Science Vs - Why Fossil Nerds Are Pissed Right Now

Episode Date: September 28, 2023

The smash hit Netflix documentary “Unknown: Cave of Bones” has kicked off an all-out science brawl. The film makes extraordinary claims about a strange ape-like creature that lived hundreds of thousands of years ago — claims that rewrite what it means to be human. But some scientists are pushing back, saying that at this point, these extraordinary claims aren’t backed up by extraordinary evidence. So, what’s going on? Is “Cave of Bones” a Cave of Lies? We chat to the man at the center of the controversy, National Geographic Explorer In Residence Lee Berger, as well as a couple of the scientists pushing back against his work: Professor Andy Herries and Associate Professor Jamie Hodgkins. Find our transcript here: https://bit.ly/ScienceVSCaveOfBones  In this episode, we cover: (00:00) ‘Cave of Bones’ is a hit! (02:55) Lee Berger, Explorer in Residence (07:10) Meet Homo naledi (14:09) Extraordinary claims (20:54) The media campaign and the backlash (25:16) The evidence for burial (32:00) The evidence for rock art (40:54) Cave of Insufficient Evidence? This episode was produced by Joel Werner, with help from Wendy Zukerman, Michelle Dang, Rose Rimler, and Nick DelRose. We’re edited by Blythe Terrell. Fact checking by Diane Kelly. Mix and sound design by Bumi Hidaka. Music written by Bobby Lord, Emma Munger, Peter Leonard, So Wylie, and Bumi Hidaka. Thanks to all the researchers we spoke to including Dr Bridget Alex, Professor Michael Petraglia, Dr Kimberly Foecke, Dr Sven Ouzman, Dr Elizabeth Grace Veatch, Dr Flint Dibble, Professor Tim White, and Professor Bernard Wood. And a big thank you to Lindsey Cherner, Jill Harris, Jack Weinstein, Katie Vines, the Zukerman Family and Joseph Lavelle Wilson.  Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hey, Wendy here. You're listening to Science Versus, and you better dust off your hard hat. Because lately, a few of us have been obsessing over a brand-new Netflix documentary. It's a doco that is shaking up the science world. It's one of the biggest moments in human history. It's called Unknown Cave of Bones, and it's all about this recently discovered species called

Homo naledi. It walked the earth hundreds of thousands of years ago, and it's a hominin, which means it's on our family tree. It's like a very distant cousin. And in this doco, they made some amazing claims about what this strange ape-like creature got up to. Claims that kind of rewrite what it means to be human. Where do we come from? Where are we going? Why are we the way we are? This doco has been a smash hit.

It was the second most watched film on Netflix in the first week of its release with 6.5 million views. This is for a nerdy documentary. We're not talking about Bridgerton the movie here. I mean, it's amazing. But the thing is, while people were kind of frothing over this doco, not everyone loved what they saw. No, I mean, it's frustrating to watch.

Well, I mean, I don't think I have a colleague that wasn't astounded by it and wasn't frustrated by it. Now, these scientists might not sound pissed, but they are. It's just how scientists talk. And, I mean, things got really nasty when it came to this doco. There were flame wars on social media that led to one senior scientist blocking colleagues and friends. Nerdy YouTube

videos were analyzing the controversy. And for typically subdued academics, this has basically become a scientific shitstorm. It's such a flimsy house of cards built narrative that you pull any one of those cards out and the entire thing falls down. You say what you want to say and you know that when the fact checkers come out, people just won't pay attention. So pay attention because today,

the fact checkers are coming out. We are finding out exactly what is going on here. Was this entire doco a cave of lies? When it comes to this doco about our early ancestors, there's a lot of... Flimsy, house of cards built narrative. But then there's science. Science versus cave ofones is coming up. I'm Rana El-Khelyoubi, an AI scientist, entrepreneur, investor, and now host of the new podcast, Pioneers of AI.

Think of it as your guide for all things AI, with the most human issues at the center. Join me every Wednesday for Pioneers of AI. And don't forget to subscribe wherever you tune in. It's season three of The Joy of Why, and I still have a lot of questions. Subscribe wherever you tune in. So brace yourselves. Get ready to learn. I'm Jana Levin. I'm Steve Strogatz. And this is... Quantum Magazine's podcast, The Joy of Why. New episodes drop every other Thursday, starting February 1st. Welcome back.

Today on the show, we are looking into this documentary from Netflix called Cave of Bones. Watching it, it presented some amazing discoveries, but it has also courted a huge amount of controversy. And supervising producer Joel Werner, you have been swimming in this controversy for months now. What first, like, attracted you to this story? Yeah, look, you know, I haven't seen anything quite like the reaction that this film has got, like, in the scientific community. Is the whole doco, like, a hoax? Where do we begin? Where do we begin?

Where do we begin? That's what we're going to find out. Jesus. I wanted to dig into exactly why everyone was so up in arms about this film. And I guess to start, we have to start with the man who sits at the center of the film, a guy called Lee Berger. So I'm Lee Berger, and I'm an explorer in residence at the National Geographic Society. I have some other titles.

I was hoping you were going to say explorer in residence, because I interview a lot of people in my job, but I've never heard a title that's quite as cool as explorer in residence. It's an oxymoron, isn't it? Yeah, exactly. If they see me, I'm not doing my job. So, Lee Berger is no stranger to controversy. Like, just a few weeks ago, he sent two fossil specimens, two actual fossils from South Africa, into space on a Virgin Galactic spaceflight. What? Why?

Why did he do this? There was no scientific reason for this. It was just a bit of a publicity stunt. Lee got the permits he needed to do this, but the scientific community have been up in arms about the decision. Yeah, yeah. But at the same time, there's this other version of Lee who's like a really important scientist and has been making groundbreaking discoveries for years,

like what his team found in the cave that's at the centre of this documentary. So the cave in Cave of Bones is found in what's called the Rising Star Cave System, and it's just outside of Johannesburg in South Africa. And now the cave is real, right? Yeah. The cave system is real. No one's denying the cave.

Like the cave is 100% real. And also like these fossilized bones that they find in the cave, they're real too. Okay, so no controversy there. Thank you. Okay, excellent. That's, yeah. But the thing you need to know about the cave is it's really difficult

to get into. Like this isn't your kind of family-friendly cave tour with the steps carved into the rock and a cute little hard hat. This is like proper squeezing through super tight spaces kind of caving. Every part of it's difficult. You are compressing your body, turning sideways. It's hugely physically demanding. So at points they're like crawling on their stomach with their arms out in front of them. At other times, they're scrambling up these ridges that have these drops on either side that Lee was telling me, if they fell down, they'd probably die. And then at one point, they have to squeeze their way down this super narrow 12-metre vertical drop. And once you're through that, which is terrible in every way,

you pass through a passageway that's about seven or eight metres long into the beautiful Deniletti Chamber. So this Deniletti Chamber is kind of like the stage on which a lot of the action in the film Cave of Bones takes place. And the chamber itself is located like deep within the Rising Star cave system. It's a part of the cave that was first brought to Lee's attention by a few people who'd been exploring there. And when they first got into the Deneletti Chamber, their minds were blown because they saw littered everywhere. Can you guess? A cave of bones? Bones. There were bones everywhere. And, you know, these bones

turned out to be from this new hominin species, Homo naledi. And so the explorers, they took a bunch of photos and they showed them to Lee. And I asked Lee, like, how soon after seeing those photos did he realize that this was something that we'd never seen before? I would love to say that, you know, it was after we brought all the great team together and scientists from around the world. But to be perfectly honest, probably within the first week of getting material out, you got to remember, to be fair, by the end of the first week, we had the richest hominin site ever discovered in the history of the search for human origins in Africa. In the history of the search for human origins in Africa. Wow. might help as a bit of a zoom out here is that over the last, I want to say, 10, 15 years, however long I've been a science journalist even, I feel like the human and hominid tree has just been expanding. Every couple of years, there's these headlines of like,

new hominid discovered, new one. Look, this one's got a weird jaw. Look, this one's got long legs. Look, this one. And some of them are our direct lineage and some of them like pop off the family tree and then like die down. And so how big, when he says this is the biggest site of like, how important is this? So Homo naledi is like a newly discovered species of hominin and no one, like not even the scientists who are being critical of the film are challenging that. Like no one's challenging that. But what makes this site so important is the sheer volume of bones that they're finding there.

So there are thousands of Homo naledi bones in this space. And like there's a Neanderthal site in Europe that's kind of comparable, but compared to hominin sites in South Africa, they have bone counts in the hundreds, not the thousands. So the scale here is just mind-blowing for scientists. Right. If you're going to make a doco about those caves, you'd call it like caves of a couple of bones.

But this one got to be called like cave of bones. You might call it like cave of throw me a bone. Okay. So how many homo naledi are in there, do they think? Well, I asked Lee that question. We are conservatively probably at about 35, 36 individuals that we have out. We've left lots in there

and we have hardly touched this space. So it's one thing to see these fossilized bones, right? But I wanted to get a sense of like what it would be like if we kind of ran into Naledi in the street, right? So I asked Lee to describe it. From 50 meters away, you probably would think, oh, there's just some weird person who's drunk coming in because they would be walking different. But when they walk through that door into the space, you would be terrified probably. It walked on two legs. So get that picture in your mind.

You have a two-legged image of the silhouette. But that's about where the real similarities stop, except for some minor details. Imagine a five-foot-two individual with a head the third the size of what it should be. Wow. Yeah. You know, I mean, say pinhead, you could do anything like that. Okay, so I'm not sure if pinhead is like a technical term here, but like it was because of this small head that Lee thought Homer Naledi lived a really, really long time ago.

I would have said that thing was millions of years old based on the anatomy I was looking at. But it turns out Homo naledi was around a lot more recently than that. So only a couple of hundred thousand years ago. Now, one of the people who actually did like the dating work on the Homo naledi fossils is a guy called Andy Harries. Andy's a field archaeologist and like Lee, he works in South Africa. In fact, Andy's site is just down the road from Rising Star.

So he knows this part of the world really well. And he actually knows Lee Berger pretty well. Yes, Lee and I have known each other for quite a long, long period of time. Andy's a professor of paleoanthropology at La Trobe University in Australia. And this finding that Homo naledi was younger than we expected it to be, it puts it at a really interesting point in time. Because 300,000-ish years ago, another ape-like creature pops up. Us. People were sort of like, whoa, okay, this is, that's unexpected. Because obviously at that time period, it means it's potentially on the African landscape as the same time as our ancestors. So suddenly you've got a situation whereby you've got this species that looks more like older

species in many, many ways. And it's there running around with modern humans. You know, that was a big thing, and I don't necessarily know that we still understand why and how that works. Oh, that's so cool. So this is all amazing and weird and exciting. It's totally cool, right? And so Lee and his team are sitting there, and they've got, like, these 30-something Naledi bodies

deep inside this cave. And they start wondering, like, what are they all doing there? Like, how did they even get into this part of the cave? It's weird because it's so hard to get into. Right. And so one night over beers, they start talking about what possibly could have happened. I remember sitting, we were sitting at a nearby pub one night, you know, after the work was done, and these were really exciting and emotional days. And that's when I and a couple of others raised the question that I think was sitting in everyone's mind. was this might be some sort of mortuary situation that this might have been where bodies had been disposed of by other Naledi. So what Lee's saying here is that Homo Naledi was dragging the bodies of its dead deep inside

this cave system and disposing of them there. And the way he got to this idea was because he just kept finding so many Homo naledi fossils and so few remains of anything else in this space. Like there was a couple of fossilized wing bones. There's a baboon tooth in there, like randomly. But then they saw something in the cave that made them dream even bigger. And this is where things start to get really interesting. In 2018, we discovered holes dug into the floor that had bodies in them covered by dirt that had come from that hole.

So Lee and his team shifted from thinking that Homo naledi was dragging the bodies of their dead and just dumping them back in this deep part of the cave to thinking that they were deliberately digging holes to put the dead bodies into. That's something on a completely different level. They're burying their dead. At that point, even thinking that about a hominin with a tiny brain like this, it was just unheard of. Why is that? Like, why was it unheard of to say something like that? Okay, so there's a few reasons. Firstly, to the best of our knowledge, the oldest known human burial, so we're talking Homo sapiens here, it's from Kenya, and it's estimated to be from about

78,000 years ago. Now, what Lee and his team are proposing is that Homo naledi was burying its dead around 240,000 years ago. So that's like 160,000 years older than what we currently think is like the oldest evidence for a human burial. But also, it's not Homo sapiens doing this, it's Homo naledi. And remember what Lee said, it's got a brain the size of a large orange, right?

A brain that's one third the size of ours. And oranges don't bury their dens. Is that what you're trying to say? It's a big head because we have a big brain. We do special things. And that's the thing. Up until now, no one's ever suggested that something with a brain the size of an orange would bury its dead. This is this idea of human exceptionalism, right? That our big brains make us special and we do special things with those big brains, like burying our dead. And so recently we did the unthinkable

and said we have found graves. Now that may not sound, you know, striking to your listeners, but until the moment we said that a few months ago, that was sacrosanct to human behavior. That was about one of the few last things we had left that we could separate ourselves from other animal cultures. You know, we'd lost tools. We'd lost mourning. We'd lost all this other stuff.

But boy, we had deliberate mortuary practices and particularly burial as our gig. And we're saying we think we've got that too. That's a big deal. The idea that something with a much smaller brain than us could be also engaging in these complex cultural practices, it kind of rewrites everything. It kind of just like wipes the slate clean. It rewrites what we think a brain can do and the sizes of brains that are allowed to do that. It rewrites what's special about humans. And also like the nature of cultural practice.

Like maybe it's not something that's connected to brain size. Like we'd have to rethink the origins of culture if we accept that Naledi is burying its dead. But the thing is, it's not just about the graves. There are other cultural practices that Lee claims to have identified Naledi doing at Rising Star. That's right. That's right, that's right. In the doco, they said that Homo naledi was making art on the caves.

Yeah, so this is when Lee's made his way into this deepest part of Rising Star and he starts walking down the passageway that leads to the denaledi chamber. And as he's walking along, he notices something unusual on the walls. I looked to the left and there were these etchings. There were these marks. You know, the first thing I see is this cross. And then I saw a box and then a triangle, a perfect equilateral triangle. These aren't natural shapes. And in the doco, there's a lot of talk about how this is also quite shocking. Yeah.

Seeing rock art here. Exactly, exactly. It's just like the burial's claim. So, like, Lee is arguing that these engravings were made way earlier than what we currently think is the earliest rock art, like 200,000 years earlier. Okay. And, you know, again, there's debate about whether other large brain hominins,

so like Neanderthals have a similar brain size to us, and we still debate whether Neanderthals made rock art. And so Lee and his team are arguing that, again, something with this tiny brain is doing this thing that we've, up until now, only thought that large brain creatures, large brain hominins do. Bang, Naledi drops in on this. You know, I think that Naledi has shocked all of us. So fast forward to 2023 and Lee and his team start revealing some of these ideas to the world.

So back in June, they announced their findings in a series of what we call preprints. So preprints are research papers where there's been no peer review, like no independent stress test of the science by experts from outside of Berger's team. Yes. I would say this is a naughty thing to do when you're... It's a little bit unconventional for like paleoarchaeology and paleoanthropology.

Unconventional is a polite way to put it. Like if you're a scientist and there's no deep urgency to get your research out there, get it peer-reviewed. Exactly. And there'd been a little bit of talk on the grapevine that these papers were coming and that they were going to be published as preprints. Like Andy Harry's heard about this before they came out. I mean, Lee doesn't keep secrets very well.

I mean, he just quite openly tells people about stuff. So yeah, I mean, people are always aware that things are coming. There's three papers. I mean, one deals with the idea that Homer and Elodie buried its dead. The other one deals with the idea that Homer and Elodie created rock art. And the third one is more of a just sort of chat about the issue of, you know, whether we should infer symbolic behaviours and those sorts of things that we normally attribute to modern humans,

maybe Neanderthals, to something that has, you know, a small brain. So on the very same day that the preprints were released, there's this big press event that launches a whole media campaign based around this new set of findings. We'll be publishing a book about these findings titled Cave of Bones. And these findings will also be shown in Netflix's Unknown Cave of Bones, which premieres on July 17th as one of the films in a four-part documentary. So a whole media campaign launches all based on these fresh ideas that Naledi buried its dead, that Naledi made rock art, ideas that hadn't been stress tested by other experts.

And so the scientific community gets really pissed off about this. Well, I mean, I don't think I have a colleague that wasn't astounded by it and wasn't frustrated by it. I really wanted to hear what Andy sounded like pissed. It's very similar to what he sounds like not pissed, but I feel like that checks out. So Lee and his team had initially tried to release these findings in the more traditional, like, peer-reviewed way,

but when I interviewed him, he told me that they couldn't get the papers published, quote, in a timely manner, end quote. Homeowner ladies waited 200,000 years. But a couple of months, maybe even a year, could not. Exactly right. Like a bunch of people I spoke to when I was reporting this story, they were kind of suspicious that Lee was rushing the science, rushing the publication of the science to keep up with this media campaign. Here's Andy Harries.

I think, obviously, the impending timeline of the Netflix documentary and the book and everything probably had something to do with that. So Lee denies these claims, but while all of this is going on, we finally get to hear what independent experts, what the scientists think about the preprints. And guess what? They're not happy. So the journal that published the preprints had invited scientists to peer review the work. Jamie Hodgkins was one of the scientists who took a close look at the evidence for Naledi burying their dead. And she's also an associate professor

of anthropology at the University of Colorado,i burying their dead. And she's also an associate professor of anthropology at the University of Colorado, Denver. So I was getting frustrated because the press release was going all over. And meanwhile, this narrative is out there without anything checking it. So like one question that we often ask for stories like this,

if you had to give the Berger science a grade, how would you grade this science? An F. Well, no, no. I mean, the site itself is amazing. So if the question is like how... The science in this paper, like if you had to give this paper a grade.

Yeah, I would fail it. And she did, it sounds like. Yeah, Jamie's like clearly not pulling punches when she talks about this work. I mean, seriously, it's just, it's really amateur in how it's written. It's amateur in how it's organized and presented. And the citations are really concerning. Like, I just don't understand how it's so poorly cited. Like, on behalf of our show, I am deeply offended by the poor citations.

I'm feeling that as well. But I feel like I'm more offended or concerned by some of the other stuff that Jamie was saying. I mean, that this paper is amateur, that she's failing it. I mean, what's so bad about the science here? How are they failing? Well, that's a question we're going to excavate after the break. Welcome back. Today on the show, we are talking about the huge controversy

surrounding the Netflix documentary Cave of Bones. Supervising producer Joel Werner is walking us through what went wrong here. Yeah, look, I'm lacing up my running shoes. I'm getting the sweatbands out. We're not walking anymore. We're going to break into just a light jog and get into the evidence. I'm ready. Oh, wow. Okay. I'm ready.

I'm pumped. I'm ready. I'm ready because when we left off, Jamie Hodgkins had failed Lee Berger's work and I want to know why. All right. So, first, we're going to dig into the idea that Homo naledi buried their dead. Great. Now, it might sound super obvious, but like when you're trying to say whether or not something from the deep past is a burial, you've got to prove that it's a burial, right? You can't just assume that something is a burial. You've got to prove it. The line that'll be on my tombstone, by the way.

I thought you'd have factulator. All right. So a big part of proving something is a burial is being able to identify what's called the burial pit. Because like, how can you tell the difference between a hole that's been dug in the ground to put a body in and a body that's just been lying there and has been naturally covered over over time. Well, there are some... Right, because we're talking 200,000 years ago, so it's all just like bones with dirt. Exactly. There's like layers and layers of sediment, right? But there are scientific techniques you can use to figure out the difference between those things. Here's Andy Harry's.

My expectation would be that if you've got a grave cut, even if you've got material that was dug out and the same material put back in, you should be able to see it if you do something like micromorphology. So one of the methods that nearly everyone uses now is micromorphology of the sediments. Micromorphology. Micromorphology. It's not just any kind of morphology. It's little. It's not macromorphology. Definitely not. What is micromorphology? Micromorphology is a super cool process, right? And it kind of happens

adjacent to excavation. So the whole idea is that as you're excavating a site, you're taking samples of the sediment, right? So the way the soil, the way the dirt has all been layered up, you're sampling that so that you can examine it under a microscope. And what are you looking for once you see all that sand? So what you want to do is take these sedimentary samples from all over the site, right? So from everywhere. And if you do it correctly, you should be able to figure out whether the sediment that's in and around the remains of the body is different from the sediment elsewhere in the cave, right?

Because if you think about what you need to do to make a burial pit, you dig soil out, you put a body in, and then you push soil back on top, right? So the soil that's in around the body is going to be this like jumbled up, whereas the soil that's around, the sediment that's around that pit should all have its original layers intact. So if you do this micromorphology, you should be able to say this dirt is different to this dirt. So it's like if you had a layer sponge cake

and you stick your hands in the middle and scoop it out and shove the sponge cake somewhere and then you like bury some cherries or whatever in it and you shove it back, you would be able to see that middle bit of the sponge cake all messed up. Totally. It's a lesson you only have to learn once in life, that you can't just go and dig cake out with your hand, realise the error of your ways and then just very quietly replace the cake.

People are going to know. There's going to be evidence. That's right. That's right. And with the help of micromorphology, you're going to be f***ed. Would-be cake thieves, be warned. So, no micromorphology? Berger didn't do any so remember earlier i said that the oldest known homo sapiens burial was from like 78 000 years ago right the research outlining that

discovery was published in the very prestigious journal nature and it's kind of a famous paper in this space it's become one of my like favorite go-to papers when I've been working on this story. And so when I asked Lee about whether he'd used micromorphology to analyze the Homo naledi remains, he said that he actually modeled his own research on that nature paper. We in fact mirrored that paper. We demonstrated with real images that the floor and the sedimentary structure of the

lorm, the sort of orangey layer that's there, has been disrupted and that it is disrupted and in fragments in the dirt that surrounds a body. We do that micromorphology. But look, despite what Lee said there, when Jamie looked at the paper, she didn't see the evidence for a burial pit. There's nothing convincing there. You know, maybe it's possible, but there's nothing that has been presented that's convincing that there's a burial pit. Now, Jamie wasn't the only peer reviewer to feel like this. Like another one said, quote, I did not see the argument in support of a burial pit, end quote. And quote, more excavation and the use of geoarchaeological techniques,

especially micromorphology, are required to sort this out, end quote. So I went and spoke to another expert, an independent expert who hadn't been involved in any of the peer review, but has substantial experience with these kind of micromorphological techniques. And their opinion was that like, while Lee Berger did attempt to mirror the methodology of that Nature paper, quote, he executed these methodologies incorrectly and failed to follow established micromorphological protocol, end quote. So basically they're saying, like, you did some micromorphology

but you did a crappy job. Is that fair? Yeah, yeah, pretty much. And again, Lee told us that he doesn't agree with that. Do you think that they're being harsher to Lee Berger because he's claiming Homo naledi was doing the burial versus Homo sapiens? Yeah, I mean, I don't know that I can answer that question. And the experts I spoke to, I put this to experts

and they were basically like in the paper that came out a few months ago, there's not enough evidence to say, yes, Naledi were burying their dead at this point in time. Okay. So funeral rights is looking more like funeral wrongs. Nice. Maybe. The next thing was rock art.

How are scientists feeling about this? Okay. Okay. So to start with the title of the rock art preprint is, it's pretty catchy. Are you ready for this? I'm ready. Quote, 241,000 to 335,000 years old rock engravings made by Homo naledi in the Rising Star Cave System, South Africa.

Like, that's the title, right? Right, full stop, no question mark. Just full stop. No question mark. Got it. And the thing you need to know about rock art is it's notoriously difficult to date. And when you speak to rock art experts, they kind of rely on scientific tricks to get, like, even the most basic sense of how old a piece of rock art is.

Oh, okay. Like, my favorite example comes from the Kimberley in northwestern Australia, where sometimes you find fossilised wasps' nests that have been built over the top of rock art. And so what the scientists do is they go and they date the fossilised wasp nest and then they can say, well, the art that's underneath it is at least older than that nest. Oh, that's so cool.

Because I never thought about this because in this case, it's just scratches on the rock. So you can't date the rock, obviously, because that is going to be way older. Yeah, there's nothing specifically to date. I'd never thought about that. Right. So how do they try and date?

Exactly. It's super tricky to do. And so it's like, yeah, when this nothing specifically to date. I'd never thought about that. Right. So how did they find date? Exactly, exactly. It's super tricky to do. And so it's like, yeah, when this burger paper comes out with a date range right there in the title, one of the first questions that a lot of scientists had was like, where does that date range come from? Yeah, so where did they get these dates from? Okay, so like one of the key bits of evidence that Lee has for arguing that it was Naledi that made the scratches in this cave is that his team knows everyone who's entered this like deep, difficult to access section of the Rising Star cave system.

Humans haven't entered this space. Other than the 47 people, and that's why we list everyone's name in the back of the book and in the research papers, we have no evidence that humans have ever entered there. And because of the context, because there are burials beneath them, because they mark these spaces, we have said we attribute these to Homo naledi. Wait, how could he possibly know who's been in that cave system? Exactly.

Exactly right. And so when this paper came out, a lot of the scientists who have been publicly commenting on this, a lot of people I've spoken to are saying, like, how could Leonie's team know absolutely everyone that's been in this cave system from 240,000 years ago to a couple of decades ago, right? But more than that, there's actually evidence that other people have access to this section of Rising Star. Oh, no. Wait, so this, it could be like, the headline of that paper could have been, 50 years ago, rock engravings made by Emily. Okay, so remember there were those explorers

who first found the Dental Eddie chamber and took photos of the bones that showed them to Lee? Yes, yes. Well, when they found those bones, they also found something else deep inside this cave system. They found survey markers. Now, survey markers are a piece of equipment that are used by cavers when they're, I don't know, like caving.

Right, okay. One of the explorers wrote this report where he says, we can't really figure out who left these survey markers there. They weren't theirs and they didn't seem to belong to anyone that Lee had listed in the book or in the research paper. Whoa. So someone was in that. Emily could have done it. Emily might have been there.

So we went back to Liam. We asked him about the survey markers, but he insists that they've got to have been from one of the people that were listed on his list. What? I mean, I'm almost surprised that he didn't think homo to let him put the survey markers in there. Look, you and Andy Harries have a very similar sense of humour.

It's almost impossible to sit there and say, right, well, this is, you know, 50 years old or this is 300,000 years old. There's no way that you can say that this is Homo naledi that made this because it's just, it's in the same cave site as Homo naledi is. I mean, that's like turning around and saying, we found these survey markers in the chamber with Homan O'Leddy. They must have been made by Homan O'Leddy,

not by cavers that went in there in the 1960s. I mean, it's essentially the same sort of thing. All right. All right, Eddie, I'll buy you a beer. Look, there's plenty of interesting comments around this. Probably my favorite peer review comment about this is, quote, what is clear is that the scratches could have easily been made by a modern-day farmer 50 years ago as homeowner Leti about 335,000 years ago.

Oh, okay. But there's one more question that we have to ask about rock art, and that is whether these engravings were made by anyone at all. What do you mean? Right, so remember when I introduced Andy, I said that he worked just down the road from Rising Star? Yeah. So I work at the site of Dremolin,

which is, oh, I'd say about eight kilometres from Rising Star, so it's not very far. It's in the same geological Malmarni dolomite formation. So what he means there is like the massive chunk of rock that all of these caves and all of the fossils in the caves are found in is known as the Malmarni subgroup. And it's made of a type of rock called dolomite. You know, I looked at the rock art and my initial reaction was well that looks like lots of patterns that you see naturally on the

dolomite in south africa anyway so the maomani has this tendency to create quite abstract looking patterns in the way that it dissolves in the way that it weathers. And so, okay, well, the first thing is can we be confident that what's being called rock art is not just that? Ooh, so he's saying there's something about the way the rocks form and change that can sometimes look like hashtags and equilateral triangles? It's a patterning that he calls elephant skin because it looks like the

kind of skin of an elephant. He actually shared a photo. Do you want me to show you the photo? Just one sec. There you go. Okay. Oh, oh shoot. So that is natural, what you just sent me. Yeah, that happens all around the region. And that was Andy's first impression. Oh, man, that looked exactly like what on the doco they said that had to be, like, unnatural, that had to have been carved in by someone or something, you know. Whoa.

Now, look, to be fair, Andy taking a photo of some naturally occurring erosion, like that's not scientific either, right? But once again, like when I spoke to one of the reviewers on the rock art preprint and like other experts in the space, they were all of the opinion that the evidence as it currently stands doesn't support Naledi making rock art at Rising Star. I think one reviewer summed it up best when they wrote, quote, the claims relating to artificiality, age, and authorship made here seem entangled, premature and speculative, end quote. Okay.

Okay. I mean, it's interesting. I would have been a little bit for Lee Berger on this one because it is an odd thing to do, go down in a cave and make some weird-ass scratches. But what Berger reckons are is rock art and this natural formation does look really similar. And so I definitely want to see some data as to why Lee didn't think they were the same thing. Yeah, exactly right. And we went back to Lee about this and he told us that he can see

places where the marks supposedly made by Naledi cross over natural features in the wall and they think that the markings look different to that natural stuff. And so, you know, like maybe we'll see some of this evidence laid out in future papers from their team. Mm-hmm. Okay. Huh. So where does this leave us?

Cave of bones? Cave of insufficient evidence? I guess there's a reason the doco was called unknown cave of bones because we don't know anything. I feel that. I feel that. By the way, we did reach out to Netflix a few times to ask them about all of this, but they didn't get back to us.

And Lee says that they're currently working on revisions to the preprints, but we don't know when those will drop. But look, there's a lot of the science that's being debated around this discovery. We haven't included absolutely everything that's in contention. Like there's talk about whether Naledi was using fire in the cave system. There's even a debate around whether like the structural layout of the cave system is the same today as it was at the time of Naledi. There's so much that's being debated. Like there was an original cut of this episode that ran almost as long as the film itself,

just trying to cover all of these controversies. But there is a really interesting nuance to the debate as well. And it's that all of these scientists who are criticising Berger's work, none of them are actually saying there's no way that Naledi could have done any of this, right? Like, the scientists are open to the idea that, like, a small-brained hominin could have been any of this, right? Like the scientists are open to the idea that like a small-brained hominin could have been burying its dead

and could have been scratching marks on the wall. And a lot of them are actually excited by that possibility. I mean, I personally think that we don't give our ancestors enough credit in terms of the things that they probably could do. So I'm entirely open to the idea that smaller-brained hominids could have done more complex behavior than we were expecting. That's the frustrating thing about all this.

Homo leade is amazing. It's an amazing series of fossils in an amazingly interesting context. But also, you know, we've got to have some form of evidence about it. I mean, that was, I think, most people's issue. I mean, I think most scientists, you know, are going to be perfectly open to the idea that, you know, that these things could be. But most scientists would say that we have a responsibility before we go out and do press releases out in the public or do documentaries or book releases,

that we don't just sort of say could be you know if i was going to nail down like one moment of frustration that everyone who's criticizing burger felt it's that the netflix film had been made and was scheduled for release before anyone had had an opportunity to stress test that work and to test the evidence. And that was the real frustration. And so in the interview, I asked Lee if now that they're kind of over that hump, whether he thought that he went too soon with the Netflix documentary. I love that this story is so much about the process of science. I love the scientific process and the iterative, nothing's ever certain.

Even just getting into the details with you there, there's still stuff you're figuring out. This is very much a working process. There's uncertainties there. And so I think a big question that a lot of people have had is like with those uncertainties still in play, like do you think it was too early to go to the Netflix film? Because the Netflix film also doesn't address any of those uncertainties. Yeah, no, I don't. I see the Netflix film as following the process of science.

I mean, you know, because the alternative to that is people don't actually want to see what happened. But the people who watch the film who don't have a scientific background or maybe don't read the peer reviews, to them, it's going to appear as if like, oh, well, all of this is locked in. Like this is... Well, you know, again, I mean, speaking very strongly to that, you know, that's not the way science works. There is no truth at the end of that. The process will continue and we're just putting it out there. But, you know, I'm not apologetic about that

and no one will ever get me to be. We're just putting it out there. I guess it's just like hit a nerve with me because we just keep seeing the fallout of what happens when you put half-baked ideas, I won't call it science, I'll call it half-baked ideas, out into the public. Scientists fight about them and the public thinks,

oh, scientists don't know anything. Nothing's real. Let's just follow snake oil salesmen over there. My most generous reading is that this team and Lee Berger just fell in love with the romance of what they uncovered here, which you can really tell from the documentary. You know, that's why it's a fascinating documentary, the idea that there were these hominins walking around

doing this cool, cool stuff thousands and thousands of years before we did. It's so cool. And they fell in love with that. And then they were like, oh, and that's rock art. And that's a burial. And they fell in love with that. And then they didn't do the work to prove it, to prove that's actually what's there. And so should there be a chart-topping film that millions of people are watching based on something where the science is still out?

Like, I think that's the question at the heart of this story. You know what the doco should have been called? It should have been unknown. Rock makes rock art. Billion year old rock making rock art. Maybe it'd be like slow TV. You could slowly watch the Malmarnie Dolomite erodes. We're live streaming the erosion, people. Now that I would watch. Thanks, Joel. Thanks, Wendy.

That's sidespaces. Ring, ring, ring, ring. Do we still do the rings, Joel? I mean, you're right here. Can we just do citations? I'm not, yeah. Like, I don't know where my phone is. Do we still do the rings, Joel? I mean, you're right here. Can we just do citations? I'm not, yeah. Like, I don't know where my phone is. Can we just do them here?

Yeah, how many citations in this week's episode? Look, like one thing I will tell you is that we had more citations for this episode than Lee and his team had for their burial paper. I really hope Jamie doesn't mail us. So how many citations are there? That's something. We had 74 citations today. 74. And if people want to see these citations, where should they go? If they check the show notes in their podcast app of choice, they can find the link to our transcripts and our transcript is fully annotated. So lots of juicy extra info for you to get into. Cool. Bye. Bye.

Science Versus is a Spotify Studios original. Listen to us for free on Spotify or wherever you get your podcasts. And you can follow us on Spotify. And if you want to know when we have new episodes coming out, then just tap the bell icon. So when a new episode comes out, you will be the first to know about it. I mean, we will be the first to know about it, but very soon after you're going to find out. If you like our show, please give us a five star review on whatever podcatcher you're listening on. This episode was produced by Joel Werner, with help from me, Wendy Zuckerman, Michelle Dang,

Rose Rimler and Nick Delrose. We're edited by Blythe Terrell. Fact-checking by Diane Kelly. Mix and sound design by Bumi Hidaka. Music written by Bobby Lord, Emma Munger, Peter Leonard, Zoe Wiley and Bumi Hidaka. Thanks to all of the researchers that we spoke to for this episode, including Dr. Bridget Alex, Professor Michael Petraglia, Dr. Kimberley Folk, Dr. Sven Usman, Dr. Elizabeth Grace Veitch, Dr. Flink Dibble, Professor Tim White and Professor Bernard

Wood. And a big thanks to Lindsay Cherner, Jack Weinstein, Katie Vines, the Zuckerman family and Joseph Lavelle Wilson. I'm Wendy Zuckerman. Back to you next time.