EXCLUSIVE: What did Homo naledi's brain look like?

Chris Smith spoke to human origins expert Lee Berger from Witwatersrand University, Johannesburg, about his recent Homo naledi discoveries at the Rising Star Cave. He even brought skulls, hands and feet with him...

Lee - One’s an old friend of course. One is the actual type specimen of Homo naledi from the Dinaledi chamber. This is the one that we announced almost three years ago, I guess. We didn’t know how old they were at the time but it was the most complete skull that we had.

Interestingly, if you’re looking at this skull to describe it, it’s a brown skull but the white part in the front is the nose area which we didn’t have. These are some of the most fragile bones in the body and they did not preserve in those early specimens that we were pulling out so we kind of guessed at it. The rest of it all fit together but we had to guess at what the central face would look like so we put a nose on there based on the way the face was angling down and also the advanced features we were seeing in some of the back parts of the skull.

I’m really pleased to say that we discovered a skull in another chamber, the Lesedi chamber, and we announced it about four months ago...

Chris - This is the same cave system, it’s another chamber off of where you discovered these specimens?

Lee - About 110 metres away. Again 40 metres deep; very inaccessible. We found a skeleton there that had a complete skull. This is the skull, I’m now holding that one now in front of us. I’m pleased to say, after all that work, we got the face wrong in the original reconstruction. It’s very clear when you see the second skull (Neo’s) nose, that it’s much flatter. When I hold them up together you can see the difference in the reconstructions.

Chris - You hedged your bets a bit when you guessed, because you gave him a much more prominent nose. More towards what we would regard as human-ish?

Lee - A "Homo erectus-y" kind of thing! And that was being led by some of the shape of the skull. It’s clear though that Homo naledi (Neo’s) skull, and face is much flatter. Much more primitive.

Chris - Just to describe this for people at home: the actual skull vault is a bit bigger than fist sized I’d say...

Lee - Yeah.

Chris - So this would have been quite a small-headed individual. When would these have been running around on Earth? When do these date from these specimens?

Lee - When I was on your show last, we said they must be millions of years old. Every scientist was trying to guess at how old Homo naledi was based on the anatomy of the heads, of the body. There were several papers published saying it was a million and a half, two million, maybe two and a half million years old.

We now know that this population of Homo naledi in the Dinaledi chamber is actually around two hundred and fifty thousand years old. Between about 180 thousand and about 340 thousand with the central point around two hundred and fifty thousand years. That is really young. It’s really kind of put a landmine in the middle of archaeology and palaeoanthropology because that sort of primitive ancient human relative should not have been alive at that point according to what we’d been finding.

Chris - Meghan was talking about the ancient Egyptians burying their dead. That’s the striking thing about these individuals isn't it? You found this in a cave system where really the only way that that they could have got those bodies into that cave system is that they took them there?

Lee - Our very controversial hypothesis that we put forward about three years ago was that the Dinaledi chamber was a deliberate body disposal site. They came down this amazingly narrow shoot entrance. It has enclosures 17½ centimetres wide, say 7½ inches wide, down 12 metres, which is 50 feet or so.

Chris - Because the job advert you put out for people to work on this project said, “I want small, skinny women!”

Lee - No, I didn’t say women. I said I wanted a skinny scientist!

Chris - It’s the only job advert you can actually say these days - legitimately - and say "I want skinny people," isn’t it?

Lee - That’s right! We did hypothesise that they were deliberately disposing of the dead. That’s not been disproved - it still sits as the most valid hypothesis. We now have, of course, not just one more chamber - the Lesedi chamber - we found another chamber. I just came out from underground about 4 weeks ago. Now if one thing when we talk about Egypt or other places and deliberate body disposal like that but not with this brain. It’s just very hard to fathom that they had that complexity, yet we’re faced with “it is what it is.”

Chris - They’re very small-brained aren’t they? If one looks at the inside of the skull you can some idea as to what bits of the brain might have been doing what and what the behaviour of an animal may have been because it tells you about the size of the underlying brain. So if you look at these specimens, what does the brain look like?

Lee - Well, in fact that paper’s just about to come out...

Chris - Oh damn!

Lee - No, it’s okay. I’ll go ahead and break it!

Chris - Exclusive for the Naked Scientists then!

Lee - I’ll give you the exclusive! it’s very complex. Our scientist who’s been studying our image of the brain that’s pounded out on the inside of the skull all his life said "it’s finally the brain I’ve been looking for my entire life, because it’s very advanced. It’s very complex but it’s tiny."

Chris - Did they have language? If you look, is there a swelling on the left hand side roughly where the language centre might be? Were they talking to each other?

Lee - There is. Broca’s area is enlarged; there’s bilaterally symmetry. We don’t know if they had language. I can tell you that if we are right about this sort of very complex behaviour, I would be very surprised if they did not have a language or a communication much more complex than any animal communication we know of.

Chris - So maybe not hieroglyphs, Meghan, but they could have been saying something!