Scientists test engineered microbes to fight disease; Has 1.5 degrees failed?; New theory why we’ve not found aliens

0:00Hello and welcome to The World, The Universe and Us, the weekly news podcast from New Scientist. I'm Dr Penny Sarche. And I'm Dr Rowan Hooper. On today's show we discuss the controversial proposal that we abandon the 1.5 degrees target as the limit for global warming and instead set it at 1.7 degrees. We're also going to hear about the earliest evidence for plate tectonics on Earth and find out how that influences the outcome of the Drake equation and that's the number of extraterrestrial civilizations in the Milky Way. So that's the world and the universe and us. Yeah, where's the us in our title?

0:35Well, this week we've got exciting news of how we could modify our microbiomes. The gut microbiome has been implicated in everything from cancer to mental health. And as we've begun to understand this more deeply, there's been this kind of tantalising question of can we use science to smartly improve and fine tune our microbiota in a way to sort of prevent or even treat these diseases. So this week, there's news from a small trial that gave people genetically engineered microbes in an attempt to prevent kidney stones from forming. Niche. Yeah. Well, not actually. Kidney stones affect one in 10 people, apparently.

1:11So quite common. Could this be the first step, though, is the big question towards gene editing our microbiome and treating all kinds of things. And Grace Wade is here to tell us more. Hi. So what's really interesting about this study is that usually when researchers have tried to change people's gut microbiota, they either focus on giving them naturally occurring gut bacteria or genetically modified bacteria. But this usually doesn't work because these newly introduced bacteria struggle to move into the gut ecosystem and successfully establish themselves there. So Weston Whitaker at Stanford University and his colleagues have genetically modified a bacterium that is already abundant in most people's guts called Phocicola vulgatus.

1:54And he told me they chose this one because they know it's already good at colonizing the gut. Right. So what genetic changes then did they make to this bacterium? Well, they wanted to reduce the formation of kidney stones. So they made three genetic changes that together enabled the bacterium to break down oxalates. These are dietary compounds that contribute to kidney stones. And they also boosted these bacteria's chances of survival over and above the bacteria already living in the gut. When they gave rats these bacteria and fed them a high oxalate diet, they found that the bacteria reduced the levels of oxalates in these rats' urine by about half compared with controls.

2:33Okay, and have they given it to people? Yeah, so they did. They gave it to nine people who have this condition called enteric hyperoxyluria, which makes the body absorb too much oxalate. And so what ends up happening is people with this condition keep getting kidney stones. And it sounds awful. And over the 28-day trial, the researchers found the bacteria brought down oxalate levels by about 25%. And, you know, while that sounds small, other trials suggest just a 20 % reduction would be enough to reduce the symptoms of this condition. So as we mentioned, kidney stones are actually quite common.

3:10And if you get one, there is a decent chance that you'll get another one. So it's this kind of recurrent thing. So I can see how this is cool for that. But I guess what we're really interested in here is, is this the first step to taking this much more widely and engineering bacteria to treat lots of other conditions? Absolutely. You know, one expert I spoke with described this approach as a real breakthrough because it shows that it actually is possible to get engineered gut microbes to colonize the gut and also to have a therapeutic effect. And these are things that we've so far been struggling to do.

3:43So if we can finesse this approach, there are so many conditions that the microbiome has been linked to. Alzheimer's, diabetes, chronic fatigue syndrome, and it potentially opens up a whole new approach for targeting these. Yeah, targeting those, but also mood, desire, and many different cognitive things. It's really exciting, this. I went to this lab at Imperial College. They're making these synthetic, symbiotic living materials that you would potentially one day use as an implant in the body. So at the moment they're thinking of them just as sort of external patches on wounds, but it produces hormones and enzymes that the body might need and they might speed up wound healing.

4:27So they've made these things called sin scobies. A scoby, if you made kombucha or vinegar, scoby is the mother of vinegar or the mother of kombucha. So that's like your starting culture. And so scoby stands for symbiotic culture of bacteria and yeast. and what making a synthetic one means that you get those two organisms that produce the material and then you gene edit them to make the thing you want. So you can make the yeast produce whatever enzyme or nutrient you want. You make this material and then you can either put it on the wound and it helps that or in the future maybe ingest it and it will produce any hormones or enzymes that you want or need.

5:10Gosh, that's quite mind-blowing. It's really cool. One of the clever things they did in this study, Grace, was that they engineered these bacteria to be able to digest a seaweed carbohydrate. And the idea was that you then eat the seaweed and it gives the engineered bacteria a competitive advantage and it helps them establish in your gut. And then when you're done being treated, you could just stop eating the seaweed and the bacteria sort of fade away, which is quite a clever mechanism. Yeah, it's a really innovative and elegant solution to this problem they've been having of finding a way for, you know, the engineered microbes to colonize the gut.

5:44So how did it pan out? Did it work well? Well, some of the participants did have mild gastrointestinal problems, you know, which you might expect when tinkering with the gut microbiome. But perhaps a bigger issue is the genetic sequencing of the gut microbiome showed that special genes that enabled the bacteria to feed off this carbohydrate had spread you know they actually swapped their genetic material with other bacteria in the gut they must have half expected that because that that's what bacteria do isn't it they're just always uh horizontally swapping swapping genes around it's not really something you want happening in your body though if you're trying to like fine tune these genetically engineered bacteria inside you yeah you need a kill switch somehow don't you to stop that.

6:28Yeah, that's certainly something they want to iron out in future studies. The good news is, you know, the genes they gave these bacteria, they don't believe will cause any, you know, harm or are concerning at all in the participants. Super interesting. Looking forward to seeing what happens with this in the future. Thanks, Grace. Thank you. You're listening to The World, The Universe and Us, the weekly news podcast from New Scientists. Still to come, a resolution to the Fermi paradox, really, about why we've not discovered alien life yet. Looking forward to that. Now, we heard from scientists last month that we've got just three years left at the current rate of carbon emissions before we breach that 1.5 degree C of warming.

7:13And that's the crucial threshold temperature that nations promised to limit warming to under the Paris Agreement. Now, what happens when we go past 1.5? Well, we're already seeing it, really, aren't we? We're seeing dying corals, rising seas, floods and heat waves right now all over the world. But what will it mean for the future ambitions to get a handle on global warming and climate change? What do we aim for if we fail 1.5? And here to tell us more is news scientist, environment reporter Madeleine Cuff. Hi, Maddy. Hello. So yes, Rowan, you're right. Under the Paris Agreement, nations have promised to keep warming.

7:56Well, they've promised to hold warming well below two degrees and to pursue efforts to limit the warming to 1.5. So now that we've got 1.5 looking pretty shaky, given how much we've omitted since the Paris Agreement was signed in 2015, attention is now turning to what this phrase well below two degrees really means in practice yeah i mean it's so so ipcc language isn't it well below and pursue efforts to that that way of talking and you know why they do it diplomatically but when you have to actually then work with it what does it mean well was was the idea originally was that it would be a ratchet and we'd start off and then we'd we'd all gradually get more ambitious and it might get locked in and that just hasn't happened.

8:43Well that was the idea behind the Paris Agreement structure more generally was that countries would progressively set more ambitious goals to get to those headline targets but to be honest the well below two degrees formulation I think was just what everybody would agree to in the room to get the deal over the line and don't forget that these UN agreements have to have unanimous agreement from every country on earth in order to get signed. So even to get I'll lobby for putting that phrasing in. Even to get anything over the line is pretty impressive under those circumstances. But yes, you're right.

9:16It does leave quite a lot of ambiguity over what that kind of target means in practice. Yeah. Yeah. I mean, if we say 1.7, we'll agree that is well below. But 1.8 is not well below two, is it? So are we going to become slippery slope to being actually at two? Yeah, and the fear is, I think, that people will look at the article of the Paris Agreement where these goals are set out and see the numbers 1.5 and see the numbers 2 and think, OK, well, if we haven't met 1.5, we'll need to meet 2 and therefore look at all the pathways for two degrees of warming. But the problem is if we aim for two degrees, we might well exceed it because we've got lots of uncertainties in how the climate system is going to respond to these rising temperatures.

10:04So there are plenty of model pathways that will aim for less than two degrees of warming, but they will have, say, a one third chance of overshooting that level because we simply just don't know how certain elements of the climate system respond as temperatures get higher. So we can't say let's go for two degrees without there being a strong risk that we will actually end up with much more warming than that. And if we do just sort of abandon 1.5 and opt for two as the next one, that's kind of counter to the whole spirit of the Paris Agreement, right? Yes, exactly. So one climate scientist described this to me as saying, if I told a child to stay well away from a cliff, I wouldn't mean go right up to the cliff edge and no further.

10:46So it's all about trying to figure out what the level of risk and appetite was in that kind of original phrase. So this is a really live area of discussion among researchers now as this 1.5 degree threshold looms. And they're really trying to figure out what the peak temperature is that we can safely get to while staying within a, quote, well below two degrees limit. So one team at Imperial College London recently presented their findings and they concluded that to give a decent chance of remaining below two degrees of warming. So in their eyes, that meant an 83 % probability that we would remain below two degrees of warming.

11:27That means keeping any temperature rise to an absolute peak of about 1.63 degrees. I'm just thinking of this metaphor of walking along a child walking along a cliff edge but you could kick the child off as long as they're on a rope and then drag them back off that's what we're effectively arguing for with carbon storage and removal right well I think that's yeah that's what we're essentially is going to happen with the 1.5 so we're throwing the kid right we're throwing our own child off the edge of the cliff but it's all right they're on a bungee cord I'm worried we've got two cliffs set up now a 1.5 degree cliff and a two degree cliff okay what what's the benefit of coming up with another kind of number yeah i should also say that it's not just these researchers at imperial that have come up with this figure there's another team of researchers in austria who recently floated 1.7 as a good measure for what well below two degrees means and and these researchers say that this it helps to clarify the roadmap for decarbonization so there's no room for this weakening of targets like we've discussed the suddenly shooting for two degrees not 1.5 degrees for example it kind of makes clear what the minimum level of action is needed to fulfill the commitments made at Paris.

12:43One researcher described it to me as like a policy guardrail to stop any backsliding so 1.5 degrees will always remain the ambition but you know around 1.7 would be the upper limit of what is allowed within that framework. It does still feel like they're moving the goalposts though doesn't it? But we have to because we're shooting past 1.5. Because we're not doing anything. Yeah. But what do vulnerable countries say about this because they're the ones that really were pushing for 1.5 back in Paris because they are the ones that are at most existential risk from sea level rise. Yeah so for exactly that reason this thread of research about whether or not to clarify a post 1.5 degree goal is proving really controversial.

13:25I had a chat with Alana Saeed. She's the UN ambassador for Palau in New York. And she's also the chair of the Alliance of Small Island States, which is a UN negotiating bloc that is really forceful on climate issues because their countries will not exist above 1.5 degrees of warming. Here's what she had to say. For AOSIS, the number is 1.5. And that's our rallying call. And we don't want to entertain. Yeah, so we don't want to be distracted by that conversation. We know where we need to be. There are important reasons for us to be below or at 1.5, and that's where we're sticking to. I mean, I think once you start opening that discussion, then it makes it feel like you've kind of given up on that.

14:09And for us, it's time spent that's kind of negotiating something that is not really relevant to us. It's 1.5, and that's where we need to head to, and that's where we're focused. And anything else is just a distraction. Alana's not alone in feeling like this. There are plenty of other activists and negotiators that I also spoke to that worry that letting go of this 1.5 degree goal or refocusing ambition will signal to governments and markets that failure is acceptable and that it will kind of confuse the public message over climate action. So they would prefer, or some of them would prefer, the focus to remain on 1.5 degrees as the central target.

14:49And any overshoot of that being framed as the planet getting into carbon debt against this goal. I can see the value in that. Is there any way to sort of square this circle between, you know, the value of the 1.5 policy and then what scientists actually believe is now currently possible? yeah it's worth saying that the team working on this concept at imperial weren't framing it as well let's abandon 1.5 and set a new weaker target they say that you can clarify what well below two degrees means without letting go of of 1.5 because in the paris agreement that the goal around 1.5 is to pursue efforts to limit warming to so you can still keep pursuing efforts even if those efforts need to intensify if you've overstretched that goal.

15:42So the idea is it's all kind of coalescing around this idea of overshoot. So they say their threshold of about 1.63 degrees of peak temperatures has this bonus of keeping 1.5 in reach. And like Rowan mentioned, we could use technologies like carbon removal once we've stabilised the global temperature to then bring global temperatures back down below that 1.5 limit in subsequent decades. So we We might find ourselves in a position where there's this globally recognised upper limit of warming of about 1.7, but we absolutely cannot cross. But with the remaining global ambition to eventually get temperatures back down to 1.5 degrees in the long run, and you could see how that framing would satisfy both groups, both the scientists and the activists, perhaps.

16:30What about the policymakers themselves, the people who have to sign up, the countries who signed up to Paris? Is there any indication yet of whether they're going to be on board with that? I mean, they like the well below framing because it does leave a lot of wiggle room, right? I mean, what's going to happen at COP30? Yeah, I have to say it's probably quite unlikely that this becomes a kind of formally adopted temperature threshold at a UN summit like COP30. Because, as we discussed, you need a unanimous agreement to get these things through. the best we can probably hope for is that there's an informal acknowledgement from countries that when we say well below two degrees what we actually mean is somewhere closer to 1.6 or 1.7 degrees and that they draw up their domestic emissions plans accordingly.

17:20We're going to talk about tectonic plates, life on Earth and the Fermi paradox now. The Fermi paradox being the expectation that intelligent life will have evolved many times across the galaxy, but that despite that, we failed to find any aliens. Well, at least we think so, right? Some might be in power around the world. As Enrico Fermi put it, I love this, where is everybody? Yeah, where are they? That's the paradox. Or is it a true paradox? We're going to attempt to resolve it here. We're going to try and answer the question of whether we're alone in the galaxy. But we're going to start with plate tectonics, which of course as you will all know is the system of movement of these vast plates of rock that make up the shell of the planet and they form mountains they their cause the cause of earthquakes and all that stuff so you know it's really embedded in our understanding of the planet isn't it that it's hard to believe that until quite recently it was really controversial and only became accepted in the 1960s yeah i can't believe it was so recent yeah alex wilkins is here to talk about this.

18:26Alex, there's still actually a lot of debate about it, isn't there? Yeah, so as you say, there's a consensus of how it works now. But in terms of when that started, how many plates used to exist on Earth and what that looked like, there really is a lot of disagreement still. So some researchers have found evidence that they could have been existing as long as four billion years ago. That is quite tentative and lots of people disagree with that finding. But more widely, people have found evidence that kind of 3.2 billion years ago, 2.8 billion years ago, it seems to be pretty good evidence. But there's this wide margin of kind of when exactly they started that we just don't have good evidence for.

19:04So last week, I was at the Goldschmidt Geochemistry Conference in Prague. And I saw a talk where the researchers talking were saying that they found evidence of unambiguous tectonic activity 3.5 billion years ago, as well as a reversal of Earth's magnetic pole at the same time. So this is all quite soon after the planet itself formed 4.5 billion years ago and as someone who's very interested in the origins of life lots of bells are ringing here because that period between three billion and four billion years ago there were some really cool things happening on this planet in terms of life kicking up but before we get into that what's the new evidence then for this earlier date for when tectonics may have started yeah so this evidence is actually really different from all the other evidence we have normally geologists look at the chemical makeup of rocks called petrology or looking at kind of the chemical makeup but this is a field called paleomagnetism so they find kind of these preserved magnetization signatures in the rock and if you think about earth's magnetic field as basically a giant bar magnet the anything that is magnetic will line up in the same direction as that bar magnet so the geologists can go back find the magnetization of these signatures that well preserved and find that if they track them over time then they will kind of move along with earth's magnetic field so if the rock is moving if you imagine like a tiny compass and you move it very slowly over time then the needle will slowly move depending on where it is in relation to earth's magnetic field wow so when the pole flips then what happens to the rug so that's another kind of feature the pole is only flipping kind of once every tens of millions of years yeah So presumably they will find a swapping direction of the magnetisation in the rock when the pole flips.

20:47So the rocks in this study then, they're from Pilbara, are they? This is this amazing site in Western Australia. Yeah, so it's actually incredibly rare in terms of kind of geological sites. There aren't many other sites in the world. One other big one that we know of is in South Africa, which is really important for the study that I'll talk about in a bit. But this region is a kind of vast area in Western Australia, about a 12-hour drive from Perth. and the rocks there are really well preserved. So they're in neat layers. You can go down and you can track all the events that happened over this really definitive time region, unlike other areas where it's all kind of crumpled up and difficult to really unpick.

21:24It's amazing that that area survived, isn't it? That's why it's so rare. It's just not been eroded. It's not been subducted. It's still there. Well, yeah, because of plate tectonics. I did an interview years ago with someone who was saying the number of the amount of rocks we have that are around four billion years old is tiny because the vast majority of them have been recycled exactly because of plate tectronics and there's fossils there as well from that that age as well right the earliest fossils a lot of the most exciting potentially earliest signs of microbial cells are coming from pilbar i guess because it's this really geologically stable region yeah yeah no exactly so how are people interpreting this finding then presumably you know it's not like all geologists have jumped on board and we now think it's all tectonics started at that time no definitely not um so there's a really wide range of what people thought tectonics looked out looked like at that time yeah so some people think it was basically an entirely closed lid with no movement at all some people think it was kind of lots and lots and lots of tiny little plates that were all moving about and some people kind of think it was somewhere in between and the difficult thing about this study is that there's still quite large error bars on how much the plates moved so on the lower end you can get people who fit their theory saying there was no movement at all if it's the upper end and it really did move a lot then you'll say have people saying there was loads of tectonic plate activity at that time it's a right old squabble isn't it going for ages um but look we said at the start we're going to get into the how this relates to the origin of life and the fermi paradox because it's more than just this geologist squabble any geologist here i'm not dissing you but you know it is a big deal in geology but it's more than that because without the tectonic plate system we wouldn't be here exactly that that's the argument so tectonic plates are responsible for the kind of constant churning of the earth and when it thrusts rocks up into the atmosphere that's really important for the carbon cycle so rain falling on rocks will either release co2 or lock co2 in the ground and without that weathering then there won't be a stable atmosphere for earth and if there's too much co2 then you get runaway heating and life won't be able to survive so in that way it's really important but also that constant churning of rocks will also release elements and kind of minerals that are crucial for life as well yeah um so that that argument exactly has been made by robert stern of the university of texas at dallas and i spoke to him about about the importance of tectonics to the evolution of complex life.

23:54And here he is. Plate tectonics is a very effective way of increasing the nutrient supply to the oceans, where animal life spent most of its time evolving. You know, life didn't really crawl out of the oceans until about 300 million years ago and then evolved on land. But this nutrient supply It basically allowed the proliferation of increasingly experimental animals and complex. And plate tectonics also does a superb job in regulating the climate of a planet. And there's a number of reasons that that happens, but we've got a superb climate for advanced life. The third thing that plate tectonics does to encourage life is it provides habitats, you know, especially shallow marine habitats, and then on land, different kinds of places, continents where life will evolve, and then brings these habitats back together, and these evolved organisms compete and evolve further in the constantly changing surface environment.

25:11So essentially there's this idea that to have a live planet you need a geologically live planet. Tectonics bring a lot of nutrients into the oceans which gives complex life something to get going on. Tectonics also regulated the climate. It built lots of different habitats to evolve and thrive in. So with that sort of idea in mind then, is this how we're going to solve the Fermi paradox right here right now on the show? So do we expect plate tectonics to be rare and therefore that's why we haven't heard from anybody yet? Some people do. So the Fermi paradox, just to reiterate that, that's that we might expect there to be many rocky planets in habitable zones around their stars.

25:52But according to this resolution of it, if they don't have plate tectonics, then they won't have been able to evolve complex life. They might have got to simple life, but they wouldn't have got much further than that. Yeah, so the kind that could actually come by and visit or send you a message. The kind that could listen to us or send a message, yeah. I spoke to another scientist about this, it's Taras Geyer at ETH Zurich, and he said that small planets also don't have the mass to generate convection internally to have tectonic activity. So Mars is too small, doesn't have plate tectonics, or certainly doesn't now.

26:29and also planetary accretion models suggest that half of the planets that form around stars would also be too small. So that's one thing and the second thing is about the composition of the planet and here he is. Second important factor to consider is planetary composition which in turn depend on the stellar composition. Some stars they're essentially having too much of light elements and resulting planets they have also too much of light elements and as a result you know, crust or oceanic lithosphere that forms is too buoyant and it cannot sink in the same manner as on Earth, you know, cannot drive and plate tectonics and subduction will not be efficient, even in presence of water.

27:12So, and the calculation shows that at least one third of planets would have sufficient, sufficiently heavy composition to support plate tectonics. So then we multiply two probabilities, one half to one third, and we are around 17 % of planets that may potentially support plate tectonics. So by this reckoning, only 17 % of planets have what we need for complex life to occur. Yeah, so that's what him and Stern are saying. So they've added two additional terms to the Drake equation. And that, as you know, is the estimate of the number of extraterrestrial civilizations in the Milky Way that might be detectable by us.

27:52so the two terms are the fraction of habitable exoplanets with significant continents and oceans and the fraction of those that have plate tectonics and if you add those two in it brings the the value produced by the drake equation right down in other words there may be very few um civilizations out there in the galaxy so we're pretty lonely then it makes our own planet just all that more special yeah there's a nice spin on it yeah yeah that's all for this week you've been listening to the world the universe and us do you go ahead and subscribe and spread the word about our show thanks to all our guests thanks to you for listening we'll see you next week bye bye