Lessons from our ancient ancestors

0:11Andrea Manica:Hello,

0:17Andrea Manica:welcome to the Naked Scientist podcast, the show that brings you the biggest breakthroughs and talks to the major movers and shakers in the worlds of science, technology and medicine. I'm Chris Smith and today how our ancient ancestors going back up to hundreds of thousands of years made the leaps that they did from ritualistically burying their dead to art, avoiding disease and even discovering drugs and medicines.

0:49Andrea Manica:Anatomically modern humans like us have been around for about 300 ,000 years. That's roughly when we split from an ancestor we shared with Neanderthals. In the time since, we've mastered materials, medicine, machinery and even moon travel. But one thing really stands out about our species. We revere our dead. And we have evidence going back at least 100 ,000 years that we afford the departed special treatment. Historically, people argued that our big brains and social instincts, factors that make us so successful as a species, are behind this inclination. But then, along came a remarkable discovery from South Africa a decade ago.

1:29Andrea Manica:A deep cave system crammed with the quarter of a million year old remains of a new and completely different species of human ancestor, Homo naledi. These creatures were not like us. They were from a different evolutionary path and only distantly related to us. They also had much smaller brains than we do. but a cave full exclusively of their bones suggested they were burying their dead. Initially, other paleoanthropologists were very sceptical, but now new research has added a significant and even more compelling twist to the story. By analysing a gene product called amylogenin, which is found in different forms on the X and Y chromosomes, Lee Berger and his colleagues have found that the remains in the cave are all female.

2:18Lee Berger:It's all about Homo naledi and questions that have been building around this fascinating species. Homo naledi is a kind of quick backstory we discovered in 2013. We announced in 2015 as a new species in the genus Homo, a very primitive species in look with a very small brain, about the size of a chimpanzee, but on a very tall, slender, bipedal body that looked like it should have been 2 million years old, but existed in southern Africa at 250 ,000 years old. Perhaps even more remarkable was the situation we found it in. Chambers deep inside the Rising Star Cave system just outside of Johannesburg, hundreds of meters back, dozens of meters below the surface, in a situation where initially they were alone.

3:10Lee Berger:There was nothing there but them. Just explain the significance of that. every other ancient human, ancient hominins, ancient human relatives, and even Neanderthals are almost always found with lots of other dead things. And the reason they're found with lots of other dead things is either the places they die or are found to die are accessible by other things, whether they be carnivores, scavengers, things that get lost in caves. Homo Naledi was alone in this situation, there were almost no animal remains with them. And when I say almost no, there were a couple of baboon teeth eventually, some microfauna, mice, rodents, that kind of things, rabbits, small animals, and no other animals their same size.

4:01Andrea Manica:And how many Naledi specimens were there?

4:04Lee Berger:In the first instance, 15. That has grown to almost three dozen right now, But I'll give you a little secret. There are dozens and dozens more bodies in there. We know they're there. We can see parts of them. We know where they are.

4:20Andrea Manica:So you have a huge assemblage of exclusively one species in a hard-to-access cave system deep underground near Johannesburg. How do you explain or how do people explain that?

4:32Lee Berger:Well, when we first announced them, we didn't have an explanation other than what we would apply to humans. Humans are the only other animal that you would find that situation in. And the reason you would find humans in that actually fairly commonly is we separate ourselves at death. So we hypothesized at the time that they were deliberately disposing of their dead. Now, that went over like the proverbial lead balloon. The idea that a small-brained hominid would be practicing some sort of ritual or repeated behavior to separate its dead is very complex.

5:08Andrea Manica:And just to be clear, if we look at not just the remains, which you can date, but the context they're in, you can date that and it isn't that someone put the remains there later.

5:20Lee Berger:No, that's right. They appear to be the only thing interacting with the system. There's no evidence that carnivores took them there. There's no evidence of catastrophe. They came in slowly over time. And even more remarkably at the time, we did note a very interesting thing about them. They all looked alike. They didn't vary. Now, we had infants. We had neonates. We have young children. We have young adults. And then we have adults. And we have elderly. They looked like a symmetry population. There were some that were a little larger than each other. And we did what I guess any ball just naively would do.

5:58Lee Berger:We said the larger ones are males and the smaller ones are females. And if you go back and read those original papers in eLife, and you should, you'll see we were right on something then. We knew there was a problem. We said they were the least sexually dimorphic species ever discovered. The only comparables would be some human populations of closely related individuals. And that was our explanation. Right in front of us was the answer to one of the most extraordinary discoveries I will ever be involved in in my entire career.

6:37Andrea Manica:Are you saying then that you were wrong, that they're not males and females?

6:41Lee Berger:I'm saying that we were absolutely wrong because a few years ago, I took samples to Copenhagen, a lab there, where they had advanced a technique looking at ancient proteins. Part of the output of those ancient proteins was looking at the amylogenine or gene in Y, the absence or presence of a Y chromosome within that. We could tell that from these ancient proteins. And almost immediately, we began getting very odd results. They had no Y chromosome. So we took some more. They also showed no marker for a Y chromosome. That would run up to 23 samples being done.

7:23Andrea Manica:And let's be clear, the absence of a Y chromosome, if that were, say, you and me, it wouldn't be you and me because men have Y chromosomes. Women have exclusively X chromosomes. So you're kind of speculating that the absence of Y says, well, these are all one sex and they're all not male.

7:40Lee Berger:I think it's a little more than speculation in the sense that, yes, there are individual situations where a male may not show these markers for a Y chromosome, but they are literally fractionally small. These are females.

7:58Andrea Manica:So if they were ritualistically interring their dead, they were doing it with a bias towards females. They were only interring in that cave females.

8:08Lee Berger:That is what they say. You may remember that a few years ago when we talked about this on your show that we argued that they were burying their dead. We said we moved beyond ritual body disposal to burial. We also argued there were engravings on the walls. now we have evidence that there is sex selection in the dead only little girls went there and i'm going to say something here that 50 are sub-adults many of those are infants and babies there are no baby boys if this were some matriarchal society or some collection of women and children. They'd be baby boys. They, Homo naledi, a non-human species with a brain slightly larger than a chimpanzee, was selecting its women and girls for this space in depth.

9:08Andrea Manica:Tell me more about the other elements in the context that you're referring to, engravings on the wall and so on. There are these geometric engravings on the wall.

9:17Lee Berger:They've been carved there into the wall. They look like they've been done repeatedly over time. Some of them have been covered up with earth from the floor of the cave and maybe some other substances. They're triangles, they're hashtags, they're pounding marks, there are sort of chevron kind of markers on the wall, there are squares, ladder-like structures. They're all right above these graves. We have no evidence that humans were ever in there.

9:46Andrea Manica:It's also damn nigh impossible to get in there. I mean, I remember when you published the advert for staff, and it was the most politically incorrect advert you probably ever see. I only want female, very skinny archaeologists to come and excavate something. I think it was worded slightly more diplomatically, but it's hard to get there. It's dark. How on earth would they have seen what they were doing? Because they had fire.

10:10Lee Berger:Do you know that? How do you know that? We've got evidence of fire all through there. I announced that a few years ago. you're going to see some work on the dates of those and that. But there's evidence of fire throughout the system. Now, what's interesting is that we have now found burnt bone remains of animals and stuff, but not in those chambers. They took fire into those chambers where they buried their dead.

10:35Andrea Manica:And what sort of time spans the earliest to the oldest, sorry, the earliest to the most recent specimen? It wasn't just, say, one particular individual with a penchant for caching things like a squirrel, and it just happened to cache dead bodies of females. Was there evidence of a culture here? It's going on over a period of time that would have outlived one individual.

10:55Lee Berger:Oh, absolutely. And we have strong evidence of them digging through dead bodies, upturn the bones, and then put them back. But if you go back and read some of the papers we published last year in 2025 on the burials, you can see that they also did some interesting things like they put the heads back very carefully in the same direction. We can see that this is kind of gross, but the rotting tidal lines on the skulls of where the bodies next to them would rot, send their fluids out and leave a tidal line. The head would be disrupted by a later digging event and then the tidal line would appear.

11:31Lee Berger:So this is a generational thing. we are looking at a complex non-human culture.

11:39Andrea Manica:Sends a shiver down your spine, doesn't it? So it looks like the instincts towards rituals in death might date back far farther than we believed and wasn't just the sole preserve of us anatomically modern humans either. Lee Berger there, he's just published that work in the journal Cell this week. Now from rituals in death to another form of ancient culture and that's art. At the Gower near Swansea, just over a century ago, ten horizontal red stripes were discerned on the wall of Bacon Hole Cave. Archaeologists didn't initially know what they were, but they've now been identified as Britain's oldest prehistoric art, dating back more than 17 ,000 years.

12:23Andrea Manica:It's thought that these paintings may have been created by early ancestors as they surveyed the changing seasons and dinner over what is now the Bristol Channel between Wales and south-west England. This was just as the Ice Age was ending, so the land that these people, who were some of our direct ancestors, were exploring was very different to the estuarine environment that it is today. George Nash at the University of Coimbra in Portugal has the story.

12:53Rod Flower:it's quite some way into a site called bacon hall it's in a side chamber which you'd expect and on the wall are a series of 10 bars painted in red hematite and they are covered by a calcite flow or a speleotherm which covers over the art it's very very difficult to see and this is probably one of the reasons why it was dismissed way back in 1928 so this is not a new discovery this was discovered and then lost effectively oh goodness me yes yeah yeah this was discovered in 1912 by a geologist called professor william solace uh from oxford and what we call the father of prehistory the abbey broyel who was a french monk who became interested in archaeology prehistory and they met up in 1912 and decided to walk around the caves of the gower at the time william solace was actually excavating Pavlin Cave.

13:50Rod Flower:And so they went into Bacon Hole and found this remarkable discovery. The news was sent to the Manchester Guardian and the New York Times. It went round the world. And then luckily, it was picked up by a guy called William Morgan in 1913, who did a really very, very good detailed scientific report on this, published in an obscure journal, unfortunately. But he did took the first photograph and the first photograph is obviously black and white. Unfortunately, it was published sideways on. So it looks like the lines, which are actually horizontal, are portrayed as being vertical. So that needed to be rectified for a start when we were doing our research.

14:34Andrea Manica:But how did it get overlooked, forgotten about, and then it's back in the frame again with you looking at it?

14:41Rod Flower:Spectres of ancient monuments were going down there and obviously from time to time verifying it, if they could see it or not, and they couldn't. And I think what it basically is, without being too arrogant, is that they didn't know what they were looking for. If you're looking for an Iron Age hillfort, you'll find it because it's pretty obvious that it's a hillfort. But if you're looking for painted rock art, which is hidden behind a white calcite flow, it's very, very difficult to see. And you do need a good pair of eyes and experience working in caves and working with rock art to actually identify it.

15:15Rod Flower:And how did you get involved? right well i'm i was teaching at bristol university uh for about 19 years and one of my uh jobs was to take students uh on an annual visit to uh to palolithic sites to get some give them some idea about what it felt like to be in the palolithic so i wasn't particularly looking at rock hard and we tried pavlin cave it was too dangerous to get to uh we tried other caves and then bacon hole came up for about two or three years so for two or three years i was taking him down here, telling him the same stories I'm telling you now about his history of archaeology. And I never found it.

15:53Rod Flower:So in 2022, I was doing a filming project with the Discovery Channel. And I was with a colleague, Barbara, and she said, hey, what's this then, George? And then pointed to these horizontal lines or some of the horizontal lines behind this calcite flow. No, we were actually talking about it as she discovered it. So it was a remarkable sort of coincidence and a complete elation about how we just discovered or rediscovered the rock art. And if you go down there now, you will see just about the faint red bars, 10 of them in a row, horizontally laid, painted out. And that's how we discovered it. But there's still work to be done there because it's not just the bars we found.

16:35Rod Flower:We found other things as well. But because I was specifically interested in focusing on the bars, I didn't really have much chance to sort of expand the research or survey of that particular side chamber. So who painted it and when? We actually got to three layers, three stratigraphic layers. One was 17 ,100. The other was around about 4 ,000 before present. And the other one was 2 ,000 before present. So we've got really a prehistoric development of a calcite flow forming over the painted imagery.

17:10Andrea Manica:You've looked at one line, there are 10. So is it possible that someone was coming back every 100 years, every 1000 years? And in fact, if you looked at other lines, you get different dates.

17:21Rod Flower:I think it was all done as one event. We did analysis on the hematite, which is the red ochre, the colour, the pigment that constructs the 10 bars on the panel. And that came locally, probably actually within the side chamber itself. And we know that was put on with finger dots so they were mixing the pigment with water and then they were applying a wet gloopy paint onto the panel using their fingers how they did it i do not know very very straight line it could be as you say as a series of 10 events maybe done annually but because of the the fragile nature of the paints we didn't allow ourselves to do 10 lots of samples from the 10 different bars only because when you start to scrape away the calcite you can potentially damage the the actual paint itself so we were we restricted ourselves to um 10 samples from different parts of the panel not just the bars itself but there are other things there which we had to sample and then we had one date um which gave us 17 100 now what we've got to do uh i'm I'm now in negotiations with the landowners of the National Trust to do more sampling there at some point in the near future.

18:39Andrea Manica:Now, 17 ,000 odd years puts us at the tail end of the ice age that had gripped the planet. Most of the UK was under still quite considerable amounts of ice. It was very cold at that time. Sea levels would have been a lot lower. So presumably there wouldn't have been a Bristol Channel like we have now separating Wales from the north of the southwest. as it were. So who were these people who were doing this and what were they doing there?

19:05Rod Flower:They were all early modern humans. They're people like you and I in a very, very cold climate. So average summer temperatures would be around about minus 10. If you were to walk out of the cave and then look northwards, you would probably see a line of ice, maybe a kilometre high. The Bristol Channel would have been a large, fertile plateau, but permafrost. And what you would have is mosses sedges, lichens and grasses which will be growing there in the spring and summer months and that will be an ideal environment for megafauna, large animals such as mammoth, bison, elk, reindeer and horse. So those migratory herds will be coming from the south to take advantage of the rich feeding grounds of what is now the Bristol Channel and you would have had hunter, fish and gatherer communities small communities watching out in the spring or maybe even following the herds and staying in those caves during those warmish months of the hunting year so that's the reason why we have a large match of bone coming from different caves along the coast and so quite clearly they were killing those animals dragging them up into the caves and then procuring their their meat and also the carcasses for things like skin clothing and also for bone tools etc etc

20:29Andrea Manica:but why they made those lines on the cave wall and what they were depicting is still a mystery a fascinating story george nash there the naked scientists podcast is produced in