Science Friday - Biohybrid Robots, Neanderthal Art. Feb 23, 2018, Part 2

Episode Date: February 23, 2018

A group of engineers are building softer, squishier robots—ones you might knowingly invite into your home to hang out. Instead of sporting bodies of rigid plastic and metal, biohybrid robots often consist of 3D-printed scaffolds laced with lab-grown muscles, sourced from the cells of mice, insects, and even sea slugs. Some "bio-bots" can even heal themselves after an injury, and get back to work. A roundup of engineers talk about the growing fleet of biohybrid robots. Plus, since the first fossil finds in the 19th century, many have considered Neanderthals, a “sister species” of Homo sapiens, as a primitive species. Their reputation stands as unsophisticated and brutish—and not artistic. Now, new uranium dating of art in Spanish caves turns up a number that suggests they were painted by Neanderthals. And if it’s true, what does art have to do with complex thought? Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. Does the name Big Dog ring a bell? It's the name of that horse-sized robot from the company Boston Dynamics. You know what I'm talking about. It's that creepy robot that can jog and trot and climb over rubble, slip on ice and get right back up again. Maybe you've seen it on YouTube. It's kind of scary. Well, the company's newest creation, the Spot Mini, is smaller, about the size of a Rottweiler. And it can open doors by itself. And this week we watch. with some concern, a new video in which the Spot Mini fends off a human handler trying to interfere with the task at hand, just like a mischievous dog would. These robots are obviously inspired by the movements and mechanics and behaviors of real four-legged creatures. But they're made of rigid metal and plastic. Well, why not take inspiration from the whole animal? Try to recreate its muscles and its nerves, too.

Make a robot that's partly a living thing. That's the goal of my next guests, who create so-called bio-hybrid robots, soft robots, squishy, flexible things that may someday be a whole new lineage in the robotic family tree and may be a bit more lovable, too. Rita Raymond is a fellow at Massachusetts Institute of Technology in Cambridge. Welcome back, Rita. Thank you, Ira. It's great to be back. Vicki Webster Wood is a post-doctoral. Research Fellow at Case Western Reserve University.

And Cleveland, welcome, Vicki. Hi, IRIS. Thanks for having me. You're welcome. Barry Trimmer is editor-in-chief of the journal Soft Robotics and Professor of Biology at Tufts University. Welcome to Science Friday, Professor. Hi, Ira, thank you very much for having me on the show. Reader, let me start with you. Last time we had you on a couple of years back, the idea was, can you make artificial muscles walk? But now I understand you've been able to thread neurons in there, too? Activate the muscles more like what happens in our bodies?

Absolutely, yes. So we initially started with muscle because we thought, you know, walking is kind of this really easy thing for people to see. But once we got the walking down, we thought, well, it would be really nice to be able to control that walking in a new or interesting way. So we worked on controlling the biobots walking with light. And then after that, we move to adding different types of cells, neurons, where we tell the neurons to go on or off and then watch the biobot respond to that cue. So this thing is basically a robot, but it does what you tell it to do, and it's made out of real flesh, real tissue?

Yes. I think if you broadly define a robot as anything that senses, processes, and responds to a signal in real time, then a biobot is really something that uses biological materials to do one or all of those things. Now, Dr. Webster, what I understand that you've also done work on integrating neurons into biobots muscle circuits. What is the advantage of doing that instead of just zapping the muscle with electricity? Absolutely. So I work a lot with tissues from a sea slug.

It's a very robust material. And what we can do with that system is we can actually isolate whole muscle tissue along with the nerves that innervate the muscle and the clusters of neurons that feel. into those nerves. And what we've seen is that if you stimulate the muscle directly, electrically, the muscle fatigues very quickly. However, if you stimulate the muscle via the natural neural circuitry, whether that be via the nerve itself or by inducing natural motor patterns in the clusters of neurons, we see much better performance in the muscle when we stimulate via that natural circuitry

with better stimulation from the nerve and even better stimulation yet when we stimulate the neurons themselves, both in terms of the fatigue of the muscle and the output of the muscles. So by using that circuitry, we can have more robust, more powerful robots. So the nerve knows how to do it better is what you're saying. Essentially, yes. Do you have to follow your robot around squirting it with neurotransmitters, keeping it wet, you know, keeping it alive, with the liquids we all need in our bodies? Right now our robots are running around in petri dishes.

in a liquid environment that has the right salt balances and glucose to provide energy to the robot. And we are stimulating it by just putting a little drop of chemical on the clusters of neurons. In the future, we may be able to incorporate microfluidic systems that would basically spit out a little bit of chemical at the right time for the action we want from the robot.

Or we may be able to incorporate sensory cells and actually have the robot be stimulated by external sensory. cues like a chemical gradient in the liquid. Were you serious when you said you had little petri dishes running around? Is that literally what's happening? No, the robots are running around in the petri dishes. But we can see, oh, I see them. The dishes aren't running around.

Okay. No, no, it's like having a little aquarium for your robot. Oh, yeah, that's what I was wondering. I keep them all, you know, bathe in what they need. Dr. Trimmer, what's the problem with regular hard-bodied robots? What advantage does real flesh or soft bodies give them over, you know, the kind of robots we're used to? Well, I don't want to be sounding critical of our current robots. I actually think that they're truly remarkable.

And the things that you mentioned earlier on about the Boston Dynamics robots, it's a tour de force. I mean, it truly is amazing what they've been able to do. But there are many, many tasks and things that we would like to have help with. with that traditional hard robots aren't particularly good at doing. If you imagine having robots in the home or the office or the hospital, you'd like them to be pretty safe. And you don't want them just control safe. In other words, you don't want them to be safe as long as they're controlled, but not safe when they're uncontrolled. And current hard robots are controlled. In other

words, we only want to put people around them as long as they're in control. I think by trying to incorporate soft materials and biomaterials into robots, we can create machines that actually will be completely safe, intrinsically safe. So even if the control systems fail, they're not going to do very much harm. So that's one aspect. I think the other ones that we need to touch on is that soft materials and biomaterials let the robots operate in lots of ways that our traditional robots can't. We can get them to change shape and size. We can get them to wiggle through a pile of debris that might have fallen during an emergency situation and find people. We can have them work in the delicate canopy of a forest or in a field.

And those sorts of things are much, much easier to imagine with a robot that's, more like a biological specimen that actually isn't going to damage the world around it. Interesting. 8447-24-8255 is our number. 844-8-24-8255. You can also send us a tweet at SciFRI. Rita, is skeletal muscle also a strong building tool, more power, more force for its size than any other types of things you could build with? Absolutely.

So I'm actually a mechanical engineer by training. And when we think about the synthetic actuators that we have available to us and then compare it with what nature has evolved to do all of its force production and locomotion, which is skeletal muscle, I mean, it's just the phenomenal how much power it can generate from such a small size and how efficiently muscle can do it. So when we're thinking about designing the next generation of robots and systems, sure, we could go in and look at synthetic actuators, but if we have something that we know works better,

we should absolutely go for that, right? Yeah. Dr. Websterwood, I, you know, I've been studying cells for many years. And I remember the first time I studied cardiac cells. I discovered that if you take a cardiac cell and you put it in a petri dish, it'll start to beat on its own. And then, you know, can you use that kind of action to create a mechanical device or a bio-hybrid robot?

That sort of trait of a muscle or sort of trait of what the living flesh is? Absolutely. And there are some very interesting examples of these biohybrid robots that use cardiac muscle as the actuator. Like you said, when you think about cardiac muscle, you think about a heart beating spontaneously. And we do see that with the cells in the dish. One example recently that actually I think is a good example of combining bioinspiration and biohibrid robots is actually a group under the direction of Dr. Kevin Kitt Parker developed a jellyfish-inspired biohybrid robot where they actually studied the structure of the

musculature in the jellyfish and reproduced that on a synthetic device by microcontact printing proteins that heart cells would like to attach to. And then when the heart cells attach, they spread out and follow these proteins. and so you can basically design a actuator that will self-assemble so that all the heart muscles are pulling together in one direction. And in this way, they were actually able to capture a lot of the locomotion similarities that they saw in the real jellyfish. And can you actually make them small enough, I mean,

that they could go to work inside the body to do something useful? Potentially. I think one of the great applications that a number of researchers in the field are talking about is creating very small-scale bio-hybrid robots or even completely organic robots, which we like to call organobots, that you could make out of, say, biological polymers that are naturally occurring in the body.

And then you could deploy the robot into either the digestive system or the vascular system and have it provide targeted drug delivery or potentially even deploy and provide mechanical or chemical cues to an area to say, strengthen a vessel wall. I have a tweet in from Mike in Ohio asks, if these robots are biological,

can they get sick? I could maybe comment a little bit on that. One thing that we really like to talk about when we're thinking about biological materials, we think we're talking about, you know, soft materials, that's great. But the really interesting thing about building biological materials is that they're constantly sensing

and adapting to their environments, right? So that could be both negative cues like getting sick or, as I've studied, how we damage biobots and see them get hurt. But the great thing about the fact that they're biological is that then they can sense that damage or that sickness and respond to it in a positive way. So yes, they can get sick, but we also hope that they can get better. So if you put biobots into the water system and it detects pollution and starts getting sick from some sort of biohazard, it could say, hey, there's something in here. be alerted. Exactly. Yeah.

And I, if I might add to that as well, of course, this idea of using biopolymers and living cells to make robots is what we might call green technology. These robots don't cost a lot to make. We're growing them instead of, you know, big factories with high temperature and lots of energy expenditure. And, you know, one of the wonderful things would be to recycle them. All these materials would be biodegradable, and you rebuild your robot from the generation that has just given up the ghost. All right, hold that thought because we're not giving up the ghost on this topic.

We're going to take a break, and when we come right back, we'll talk more about biobots after the break. Stay with us. This is Science Friday. I'm Ira Plato. We're talking about bio-hybrid robots made of real muscles and nerves and attached to mechanical stuff with my guests. Rita Raymond of MIT, Vicki Webster Wood of Case Western Reserve, and Barry Trimmer of Tufts, our number 844-8255. I have some interesting calls.

Let's go to the phones. Let's go to Becky and Norman, Oklahoma. Hi, Becky. Hi, thanks for taking my call. Go for it. I have a question about the ethics of using the live tissue, and is this a respectful use of that living? tissue and how is it treated in that way?

And because I understand that it's put in a pile to decompose afterwards. Could you explain how that's handled? Okay, thanks for the call. Yeah. If I might try and have a stab at that one, I completely understand that using living cells of any sort brings a lot of ethical considerations and we really have to think about it carefully. You know, a lot of our biomedical needs are going to be driven by using vertebrate cells because they're more likely to be more compatible with medical issues.

But that doesn't necessarily constrain us when we're trying to build other types of robots. And, in fact, myself and Vicky are actually both working on non-vertebrate cells. in our case we take cells out of insects and grow them and I think that as long as we're not trying to actually build and grow a brain as such we can have a nervous system of some sort but if we're not trying to actually grow a brain or reproductive system we're not trying to grow animals we're trying to build an engineered device that is made of living cells and I think that we can all you know agree there are some ethical issues we need to need to talk about in that, and that needs to be dealt with. We need to really get on top of that before this technology starts to take off in a more commercial sense. But there are ways in which we can deal with those ethical issues, I think, with the selection of the tissues that we use to build the robots. Rito, you have any, Rito or Vicki? Any kind of? Yeah, I'd like to just add to that a little bit. With the work we're doing with invertebrates, it's very possible that, as we

move this technology forward, we may be able to essentially farm the cells. You know, in the real aquatic environment, the sea slugs produce these egg chains. And we may be able to actually get cells from the egg chains rather than needing to work with adult animals. And then also looking at the applications we're looking at, when we're working with these types of bio-hybrid robots, and they're completely biocompatible, they're completely organic even, if we deploy them into a sensitive ecosystem and the robots are able to perform monitoring tasks in that environment, we'll be able to more conscientiously monitor and look after

these sensitive environments. And then if the robot breaks down, it's not leaching heavy metals out into the water. If a fish eats it, it's not going to hurt the fish. And so I think there's a balance there in our stewardship of the environment with these robots. Speaking of which, if the robot gets injured, you know, let's say fish grabs it and it gets away, is it able to heal itself while it's still in the wild? Do you? Absolutely.

So I would say right now where the technology is, we've made these skeletal muscle-powered biobots. So they have a flexible skeleton and they have this skeletal muscle that goes around them. And every time the muscle contracts, the skeleton moves and the robot walks. So we went in and we cut the muscle with a little pair of scissors, and then the biobot was hurt, and it couldn't walk anymore. And now if that were a traditional robotic device made of synthetic materials, that would be kind of the end of the road, right? You just have to scrap that robot and start over. But we thought, okay, what if I could just go in and put some sort of glue? And that glue, you know, we really kind of optimize the concentration and composition of that.

We said, okay, maybe it needs a few cells. maybe it needs some proteins and growth factors. We took inspiration from how muscle heals inside the body, and we tried to recreate that on the bot. And what we saw is that because of these biological materials and cues, the biobot would heal and within two days start walking again, producing the same kinds of forces and walking at the same speeds as before.

So I wouldn't really call that self-healing quite yet. I think it's healing. But if, you know, at a later, date we start thinking about can we incorporate a vascular network or someplace where the biobot can kind of store this healing glue in case it gets hurt and then release it once it's hurt, then you could call that sort of behavior closer to self-healing. I guess you had an experiment that come up with this poultice, so to speak, to help the yeah, it was a long process. But, you know, it was an experiment, but also it was kind of easy

because nature had already figured out how to do the healing. I just had to understand it and try to recreate it in the lab. With lots of tweets coming in, lots of phone calls. Let me go to this interesting tweet that I was thinking about this a while back from Sean who says, could biobots be used to replace damaged muscles and nerves in the human body? Absolutely. I mean, I think that's something that we're trying to do right now where there's an established field of tissue engineering where you think about creating new tissues or organs

and replacing disease or damaged tissue or organs in the body. body. And biobots have kind of been evolving in parallel, but a lot of the lessons that we've been learning about how to make muscle or how to make neurons could be applied back in medicine as well. Can you give me a specific way that might show up first, for example? So one example could be, you know, any sort of disease where you have some sort of muscle degeneration or perhaps like a volumetric muscle loss injury, something where it's so much of the muscle that the body can't heal itself, could we then go in and put some of our tissue engineered muscle in place and see a person be able to recover function of that limb?

Does somebody want to jump in there? Yeah, I mean, I just like to add on that, too, that the robots really provide us with a interesting laboratory test platform to develop all of these techniques to then apply to actual clinical applications, right? Oftentimes you hear about these lab on a chip type systems, and that's where usually people are growing tissues in like a single layer on a chip. But if we want to develop techniques for, as Rita said, replacing, say, volumetric muscle loss injuries, then we really want to be testing those techniques in a system where we've got a bulk tissue that's actually performing a task like it would in the body.

Yeah, well, could you actually make prosthetics out of these, you know? I like to think so, yeah. One of my long-term goals is definitely to pursue this idea of biohybrid prosthetics, where in the short term, that may be, you know, replacing a chunk of muscle and a volumetric muscle loss injury. But in the long term, we may be actually able to consider building large-scale functional tissues into kind of the more traditional prosthetic shells that people are familiar with in order to give patients back a better organic feel to their use of their limbs.

I have a call from Andre in Pittsburgh. Aye, welcome to Science Friday. Hi, Ira. Thank you. Love the show. Thanks for making science so fun and interesting every Friday. You're welcome. I have a question.

So I run a facility in Pittsburgh that does hands-on biotech experimentation with kids and youth. And, you know, this sounds like this would be a really, really awesome experiment to implement in the lab. So I'm calling to find out how feasible do you think it would be to do a small-scale experiment like this to sort of illustrate this to you around the city and to get them really excited about these micro-biobots. Is there a do-it-yourself home kit, yeah, to make... I actually would love to comment on this. Yes, go ahead.

So that was my idea a couple years ago when I was on the show, and we got a lot of feedback. there was a lot of people saying, I want to build my own biobot. So I started thinking about how to make a kit to do that. And I actually started my own undergraduate class at the University of Illinois, where I was at the time. And that's currently in its fourth year where bioengineering undergraduates who are used to working with cells start to learn how to design and build and test their own biobots. So now that we have that in place, I think it would be great to think about bringing it to an even younger audience where maybe you're not designing and building everything from scratch, but we give you a biobot, we ship it out to you, and maybe you can assemble a couple parts together, and you can see kind of how it moves or walks around. Really, the only requirements there would be that you have a warm environment and a petri dish with that sort of sugar water that the biobots need to walk. So that would be great. That brings me to my, you actually touched on my next question,

and that is, and let me send this to Barry, are the biobots also an opportunity to think about different methods of fueling our machines? You know, we run on sugar and fat, but these robots could they metabolize food for their energy instead of burning oil or having lithium ion batteries? I think, Ira, that's really one of the huge advantages of trying to use a biologically based actuator instead of, you know, the traditional engineered motors. Right now, the energy density of lithium-mine batteries is pretty good, but it's nowhere near as good as gasoline or fat.

And, you know, I don't think you'd want to have robots working around the home that are powered by gasoline engines. When you think about it, people sitting in a lecture hall are sitting there and they're just casually burning, their fat and sugar fuels with no danger to the people around them. So you can imagine that a muscle-powered robot, and we're talking now about something that's quite large, it's not just a little tiny microbot, but a muscle-powered robot would essentially be the same as we are, and that we'd provide it with a sugar infusion, or maybe

it's got its own onboard fat, and if we design the system well, it simply, you know, it simply, uses that as its fuel source. And that means that it can operate for days and days and days without being refueled. And of course, that isn't possible with most current untethered robots. They really run through their batteries pretty quickly. So I think, yes, it's a great vision. It also gets us away from, as Vicky and Richard have already said, that it gets us away from a lot of the toxicity and dangers of some of our current technology. And if you have a robot that has a certain percentage, a large percentage of it made out of flesh, muscle, whatever, doesn't it also do two things?

Doesn't it first humanize a robot and make it be less threatening to people who figure, well, if it's, you know, these giant metallic robots go out of control? I can't do anything, but this one seems kind of vulnerable. if I know where to hit it with a stick, you know. Well, I think it's absolutely true that one of the advantages, perhaps, of a soft robot technology using biological materials is that we will have a different relationship with the robots. There are lots and lots of interesting social questions about that, about how that would be implemented.

But as I mentioned earlier, my goal, even though... Ironically, I'm a neurobiologist by training, and you'd think I'd be in favor of growing brains. I don't think that we need to put brains into these robots. I think they will have biological components. They will have muscle. But I think we'd be best advised to be controlling them with microcontrollers and computer chips. Certainly in the near future, that's the way it's going to be. So they would be humanized, but not human.

This is Science Friday from PRI, Public Radio. International. Talking with three real humans on the line, Rita Ryman of MIT, Vicki Webster, Wood of Case Western, and Barry Trimmer of Tuts. Where do you see this, Rita? Where do you see, you know, in the macro world, how this is all going to play out? So I think, kind of touching on this point of humanization, I want to emphasize, again, I think our goal is not really to create any sort of living machine or robot, right?

The real goal is to say for thousands of years, we've been building with these materials like metal and wood, and they aren't sensing or adapting to their environment in any way. So when we have a dynamic problem, we don't have these dynamic solutions. We have these very static solutions, then we then have to go in and change every few minutes or hours or weeks. And so what I think and what I hope other people in the field think is how can we just expand the set of materials or the tools that engineers have to work with so that they also include these responsive biological materials. So when you're building a machine to address a problem, not only do you have access to wood and metal and ceramics, but you also have access to these kinds of biological materials. So that's kind of how I think I would love to see people using these sorts of just an additional thing that they have in their toolkit. So if they're thinking about building a robot, okay, maybe I need an actuator.

I was going to use this synthetic actuator, but instead I'm going to use this muscle instead. Because nature has figured that out already, right? Exactly. It's come up with a really good device for you. Why not use it? That's very true. And not only that, it's self-assembles. it starts off with a cell and a bunch of chemicals,

and it constructs the entire piece of tissue with all of its incredible complexity without us having to intervene. And I think the idea of growing robots without actually fabricating them is a very, very attractive one. That's an interesting way that you put it, growing them. How large, theoretically, could you grow the muscle, the tissue, whatever you need in the robot? and, you know, what are the limits, practically, what are the limits, practically speaking, Barry, on this? I think that we're still at very early stages right now, which is why we're all working with relatively small amounts of tissue. There are challenges, particularly with using vertebrate tissue where we need to have a vasculature.

We need to control the environment of the cells quite carefully. a little less of a problem with that when we're using insect tissues because they're used to living in an open circulatory system, and so they tend to be much tougher. So some of the limits on how big they get depends on how well we can construct those scaffolds on which the muscle needs to grow and then survive. In my opinion, if we learn enough about how the size and shape and the nature of a tissue is actually developed in the living animal in the first place, then we should be able to engineer it. So when you think about it, we have muscles in insects as small as, you know, less than a millimeter, and we have muscles in whales as big as cars.

And, you know, so tissue knows how to do it. it. We don't know how to do it yet, but the limit is that we don't know how to do it, and we're trying to find that out. Okay, no better way to end this discussion on that note. Barry Trimmer is editor-in-chief of the journal Soft Robotics, Professor of Biology at Tufts in Massachusetts.

Ficki Webster Wood, postdoctoral research fellow at Case Western Reserve in Ohio and Cleveland, and Rita Ryman is post-doctoral fellow at MIT in Cambridge, Massachusetts. Thank you all for joining us this hour. Thank you for having us. And we have photos and videos of the bots that they were talking about on our site at ScienceFriday.com slash biobot.

We're going to take a break and come back and talk about cave paintings in Spain and Neanderthals. Were they artists too? We'll talk about it right after this break. This is Science Friday. I'm Ira Flito. Our ideas about Neanderthals have come a long way in the last few decades. first thought to be thick-browed strangers, we have learned that they were genetically much like us

and even interbred with humans during a period when both Neanderthals and modern humans lived together in Europe. And there are still Neanderthal traces in the genes of anyone whose ancestry lies outside sub-Saharan Africa. But what were they like? And why didn't they survive? Well, while we did.

Some theories still point to brains. The word Neanderthal is still used as a slur to insult someone's intelligence or sophistication. And while archaeologists can point to pigmented shell jewelry as a sign of rising abstract thought in our ancestors, there's less evidence that Neanderthals thoughts symbolically or made art. So that's changing now because new research makes exactly that claim for Neanderthals. A team of scientists using uranium dating of tiny calcels. crusts over cave paintings in Spain to say that these paintings had to be older than 60,000 years, a time when so far there's no evidence of modern humans living in Spain. So the conclusion,

well, the Neanderthals were responsible for handprints and red lines painted in ochre. And the conclusion from that, they thought abstractively and symbolically just like us. And that work is published in the journal Science. Here to explain some of the new research is Dr. Christopher Standish, a co-author on that paper and an archaeologist at the University of Southampton in the UK, and we have pictures of the cave paintings in question up on our website at Science Friday.com slash cave art. Welcome to Science Friday. Hi, thank you.

You're welcome. So how sophisticated is the art in these caves? Are we talking about the horses, you know, we've seen in other caves around, or is something much simpler? Yeah, no, it's slightly different to the sort of the more famous images that you see from sites like Chauvel in Lascau and Outamira of the sort of polychrome animals,

bison, horses and things. They're generally, well, non-figurative art is made from red pigment, things like linear forms. One of them is a, it's called a scolera form, so it's a ladder-like shape, part of a more complex panel, hand stencils, and general

sort of patches of pigment on stalgmitic formations. Give us an idea of how you dated the paintings. You were looking at crusts that had formed on top of them. Yeah, absolutely. So these crusts are made from kerosene carbonate, and they're essentially tiny spele of them, so secondary carbonate formations along the lines of stalagmites and stalactites. So they form in the same way.

Rainwater passes through the soil profile above a cave, This gets enriched in carbon dioxide, so it becomes a weak acid. And when it percolates through the limestone below, it dissolves up small amounts of calcium. When this water enters the cave below, the carbon dioxide is released, and this leads to the precipitation of calcite, and you get the formations of these spilisemes. Now, it's possible to use uranium thorium to date spedithems. This has been done for decades now. It's a technique that's used significantly by climate scientists

when they're looking at elemental differences in stalobites. And that's because the uranium and thorium have different solubilities. So uranium is very soluble, which means it gets dissolved up by these waters, whereas thorium is insoluble, so it isn't. The 238 uranium, which is the isotope at the beginning of the decay chain, we're interested in, has a half-life of about four and a half billion years. And when the calcite forms, it's sort of a clock is essentially beginning. And by measuring the amounts of 238 uranium, 230 thorium and one of the intermediary isotopes,

we can calculate the age of the spilothem formation. And just like stalagymites and stalactites grow, you get these small little crusts forming on top of pigment. So if we date those, we know that the art underneath must be older. We're getting a minimum age for the art. What is the minimum age are getting? So for each three of these sites, we've got minimum ages of 64,000 years or older. Wow.

And indeed, there's no maximum age yet? Well, so one of them, we have managed to get a couple of maximum ages. This is a lot more difficult. It's quite a rare occurrence because it relies on, the art being applied onto a spilious m, so sort of being used as a canvas. And the only way we can sample this is generally when they fractured naturally, and so we can get in from the side, because we never sampled through the pigment. And so what maximum age did you come up with?

Well, this was for a different motif to the ones that we have, the minimum age of 64,000 years. So there is one motif that we can. date to between 45 and 48,000 years ago, so that's a minimum and a maximum. Unfortunately, there's no maximum for the motives we've dated to even earlier. So tell us why 60,000 years is such an important number for the Neanderthals. Yeah, well, current evidence for the arrival of Fomo sapiens in Spain places them around 42,000 years ago in the north. Now there's various estimates

sort of one or two thousand years either side of that but it's essentially around 42,000 years in the south of Spain this is probably a little bit later recent work down in the southeast suggests about 37,000 years

so there's no evidence of homo sapiens before 42,000 years ago anywhere in Iberia so the fact that this art is is being produced prior to 64,000 years ago means that it's a different hominin group that must have been creating it.

And in this case, the most likely scenario is it's Neanderthals. Wow. Is age all we need to decide that the Neanderthals made these paintings? Sorry, can you repeat that? Is the age? All we need to secure the idea that Neanderthals made these paintings? Well, I mean, it's about the best we can do. There's no other way to link the art to a particular type of human.

They're notoriously difficult to date as they are already. So we just have to work out the age of the art and then compare it to the archaeological record to see which groups were living there. And how is this finding being accepted? People say we need more. You've got to do another one? This is so fantastic. We need some more evidence?

Well, I suppose it's hard to see. We'll have to wait to see until the dust settles. but I mean a lot of people are acting very positively about it. We have been holding on to these old dates for a little while now. The first one was probably collected a couple of years ago, but we waited until we found some sort of supporting evidence to go with it. So it's not like we've just got one date saying this. We've got three samples from three different caves,

and they're all made up from individual sub-samples themselves. So we've waited for a decent body of evidence to help support our interpretations. Yeah, that's good. That's very wise. I want to bring on another archaeologist not involved in this work. Dr. Christian Tryan, Associate Professor of Anthropology at Harvard. Welcome, Dr. Triand. Hello, and thank you for having me on.

Oh, you're welcome. Tell us how well this Neanderthals made cave art fits with everything else we've been learning about how they lived and how smart they might have been? Yeah, I mean, it's a nice part of the picture. I mean, we're constantly learning more about Neanderthals, what we think they're doing, what we think they were capable of. And this sort of adds an extra wrinkle, and that, you know, if Neanderthals are making these things that we call art,

that implies a sort of level of cognitive ability, of sophistication, of viewing the world that I think is very familiar to us as sort of homo sapiens as modern humans, and it tends to make them more like us. Because they had other cultural ways that we know about, not just as painters. That's right. I mean, like living people, different groups of Neanderthals did different kinds of things. So some of them seem to have buried their dead.

For example, some of them seem to have cared for the old or the infirm people who needed to be sort of supplied by the rest of the group. Things that, again, we sort of link as sort of very human-like behaviors. And so this is part of a bigger picture. It's nice that let us move away from older studies that really focus on what they ate or what such of tools they made. And there's really sort of more, I think, sort of socially interesting kinds of things about who they were. Let's talk about the art a bit. Why is art so connected to this idea of symbolic thinking?

And why is symbolic thinking an important trait? That's a really good question. We seem that we're humans. We always think that we're special. So we think this is something that we do in that other groups, for example, people look for other living primates like chimps, gorillas, these things, symbolic or sort of abstract thinking is often believed to be something sort of unique to us. And so when you think about some of our closest ancestors,

which the Nautilals are, that they're extinct, it becomes a big question, how like us were they? And so the ability to sort of think abstractly with symbols is a big part of that question. And again, I think the root is really how much like us were they? And the reason this is important is we're here and they're not, right? And it's one thing to think about, okay, they went extinct, we're still here, maybe we were better adapted in that scene of the story. But it's quite a different story if you start to think, well, they had art.

They buried their dead. They buried, you know, they sort of thought abstractly. And then our sort of role in their extinction becomes, I think, sort of more profound question. Chris, would you agree? Yeah, absolutely. And this evidence of cave art is just adding further. to the other evidence for, sort of symbolic in ornamental use. There's other evidence that they are using perforated shells, shells stained with pigment,

bird feathers and even eagle talons. So this is all presumably as personal adornment. So this is sort of comparable to what we see from modern humans at a similar time. So yeah, absolutely. It looks like there's a building level of evidence to suggest they do have, a slightly higher level of symbolic thinking than we previously thought. No one is saying that this pigment on the cave wall is sort of an accidental splash or anything is to genuinely put on there as a piece of artwork.

Yeah, I mean, we've got this range of motif. So the most convincing from this perspective is the hand stencil. So this is from Capeo Maritrazzo in central Spain. now this is quite a narrow, narrow shallow, not shallow, narrow cave that's got about 60 hand stencils in it and it would require them to prepare a light source, enter the cave with some pigment prepared, and then they've actually got to hold their hand up

and then spray this pigment over the hand, probably out of their mouths, in order to create this stencil. So that's certainly not something that's accidental. This is Science Friday from PRI Public Radio International. I can imagine the people who stumbled upon a stencil of a hand on a wall must have been aghast at seeing that in a cave and certainly thinking it was 60,000 years old. Yeah, I mean, these are quite common motifs the world over.

In fact, they're found in places like South America, Australia, Indonesia, Egypt, So there's something quite fundamental about them in that different human groups were creating them. And interestingly, they often seem to part some of the earliest phases on different sort of multi-phase sites. So if you've got multiple different layers, they're often at the base. So it's almost as if there is some kind of marking of territory situation going on. Although what they really mean, of course, we've really really really. just don't know. It's interesting. And Christian, how does the art from these Spanish caves compared to what we're finding from humans in Africa during the same period? That's a really

good question. I mean, because that is one of the better comparisons you can make, right? You've sort of got, for, as far as we can tell, for large expanses of the last ice age, you had Neanderthals in Europe, Western Europe in particular, and you had modern humans, almost apians in Africa. So you can sort of compare different continents at the same time. In Africa, part of its geology. The geology is a little less forgiving, and that the caves that would kind of preserve ancient paintings aren't as common or may not exist at all. So there's not as good evidence for a cave painting in Africa, and the funding's a little bit less. So the evidence may be out there, but we don't have really good, very well-dated ancient African cave paintings.

There are things, I think, Pierce Shells were mentioned. So you do see on sites on either into the African continent. In the Mediterranean and on South Africa, you see people using seashells and piercing the seashells, putting a hole in them, or sometimes collecting ones they found on the beach that have a hole on them, but clearly sort of wearing them in some way, either as sort of jewelry or sewing them on to things. In the middle of the continent, where you don't have seashells, you have people using ostrich eggshell beads. By about 40,000 years ago, and even a little bit older, people are breaking up a big ostrichageageagee shell into little fragments and carefully grinding these beads down, piercing them in holes,

and putting them on strands. So you have a sort of a different tradition, but still modifying things for personal ornamentation by 45,000 years ago. So part of it is a different record just on what preserve, right? I mean, we're lucky to have anything the last 45, 60,000 years ago. Well, is interesting, any of these discoveries or anything new that we're talking about in the world? of Nandatals give us any idea, get us closer to why they died out and we didn't?

Is this for me? Well, go ahead. Take a step, Christian. I don't know. I mean, for me, this is the million-dollar question, right? As an archaeologist, of course, I want it to be something about behavior or things. This is what we study. That may be, or it may be things about biology, right?

It might be things about disease resistance or frequency of, birth or the ability of, you know, sort of child death rates, things like this. Or it might be that modern people have sort of figured out solutions to sort of of live in dense groups of people that weren't related to them. They figured out a way to sort of communicate with groups across space. We have

some hints of this in the record about if you look at the way, it's a funny thing that archaeologists look at. They look at how far rocks people are transporting across the landscape and the stone tools they have. If you look at Neanderthals, they don't seem to move these things very far on average. If you look at modern humans at the same time, on average,

moving these things over greater distances, and it implies sort of these bigger social networks. They know people, not just the next valley, but they know people two, three valleys over. And that's useful in a situation where if you've got a bad time, a bad year, you might know a big network of people you can tap into. You know, look, Joe, we helped you about two years ago. Can you help us out now? And it may be that Neanderthals didn't have that sort of big a social network to fall back. Now, science loves a mystery, and this will continue. I want to thank you both of you for taking time to be with us today.

Chris Standish archaeologist at the University of Southampton and UK, Christian Tryan, Associate Professor at the Department of Anthropology at Harvard University. Thank you all for taking time to be with us today. Thank you very much. You're welcome. Have a great weekend. PJ Leiderman composed our theme, and if you missed any part of the program, I'd like to hear it again. We always have our podcast, and if you have a smart speaker, you can ask it to play Science Friday whenever you want.

Every day now is Science Friday. The podcast will come right up on that, too, and also say, say hi to us on Facebook and Twitter and Instagram. You can also email us, SciFri at ScienceFriaddy.com. We'd like feedback. Tell us what you'd like us to cover that, you know, it's going to float your both. Speaking of which, have a great weekend. We'll see you next week.

I'm Ira Flato in New York.