Mini human brain grows blood vessels; The geoengineering risk of termination shock; Trove of ancient fossils discovered

0:00We're leaving today and entering a world of Mickey Mouse waving, Princess meeting and greeting. Lightsaber clashing. The Twilight Zone Tower of Terror dropping. Banshee flying. Space Mountain launching. Galaxy rewinding. What's the whole deck with galaxy rewinding? Fireworks igniting. World of Other Worlds. For whatever you love. Infinite worlds await at the most magical place on Earth. Walt Disney World Resort. Mini human brains grown on a dish in a lab. Now, are you ready for this? We have mini human brains growing with blood vessels connected to the neural tissue. With blood vessels. If it's getting too close to our brains, then of course it brings up ethical questions about what experiments we might do.

0:48Also this week, new research on solar geoengineering suggests it could actually be even more costly than unabated global warming. Geoengineering is a band-aid. It's masking the symptoms, it's not treating the disease. And we'll be hearing why that is. We also have a report on an incredible trove of fossils half a billion years old, showing what life on Earth was like just after the first mass extinction event. They've analysed more than 8 ,000 fossils so far. The majority of them are arthropods. They include things like trilobites. I had to run away and get my trilobite. I did have some brachiopods somewhere but I can't find them right now.

1:24Yeah, I've got some upstairs.

1:31Welcome to the world, the universe and us from New Scientist. I'm Dr. Penny Sarche. And I'm Dr. Rowan Hooper. Today we're talking about growing a human brain in the lab. And it's one of those stories that if you were going to tell someone about this like 20 years ago, it would just sound incredible, wouldn't it? Like something out of a pulp science fiction novel. I don't know if you remember when you first interviewed me for a job and you said what's your dream story that you'd break on the news desk I said a brain that works in a box. It's still my dream story. I don't remember that because that's always the secret question we ask isn't it what's your dream story?

2:07I know we've ruined all future recruitment now. But look we're not there now like we haven't got a whole human brain in a box but we're getting there and that's what we're going to talk about today. Yes, and this comes down to a kind of technology that's used for all kinds of organs, growing organoids in the lab. And it basically involves taking stem cells and coaxing them in a dish or a container to develop into a small form of an organ, maybe a liver, a kidney, and sometimes a brain. Yeah, so I said 20 years ago, but the brain organoids were first created in 2013. and they resemble a fetal brain or a newborn brain in terms of organisation.

2:49And they're being used to investigate things like autism, schizophrenia, dementia, conditions like that. And one big hope for them is that they might be able to help tell us what makes human brains unique. We'll get on to that in a minute. But brain organoids so far, they've always been these very small blobs, a few millimetres across. So you can call them mini brains, but they don't really look like them. That's good in some respect, because we hope that means that they don't feel anything. They're not conscious. But it also means that they don't last very long and it limits what we can do with them.

3:24And Carissa Wong is here to tell us what's now changed. Carissa. Yeah. So as you mentioned, these brain organoids, they're these tiny like cream colored balls. And if you compare that to like our actual brains or the developing brain, you'll see this beautiful network of like red blood vessels that are supplying the whole brain with nutrients and oxygen. And so the next step here is that researchers have managed to grow blood vessels around these mini brain organoids that seem to resemble what you would find in like a developing brain much more closely than prior attempts. So blood vessels are key in this, aren't they?

4:02because if we want to have things that are more than just a lump of cells, barely visible, you need that blood supply to allow it to grow bigger and have more complex organisation. So what's the step here? Are they getting towards that? Yeah, exactly. So the step here with the blood vessels they've made is they have a really clear lumen or hollow structure that haven't really been shown to be produced before in these brain organoids with blood vessels. So the researchers did this by essentially growing stem cells, as you said before, in this lovely nutrient fluid that got them to develop in a way that formed something similar to the developing cortex in the brain.

4:44And this region is kind of involved in things like memory, thinking, and problem solving. And the researchers at the same time grew organoids that were made of stem cells which developed into blood vessels. And the key thing they did here then is to attach one blood vessel organoid to each end of their cortical organoids, the ones that are like the developing cortex. Okay, so the blood vessels started growing into the nervous tissue. And so you do get this kind of what begins to be a mini brain with blood vessels. And I don't know, is that creepy? Especially when you mentioned that it's the cortex, that's the really special bit where, as you say, we think and we have memories, we have feelings.

5:32So we're starting to really wire up that part of the brain in this tiny brain on a dish. Yeah. And what they found with this sort of blood vessels that were around this brain, they had genetic activity that was much more similar to what you would see. in the developing cortex and they had physical properties as well that were more similar. So yeah, as you say, potentially you might find that a bit creepy, but I would say that we're far away from being anywhere close to an actual developing brain or anywhere close to like an adult brain as well, which you might be sort of thinking about there. But presumably more sophisticated brains in addition is actually the goal of this research.

6:16Yeah. So the idea is to make these brain organoids more close to what we will actually have in ourselves. But of course, you've got to be careful about potentially, people have said about how far you take that, because if it's getting too close to our brains, then of course it brings up ethical questions about what experiments we might do on these organoids. Yeah. Okay. So the whole point of this is, as you say, to keep them alive for longer by getting oxygen to them, getting nutrients, doing what blood does to them. But okay, we've got the blood vessels, but how would you then get the blood? How do you pump blood to these tiny little things?

6:58Or can you just infuse it? Do you need an artificial heart now to start pumping through? Yeah, so that's a really important point. So although we're showing in this study that we can achieve blood vessels that look much more like actual blood vessels in these organoids. As the inventor of brain organoids told me, Madeline Lancaster, she said, well, to really get these to behave like blood vessels, we would need to connect the network of blood vessels to some outside system that pumps in a blood-like fluid or blood itself through these organoids. And actually, it's really difficult to interface such fragile vessels with something artificial that maybe we're pumping into it.

7:39Okay. So she thinks that means that we're a very long way from having a more functional living tiny brain. Although they are doing amazing things, isn't they? We reported on one of these mini brainoids a few years ago where they'd grown optic cups on the brain. So this was basically the early stage of an eye. And it had a lens, a retina, cornea, and then neurons going like a primitive optic nerve into the rest of the brain tissue on the dish. So they're doing pretty sophisticated stuff. They managed to give these things eyes. Yeah. And that's actually an important point when we consider how close these are to being brains, maybe even like ours, that can have conscious.

8:29sort of ability because basically in order for the brain to become conscious some people say it needs to be able to sense things from its environment and process that and think about it because if you've got nothing to think about are you really able to think and be conscious wow that's a that is a deep question so is is that what when you mentioned the safeguards and ethical considerations that people are thinking about is that the sort of thing they're thinking about like whether it consents or not is a factor about whether it will then be able to think. Yeah, so this is like under a lot of discussion among researchers in the organoid field and there are these ethical boards that sort of set out some ideas about how we ensure we don't start experimenting on these little organoids if they have a conscious brain.

9:24But yeah, as I said, we're really far from that and um while yeah having the ability to sense is one of the thresholds with which we might argue that they need to be conscious but um this is still something that we need to tease out and there's a lot of discussion and debate about what consciousness actually is as well what about when it comes to asking questions about our i mean our brain loves to tell us that we have a unique kind of brain that it's unlike anyone else as any other animals Can these little blobs in a dish tell us anything about what, if anything, is super special about our brain?

9:59So there have been some studies showing that if you grow like chimpanzee brain cells in a dish or mouse cells in a dish, they look more similar to each other and our human brain cells seem to form quite a slightly different structure and behaviour. Yeah, I think you're talking about a study last year that showed if you grow human stem cells in a mini brain, our ones develop more slowly and the stem cells have a longer time to expand and generate more stem cells which lead on to more neurons so maybe there's already from an early stage a difference in in this slower but more complex growth that you get in in human brain oids than you do from a mouse or or from even from a chimp but say numbers of neurons isn't the whole story right Otherwise, whales would be the smartest things alive.

10:49Yeah. Yeah. I mean, some whale brains are the size of a bloody car, aren't they? I mean, yeah. So it's the connections between them. And we know that our brain has, the human brain does have these huge numbers of connections to other neurons. And that's part of the secret sauce, probably. But then about the problem of keeping them alive, there's this other thing, which to talk about the creep factor a little bit more here, is that some groups take these brain organoids and then implant them into a mouse brain to keep them alive in there and to keep them ticking over, literally feeding them. And then you mentioned the problem of consciousness.

11:31We asked this last year to a researcher who said, I think this was Madeleine Lancaster actually, and she said that they're not worried because as you say, if the brain has never experienced anything, it just has no sensory input, then it has nothing to think about. It's too small. It's got no body. There is no way, she argues, that it could ever sense or interpret anything and therefore think or feel. Are you convinced by that? It's so hard, isn't it? It would be almost like a suspended animation, like a lump of neural tissue in sleep mode. It's not really sensing or thinking anything. Yeah, exactly.

12:12It's had no input at all. And I think this is another thing that people talk about when they talk about uploading the brain. If you were able to do that, the brain might exist, all its connectome might exist digitally. But if it has no input, it has no body, then it may not have consciousness as we know of it. But yeah, This is all very far away. But what's amazing about this research is it brings these questions into reality, into something that's not out of pulp science fiction.

13:07good. Seeing these people pay for what they'd done felt righteous. True Spies from Spyscape Studios, wherever you get your podcasts.

13:20As global temperatures continue to rise and as efforts to cut greenhouse gas emissions don't proceed fast enough, the prospect of catastrophic impacts of global heating are getting ever more real. So for that reason, we're hearing more and more about interventions to artificially cool the planet. And most often when we talk about this kind of geoengineering, we're talking about solar radiation management, this idea that we could dim the amount of sunlight that reaches Earth. Yeah. We just talked about brains on dishes and this is another huge idea, isn't it? Dimming the sun. But that is the one we know most about, the one most likely to be used.

13:59But obviously there are a huge number of risks in doing something like that. And one of them is that if you do start dimming the sun, you can't stop. You're committed to it for a long time, and it's a huge effort. And sometimes when we're talking about this, thinking about this, I think, well, okay, fine. It's a big effort. So let's not stop doing it. But that is easier said than done. And a new report now shows just how dangerous it could be if you start and stop, if you start this solar geoengineering, and then you stop it. Alec Loon, you've been reporting this. Alec, should we start first with a recap of where we're heading?

14:39Yeah, so right now we're on a trajectory for 2.7 degrees Celsius of warming by 2100 if we meet all of our climate goals and commitments that governments have adopted. Now, what this study did was it looked at a higher risk scenario. It said, what if we don't meet those climate goals and we just keep on emitting more and more fossil fuels as we are currently doing? You know, what would happen then? Because that would be the situation where we might, you know, be more seriously looking at geoengineering this really high risk, high fossil fuel scenario in 2100. And so in that scenario, you could see temperatures reach something like 4.5 degrees Celsius above pre-industrial by 2100.

15:26And that would cause huge economic damages. This research calculated those, estimated those damages at at least$868 billion by the end of the century. Which actually doesn't sound very much to me. Like 4.5 degrees causing only that much damage? I don't think so. They were saying that these numbers, they were deliberately using the most conservative estimates they could possibly use for these numbers so that people wouldn't accuse them of kind of, you know, being out to get, you know, out to kind of undermine geoengineering because it is such a heated topic, right? So they were doing risk-risk analysis.

16:07They were using conservative numbers. And they said that if there was a hypothetical stratospheric aerosol injection program that was injecting aerosols high into the atmosphere beginning already now, that could maybe keep temperature rise to about 2.8 degrees Celsius. So, you know, shave off, what is that, you know, at least 1.7, 1.8 degrees. And that could more than have the damages to$393 billion. So tell us then, what would that entail? What would it really mean to mount a sort of global solar geoengineering effort? So this is why these guys are looking at this, because it would be a huge effort.

16:53You would have to, you know, there was a study done a year or two ago that kind of gamed out this whole thing. And they said that to cool the Earth by one degrees Celsius, you would need at least 100 aircraft, airliners, big aircraft spreading many millions of tons of sulfur dioxide in the stratosphere every year. They would have to be flying near to the poles because that's where the stratosphere is lower and the commercial aircraft we already have can actually reach the stratosphere. Otherwise, you'd need completely new aircraft that can fly even higher with large payloads. And they have to do that for hundreds of years without interruption because the second you stop doing it, the temperature starts to rebound and it starts to rebound much faster.

17:41And that's where you get real problems. Right. So 100 years of 100 aircraft flying around, it could potentially halve the economic cost globally of climate change. But there's this big problem of what's known as termination shock. What happens if and when we stop doing it? Yeah. So if we stop doing it, then all that warming that we have been masking with the geoengineering comes roaring back. People have described it as being like opening a globe-sized oven door, right? And you just get that blast of heat. And so that can be really damaging because climate change now, it's happening, but it's happening very gradually or relatively gradually.

18:25Whereas termination shock, you could have all that climate change happening in just a few years. And so that wouldn't give humans time to adapt. It wouldn't give ecosystems time to adapt. And so this research found that if this hypothetical geoengineering program was suddenly terminated in 2030 and temperatures rebounded by 0.6 degrees Celsius over the next eight years, then the damages would be more than$1 trillion by the end of the century. So it would be even more costlier than just doing nothing and letting this high emissions scenario, this very large amount of climate change just happen.

19:08Okay, so two terrible things to consider. But with this termination shock, the unmasking, we've reported on this recently, haven't we? Because we have seen that kind of natural event of unmasking as a result of some emissions clear up, shipping emissions regulations that has led to this unmasking, hasn't it? Yeah. So a lot of times scientists like to talk about how we've actually been doing a kind of geoengineering experiment through widespread pollution, and shipping was a big one. And so when in 2020, the IMO banned or cut down on sulfur emissions in shipping, then that led to additional warming.

19:50That's one of the reasons why global warming has sped up in recent years. So scientists say that, you know, there are different estimates, but somewhere around half a degree Celsius of warming was unmasked by that by that crackdown on sulfur pollution. And, you know, that, that, you know, right now that's costing us billions of dollars each year. That's causing us to near or cross tipping points in the climate system. So warm water coral reefs are already past a tipping point, scientists believe, and we're nearing ones on the ice sheets in Greenland and West Antarctica. And this is really important too, because, you know, when ecosystems don't have time to adapt to, let's say termination shock, a sudden rebounding of temperatures, then that means that there's more risk of tipping points being crossed, right?

20:40Because if ecosystems are collapsing and not kind of cushioning us against this, then tipping points can be crossed sooner. And so that's another part of the damages that could come from termination shock. So overall, this is telling us that we already know geoengineering was really risky because there are things like it could change the monsoons, it could change rainfall in different places, have these knock-on effects. But what it's telling us now is that this risk of termination shock should not be underestimated at all. And maybe that means that overall, the risk of geoengineering, solar geoengineering, is even worse than we thought.

21:20Yeah. And this research, I think, brought two things to this debate. One, it put some actual numbers on this, And it calculated those numbers with not just the amount of warming that we might have at a certain point, but the rate at which that warming would occur. Because as we've been saying, the rate is really important. If it comes back really fast, it's much more damaging. And so they've incorporated that into the damage function. They've made these estimates of the economic damages. And then the second thing they did was they went further and they did some modeling of what are called decision surfaces, where they basically have the risk of the probability of failure, the probability of termination shock on one axis.

22:00Then they have the amount of time over which that termination shock occurs. And then on a third axis, they have the damages. And so this allows you to kind of visualize in what situations the risks would outweigh the benefits with geoengineering. And what they found was really interesting because for the benefits to outweigh the risks with geoengineering, you need to basically have three things. You need to have the global governance and the international cooperation around this geoengineering program to allow it, if we are going to stop it, to be stopped over a number of years, to taper it off rather than suddenly stop it.

22:37So you can kind of cushion the termination shock by tapering it off. Second thing is they said we would need to have the global governance to basically do enough emissions mitigation to reduce emissions enough that it wouldn't be a huge rebound in temperatures. And then the third thing is we would need to keep the probability of failure in any given year very, very low. Because if you think about it, let's say there's a 10 % probability of failure any given year with this geoengineering program. If you multiply that over the course of 100 years, that's over 99 % chance of failure at some point in that 100 years, right?

23:16So you have to have really tiny fractions of a percent chance of failure for this to make sense. And this is where what the researchers call the governance paradox comes into play. Because basically, if you have so much international cooperation and governance of this geoengineering program, that you're reducing temperatures or you're reducing emissions to limit the risk of termination shock, then why don't you just reduce emissions? Why do we need the geoengineering at all? The whole point about geoengineering, the whole reason we're talking about it is because governments are not doing enough.

23:50There is no good governance on climate in the world right now. Yeah. I want to come back to that point. But before then, let's talk about the problem of regulation at the moment because people are just going ahead and doing this stuff anyway, right? On a very small scale, you get these startups that are out there testing out different strategies because they have dollar signs in their eyes, don't they? They can see some money to be made from this. Yeah, the most famous is this Silicon Valley startup called Make Sunsets. And they've released more than 200 balloons of sulfur dioxide into the atmosphere.

24:25These are basically just weather balloons filled with sulfur dioxide. And they got in a lot of trouble in Mexico. They reduced where this research was done, actually. It's done by Mexican researchers. And in that country, Make Sunsets released these balloons. And the government found out about it and threatened to ban geoengineering. entirely because these guys were just kind of vigilante geoengineers out there doing it on their own. So that's one thing. But I think something that has caused people to take this far more seriously now is that over the past year or two, an Israeli company called Stardust has raised$75 million for its own solar geoengineering technology.

25:07And it was lobbying the US government undeclared lobbying that was exposed by journalists about its solar geoengineering. So in other words, this is getting very real very fast. And the new scientist did a cool survey last year that found that two thirds of scientists expect there to be some sort of solar radiation management, solar radiation modification tried this century. I found that really scary. And it does sort of suggest that we need to think governance sooner rather than later. But I wonder about people, unlike myself, who are tech solutionists. And is there an argument to be made that we could be doing this whilst also getting really good at sucking carbon out of the atmosphere and spurring it away?

25:54And then by the time we stopped doing something like this, we could have totally fixed our problem. Yeah, that's one of the main arguments for geoengineering. It's often described as shaving the peak. So geoengineering is just shaving the peak in temperatures. It's kind of softening the blow of global warming until we can get grips on it, right? And do lots of carbon removal, reduce our emissions, right? But yeah, it's just the risk of termination shock, you know, it has been kind of underestimated, I think, this study is showing us. And well, this research makes a strong case to do more research into geoengineering, which is something that not all scientists agree on.

26:36Some scientists have been calling for a moratorium on geoengineering research based on the argument that it will make it more likely that we will do geoengineering if we've been researching it a lot. And I think this study, I was talking to some scientists who said this study is an argument against that because it was done as part of a geoengineering research initiative that funds geoengineering research in countries in the global south because those are the countries that are experiencing the most impacts of climate change. They're the ones most vulnerable to those impacts, and they would be the ones that could stand to gain the most from geoengineering.