solved.
The most exciting thing about Homo naledi is that excavation and fossil discovery is still going on. Last I heard there were three different locations of Homo naledi bones in the Rising Star Cave. There will be Homo naledi discoveries to last a lifetime. Who knows what the researchers will discover? In the mean time, I hope all creationists will be gracious and generous with each other while the data continue to roll in and we learn more about this fascinating hominin.
Feedback? Email me at toddcharleswood [at] gmail [dot] com. If you enjoyed this article, please consider a contribution to Core Academy of Science. Thank you.