Graves, engravings, and tools? Oh my!

 

Before we get started, I thought it would be good to recap the last decade of work.  If you'd like to skip straight to the current stuff, scroll down to the paragraph that begins "Yesterday, we got two more big announcements...."  First, I'll set the stage.

In 2013, explorers working on the suggestion of Lee Berger discovered a cache of hominin bones in an extremely remote chamber of the Rising Star Cave system in South Africa.  In 2015, the new hominin was introduced to the world by a set of papers, scans, and a documentary film.  The researchers suggested that this newly-described hominin was deliberately placing bodies of its contemporaries in the chamber, which at the time they termed "body disposal."  This suggestion sparked some skeptical remarks from folks like Chris Stringer, who thought that something with a brain that small could not engage in such a complex behavior.

I got involved almost immediately by trying to discern whether Homo naledi should be included in the human created kind.  My previous research seemed to demonstrate a consistent group of hominins that were closely similar to modern humans based on our skull and teeth characteristics.  My results indicated that H. naledi indeed was part of that human group, which then to my mind made the "body disposal" interpretation very consistent.

Last winter, Berger announced evidence of fire throughout the Rising Star Cave system.  I was pretty excited at the time, since fire would be a necessity for navigating the dark recesses of the cave where the remains were found.  I also expected some kind of scientific report detailing these discoveries, and now more than six months later, we're all still waiting for that report.  This has dampened my enthusiasm.  Berger continues to suggest that his lecture on the subject is the same as a preprint, which I find absurd.  Preprints contain (or should contain) all the details of a scientific paper, including measurements, diagrams, photographs, and the like.  His lecture is at best a press release, and I do not like publishing by press release.  That said, based on his Twitter feed, Berger seems just as frustrated at the lack of progress on his fire paper as the rest of us.  It's apparently an unusually slow review process.

Yesterday, we got two more big announcements from Berger at the Richard Leakey Memorial Symposium at Stony Brook.  This time, he presented clearer evidence of deliberate burial and newly discovered engravings in the chamber where the most bones have been found.  The announcement was accompanied by three papers that are already in review at eLife.  With their new publication model, that means they will be published in a possibly revised form.

The three papers are:

Remember these preprints are open access, and as always, I encourage you to read them for yourself and don't take my word for it.

Having read them all, I noticed that they read more like field reports than research papers.  These papers document what they've discovered, but there's a lot more experiments and work left to do.  I think one paper succeeds in meeting what I think would be the minimal requirements to make their case.  I'm not sure about the other one.  The shorter commentary article by Fuentes et al. depends heavily on what you think of this latest batch of papers.

Let's start with the burial evidence, which I think is convincing.  They report at least three different "features" that contain mostly the bones of one individual in a limited area where the sediments have been disturbed and in which the bones are preserved in peculiar orientations that would require some kind of sediment support during decomposition.  In one of the features, they describe an oval shaped mass of sediment with bones oriented vertically close to the edge of the feature.  That would make sense if there was a depression in the sediment into which a body was deposited and then covered over.  Otherwise, the bones would fall into more horizontal orientations during decomposition if the body was not support by surrounding sediments.  Surrounding at least one of these features, they find mostly empty sediments, which places the bones in one limited region, where the sediments are disturbed.  The bones themselves appear to be largely from one individual. So we have the remains of a single skeleton in a limited area, with no bones around it, with disturbed sediments, and with bones in orientations that could only be achieved by being covered over with sediments.  This is essentially the sort of evidence we have for various Neandertal burials, such as La Chapelle-aux-Saints.  It's not of the same overwhelming quality as Homo sapiens graves filled with grave goods and designated with a grave marker, but as far as ancient hominin burials go, this evidence from Rising Star is as good as or better than most claimed Neandertal burials and certainly better than anything we have from Homo erectus (which creationists like me also accept as human).

Another feature that the authors interpret as a burial contained a rock quite close to the hand of the skeleton.  The rock looks suspiciously like something shaped like a tool.  The paper refers to it as an artifact, but I'm not convinced that's appropriate.  It certainly could be a tool, and frankly that seems very likely.  But that entire feature, bones and all, was excavated as three blocks of sediment and visualized by synchrotron X-ray scanning.  According to the paper, the block of sediment has not been further excavated, and the rock remains sealed inside the field jacket.  The only images we have of it come from the scans.  Granted, they are extremely high resolution scans, but they are not the rock itself.  But it sure looks like a deliberately-shaped tool left in the hand of a skeleton.

The engravings described in the second paper are another issue altogether.  They were found in the antechamber on a pillar of rock leading into the Dinaledi Chamber where most of the original bones were excavated back in 2013-14.  Based on the evidence presented, there's no question that these are deliberate engravings.  They're crisscrossed lines that have been rubbed with some other type of sediment that gives them a distinctive color.  They resemble markings from other hominins like the Neandertal markings of Gorham's Cave in Gibraltar.

The problem is definitively linking the engravings to Homo naledi.  Despite the dates in the title of the paper, there was no dating of the engravings.  (If I were a reviewer, I'd make them rename the paper without the dates, which are not a finding of their research.)  There were no chemical analyses of the engravings.  This is very much a field report.  They took high resolution pictures under various lighting, made measurements of the engravings, and that was that.  They're unquestionably engravings, but who made them?

The same sorts of problems arise when we consider cultural evidences from other contexts, though.  In particular, our growing knowledge of Neandertal culture has grown from contextual clues rather than materials found in direct proximity to Neandertal remains.  But when we do find Neandertal bones in proximity to Mousterian tools and the remains of hearths, we do not doubt that the Neandertals made the tools and started the fires.

So the Rising Star engravings are not conclusive by a long shot, but when considered as a full package, the evidence of Homo naledi culture makes a compelling case in my view.  In Rising Star, we have evidence of graves, art, fire, and a possible stone tool all found in a cave that gives evidence of only one hominin exploring and occupying those deep underground spaces.  The simplest explanation would link the cultural remains directly with the hominin bones present.  Homo naledi made the fires, tools, art, and buried their dead in graves.  That's the conclusion of the Fuentes et al. paper, but again, the engravings are not definitively linked to Homo naledi.  And the fire?  We still don't have any description of the fire evidence, even though it sounds tantalizing.  But to argue that someone else made the fires or carved those lines introduces ad hoc hypotheses of cave intruders for which we have no other evidence (yet reported).  The simplest explanation is that the hominin buried under the engravings next to the hearths is the one who made them both.

As a creationist, I see this all fitting together in a very good case for Homo naledi's humanity.  These are the sorts of behaviors that I would expect from human beings, and they make sense.  Indirect they may be, but these evidences are the same sort of evidences I use to argue for the humanity of Neandertals.  I definitely want more.  I want to see that rock in the skeleton's hand.  I want to see chemical studies of the engravings.  I want to know if there are more, and maybe even clearer, Homo naledi graves.

For now, I'll just have to be cautiously optimistic.

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.


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