Ritual: the story of Homo naledi

Some of our higher mental functions might not be quite as unique as we thought, but what about other aspects of culture, like religion, or rituals? Again, we had complacently assumed that these were the sole preserve of us modern humans. Or maybe not. Because the announcement in 2015 of the discovery of another early human ancestor, Homo naledi, suggests these individuals might have been burying their dead. Lee Berger told Chris Smith how this discovery came about...

Lee - Well, first to correct it - I didn't do the discovery - my team did. It was discovered in a most remarkable series of events lead by two amateur explorers who were working with us, who shimmied down a seven and a half inch slot, almost sixty feet underground into a chamber and there, in that chamber, was the most remarkable hominid cache perhaps ever discovered in history.

We did an underground expedition in November of 2013 to recover what I thought, wrongly, was a single skeleton. At the end of that 21 day expedition, we'd found more individual hominin remains than had been discovered in South Africa in the last 90 years. It was tremendous and there are thousands of remains left down there.

What was important was that not only was it a new species, this tiny small-brained species with amongst the smallest brain ever found in the hominid era - 450-550 cubic centimetres, just slightly larger than apes.

Chris - So that's a third of say your brain size, my brain size?

Lee - That's right. And individuals that are about five and half feet tall, which is quite tall, but with very ape-like shoulders but human-like hands that are very, very curved like the most primitive ancestors. A primitive pelvis like Lucy's, but long human-like legs and human-like feet.

That would be incredible in itself to find a cache of new hominid species unexpected like that but what was, I think, even more remarkable was that we eliminated pretty much every other reason for them being there. They weren't dragged there by predators, they weren't washed there, they weren't - as I received an email yesterday - eaten by a giant snake and deposited there, or many other things. But the 15 individuals that we've taken out so far, and there are many more in there, we believe were placed there or dropped there by members of their own species.

Chris - Now just to be clear, this is in South Africa. It's not far from Johannesburg?

Lee - It's right outside of Johannesburg in an area that is called the "Cradle of Human kind" - a UNESCO World Heritage Site. And many of the richest fossil discoveries in all of history, some of them that Richard was referring too. Even archeological discoveries like some of the oldest evidence for the controlled use of fire at a site Swartkrans is only 800 metres away from here, it was right under our nose.

Chris - Is there any other explanation for how these individuals could have got there, such as, they fell in or they had another entrance and it was there home and just got locked in and couldn't get out?

Lee - We see no evidence of collapse -  they came in over time. They didn't come in all at once - it wasn't a mass death. There weren't  washed in there - there's no predatory damage. So we came to the, perhaps controversial, conclusion that the best explanation was this tiny-brained, ancient human relative was likely putting it's dead in this place, separating them from other animals and caching them away. Now why is that remarkable? People will say - oh elephants do that, there are elephant grave yards. No they don't.

Chris - Could they not have been driven in there by a more intelligent being that was using them as food?

Lee - I think you're asking a question that often I think my colleagues and I find remarkable. Why would we look for a special pleading case, inventing some hurricane outside, or asteroid coming, or humans ritually disposing in a pet cemetery sort of way, rather than just accepting we've been wrong about human special behaviour, human identity, and the idea that we're the only creature that could possibly understand it's own mortality, or some of the other implications, or want to keep it's dead away from the natural environment because they know, as individuals, they are going to die?

Chris - It wasn't easy for them to get in there was it - I wonder why they went to such extraordinary lengths to do that?

Lee - Well, that's a really interesting question and I think all you would have to do, if we are right about this hypothesis, is look at the great extreme efforts that humans go to to prevent their bodies from being taken by the natural elements. We build tombs, we build tunnels, we build catacombs. If you are not in a constructive age, then perhaps finding somewhere very deep and remote within a cave is the best place you know that nothing's going to get to your body.

Chris - You've been quite cautious about dating these specimens. Do we know how old they are, or are you prepared to admit how old they are yet, or do you not have the evidence yet?

Lee - I know how old they are right now; my colleagues know how old they are right now. We are in the process of peer review submission of the papers and peer review - it won't be long. We've been cautious for good reason, we wanted the morphology judged for itself . People have said they're like primitive Homo erectus. People have guessed at the age; people have said 2 million years old, a million years old.

I can tell you that whatever age Homo naledi is, which you'll learn about early next year, it's going to be quite shocking to the entirety of the archaeological and paleoanthropological community because we have not only discovered the species exists but also this potential complex behaviour.

Chris - And these are individuals who are clearly not our ancestors - they are quite different from us.

Lee - We don't know that. The other lesson that came first from [Australopithecus] sediba in 2010 in Homo naledi is that we should be extraordinarily cautious about trying to put pins and say this is our ancestor, this one gave rise to us. Firstly, the fossil records showing that we don't have that amount of information. There are many different species that are out there. Second, the genetic information, the information from proteins, everything else is telling us that there may even be inter-mixings. I think this linear idea of evolution needs to be replaced by something like a braided stream idea that species diverge and converge back and forth at different times and that we are a result of this very deep, very complex experimentation in evolution of hundreds of thousands and millions of years.

Chris - I think we're going to have to have you back aren't we Lee to fill us in on the rest of it?

Incidentally, Tomos Proffitt is also with us. Tomos - do your primates that you study, to they show any interesting ritualistic behaviour?

Tomos - Well, interestingly a couple of months ago there was a paper published about the chimpanzees in the Thai forest in West Africa, and in the Ivory Coast. Where they found that many many chimpanzees. Basically you have these large trees with large buttress roots, and within these buttress roots they found these very strange caches of stones. And they put camera traps in and they observed these chimpanzees and what they found was that often a male chimpanzee would come rushing past the tree, they would pick up one of these stones and they would throw it back into the buttress root whilst exclaiming or shouting. And they would do this repeatedly and this has been suggested as a potential ritualistic behaviour.

Chris - So it served no benefit to them to just dump a stone - a bit like us climbing up a mountain and building a cairn by heaping up stones, this is what they're doing?

Tomos - This is exactly what they used, they used the word cairn. Yeah. I mean we don't know why they are doing this. It could be something to do with communicating over long distances in the rain forests. I mean they make a very loud noise but they equally make a very loud noise when you hit one of these buttress roots. So they don't know why they're doing this and so the general rule of thumb is if you don't know why you're doing something or why they're doing something it's a ritualistic behaviour.

Chris - Thank you Tomos.