Pre-human burial by Homo naledi challenged

Did ancient hominins carry out a burial? The lack of evidence for alternatives led many to conclude yes; but that evidence isn’t as clear cut as they think.


In 2015 palaeoanthropologists discovered what might be the oldest burial ever. A 2 milllion year old human relative carried its dead deep into a cave; disposing of them in a “burial chamber” that could only be reached by crawling through the pitch black.

The bones recovered from Homo naledi's burial chamber

The bones recovered from Homo naledi’s burial chamber

And if that’s not impressive enough for you: this was all done by a species with a chimp-sized brain called Homo naledi. They seem to have carried out these burials for thousands of years; indicating a long-lasting social structure like those seen in modern humans.

The fact that such a small-brained species performed this “modern” behaviour could rewrite our understanding of the filthy monkey men we evolved from. Unless, of course, they actually didn’t perform any burials.

A review of the evidence for Homo naledi‘s funeral parlour suggests they might not been deliberately burying their dead after all.

The evidence for burial

The main evidence for this ancient burial comes from the fact the initial discoverers ruled out pretty much every other cause. They worked for more than a year after the initial discovery, looking for evidence that something else was responsible. And they just couldn’t find it.

Malapa cave, where other human fossils accumulated through death traps

Malapa cave, where other human fossils accumulated through death traps

For example, there are other caves full of hominin bones from the time period (some of which can be found nearby). However, these accumulations were the result of “death traps.” These are creatively titled holes in the roof of the cave that animals fall through and die. Yet the Homo naledi burial site shows no evidence of such a hole in the roof. Additionally, death traps don’t tend to discriminate about who falls into them. So you wind up with a mixture of animals, humans, and everything in between. Yet only Homo naledi fossils were found at this burial site.

Another alternative is that a different species dragged the remains into the cave. Some predators will hide their prey away for later consumption. However, none of the examined bones had evidence of tooth marks; suggesting this didn’t happen. In fact, most of the damage done to the remains appears to have happened long after death; like bugs scratching the bones as they ate the rotting flesh.

Yet another explanation is that the remains were washed into the cave. But much like the death trap, this should wash  everything into the cave; not just Homo naledi. The researchers also observed that the sediment in the cave doesn’t look like something which would have accumulated as a result of water.

A cross section of Rising Star Cave, where Homo naledi was found

A cross section of Rising Star Cave, where Homo naledi was found. Note the lack of deathtraps

Birds against burials

All of this evidence seems rather impressive. Or rather, the lack of evidence for alternatives is impressive. Except for the fact it seems there’s so little data available for the site that these alternatives can’t actually be ruled out.

For example, evidence against carnivores being responsible includes the fact no bones with teeth marks are found. Yet the surface of only 1% of the fossils is intact. So there could be carnivore marks on 99% of the bones and we’d have no idea. Further, whilst thousands of fossils were recovered from the site each individual Homo naledi found had huge chunks missing. Again, think how much evidence might have been lost there.

So we have two sides, both arguing that their opponents have no evidence against them. But do either have positive evidence for their position? Well, it seems like there is actual evidence for the claim that they weren’t buried in the cave: birds.

The author of the review notes that there is scattering of small mammals remains inside the burial chamber. This pattern is seen in the entrance to other caves, where birds of prey take shelter and consume their prey. Hence the scattering of small mammals. As such, the author concludes, this is a clear sign that the cave was a lot more accessible in the past. It’s unlikely birds of prey could have travelled in the dark through all the twisty turny passages to get to the chamber in its current format.

And just in case you think that interpretation is stretching a bit far; it’s worth noting bird bones were actually found in the cave. There was also evidence of land snails; which typically avoid dark passages. Again, more evidence the chamber wasn’t always so difficult to reach.

If it was more open in the past then the chamber may well have  been used by carnivores as shelter whilst they eat their prey. And whilst there isn’t any direct evidence of carnivores, the fact that many of the bones of these fossils are missing (and there are few complete elements) suggests that they might have played a role.

Where Homo naledi was found?

Where Homo naledi was found?

Digging up the truth

I was initially skeptical of the evidence for the burial. After all, they didn’t provide any evidence that it actually happened. Just that it wasn’t the result of these other events. Now I feel justified (and slightly smug) by this latest review.

That said, a large part of both sides’ arguments rests on pointing out the absence of evidence for their opponents. So I’m not sure we can really rule anything out yet. The scattering of evidence (and bird prey) suggests that we will eventually rule out the burial hypothesis; but we haven’t quite got there yet.

Fortunately, there’s a lot more to be information about this cave just waiting to be studied. The tough conditions of working in such a tiny space meant they couldn’t examine everything in there. As such, the initial researchers only scratched the surface. Literally, they didn’t even reach the bedrock of a single chamber of the cave.

Hopefully somewhere in there is the final piece of evidence that shows whether or not Homo naledi really buried their dead. And hopefully it shows that they didn’t, so I can continue being smug.

The evidence so far seems to be leaning that way, so I’m not going to stop feeling smug any time soon.

tl;dr

Did ancient hominins carry out a burial? The lack of evidence for alternatives led many to conclude yes; but that evidence isn’t as clear cut as they think.

References

Dirks, P. H., Berger, L. R., Roberts, E. M., Kramers, J. D., Hawks, J., Randolph-Quinney, P. S., … & Tucker, S. (2015). Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa. eLife, 4, e09561.

Val, A., 2016. Deliberate body disposal by hominins in the Dinaledi Chamber, Cradle of Humankind, South Africa?. Journal of Human Evolution.

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4 thoughts on “Pre-human burial by Homo naledi challenged”

  1. ThQ says:

    Great summary of the current research on the subject, I guess the fundamental issue again here is that we seem to be looking for things that set us clearly apart from non-humans (as in non modern homo sapiens…). Burying the deads could be an answer to that question and its validity is at stake here, which is why we doubt/doubted that say Neanderthals buried their deads and even more so for H. Naledi. This is also why the suggestion by the authors of the discovery that this was a burial became an even bigger news/buzz than the discovery of the fossils themselves. When will we just stop looking for things setting us apart from non H. sapiens? It hope it will be soon as it will certainly calm down many heated debates.

    1. Adam Benton says:

      I suspect the focus on the burial is also partly caused by a lack of information about the rest of the find. It was uncovered around 2 years ago; yet only 3 papers have been published on it (with an extra two about the burial idea). This drought of information has forced speculation.

  2. Dr George Beccaloni says:

    Hi, thanks for all your very interesting blog posts! I have been puzzling for a while over why H. naledi might have deliberately disposed of their dead in a cave and have just come up with an idea which seems plausible to me at least! ‘My’ idea (someone has probably suggested it already – like most of my other ‘new’ ideas) is that they did this in order to ensure that dead corpses were disposed of in a relatively inaccessible place so that they didn’t attract predators and dangerous scavengers (e.g. hyenas) into the area which might attack living individuals and/or (perhaps less likely) so that individuals who might have died from disease were put somewhere where they couldn’t infect the living (ants do this – http://news.nationalgeographic.com/news/2014/07/140708-corpse-removal-ants-social-animal-survival-science/). Perhaps burial of dead by Neanderthals (if they did) and modern humans also originally developed for this utilitarian purpose and was only later ritualized??

    1. Adam Benton says:

      You’re right that it isn’t necessarily a new idea, but I think you do hint on some interesting new points. Notably the fact that ants carry out this behaviour, but many primates don’t. I suspect it might stem from the fact that ants have a permanent home whilst many other species don’t This raises the possibility that the reason these hominins may have been burying their dead is that they were shifting to more long term occupation than typically seen amongst primates.

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