Fossilised faeces helps explain dinosaurs' rise to dominance
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Welcome back to Nature Podcast. This time, how fossilised faeces can give us clues about dinosaur origins and the search for a fungus that's made mouse guts its home.

I'm Emily Bates. And I'm Nick Pachachow. 66 million years ago, dinosaurs ruled the Earth. This privileged position had been held by these tyrant lizard kings for around a hundred million years, until it was very suddenly cut short. We all know this story, and can imagine a world where dinosaurs rule.

But how did they reach this dominant position in the first place? This is Martin Kvarnström, a paleontologist who's been researching this question.

But now, new research by Martin and his colleagues is shedding light on how dinosaurs went from bit players to the main act in Earth's history, using quite an unusual source of data, fossils known as bromelites.

So bromelites is a term for fossils related to food processing. So it's fossil faeces or coprolites, fossil vomits or regurgitolites, and stomach contents and that sort of thing. Over the years, lots of ideas have been proposed for how dinosaurs became dominant. But evidence has been scarce. The fossil record is pretty patchy, leaving researchers with a lot of question marks.

So these unusual bromelite fossils could offer some vital clues, as they can give insights into what dinosaurs ate and therefore how they interacted with other species, painting a picture of shifting food webs, showing how dinosaurs changed in size and exploited different things for food.

This information could help researchers clear up some of their contrasting theories for how it was that dinosaurs came to rule the roost. And that is because two of the main ideas oppose each other.

In the first of these, chance plays a big factor. One is the opportunistic theory where dinosaurs were basically small critters waiting for their opportunity and as other animals died out they took this opportunity and diversified and occupied all these empty niches. This idea proposes that some random catastrophic event like rapid climate change or a meteor strike wiped out many of the dinosaurs competitors.

thus allowing the dinosaurs to take over. In a similar fashion to how mammals came to be dominant after the non-avian dinosaurs went extinct. And the other one is that they out-competed their rivals, so they were better somehow. They had superior physiologies or better adaptations to certain things and out-competed other animals. For example, many dinosaurs were upright and had more flexible ankles.

so it's been proposed that they may have had superior agility compared to other animals at the time.

So using the fossilized digestive contents, Martin and the team set out to find out which of these theories is more likely. So we wanted to look at what happens in a restricted area because another thing to mention here on the rise of dinosaurs is that it was very complex. So we wanted to look at one area across time and see what happens as dinosaurs are becoming more abundant.

Are there any changes to the food webs? So who ate whom? Are they just occupying old niches of other animals or are they sort of eating some new thing? How are these food webs evolving through time?

To do this, the team collected over 500 bromelites from a place known as the Polish Basin, an area of Central Europe which includes part of what is now Poland. Using the size, composition and abundance of the food fossils, they could figure out which animals they belonged to and how they fed. Something that was quite an undertaking. It took many years.

to put everything together. So we were looking at bromelies from 10 different sites and hundreds of specimens and then we were comparing what we found with bite marks that we find on bones and with a body fossil record to get a good understanding of what it was composed of at these different time intervals and yeah, merging it all together in a comprehensive picture. But that took, yeah, 10 years.

To get a really detailed picture of what was inside the fossilized feces and vomit, they even used a special kind of radiation to get 3D images. So we were using synchrotron imaging, so it's basically a big particle accelerator that we can use to do microtomography, a bit like, you know, with a CT scanner at the hospital, and see particles.

the internal structures in the fossils. So basically we were imaging in three dimensions the food remains or the under-digested food remains and thereby reconstructing diets of these animals. Together the team were able to get detailed insights into what the dinosaurs were eating, sometimes finding incredibly well-preserved specimens inside a fossilized bit of faeces.

In fact, during the 10-year process, they actually discovered a never-before-seen species of beetle. I think that the coolest thing we found were these small beetles. So they're just one, two millimetre long and they're practically complete with antennae and legs and everything. And I think it's absolutely amazing that, you know, over 230 million year old beetles are preserved in 3D with all these tiny structures preserved.

With all this information, the team were able to detail the steps towards dino domination, at least in this particular region of Central Europe. And they were able to assess the two competing theories. But unlike the dinosaurs, it doesn't seem that one of these theories dominates. I think our study shows that it's a more nuanced picture than that.

So it's probably a combination. At first, I think dinosaurs were opportunistic. But at some point, it's an interesting period of time because there's climate change going on. We have more humid environment towards the end of the Jurassic, more plants. And I think towards the end, herbivorous dinosaurs were probably better at exploiting the new resource. So it's actually a combination of these two theories.

Now, more work needs to be done to show that this was the case for the dinosaurs worldwide. Whilst looking at one specific area meant the team could get a very detailed picture of what happened there, it also means that it's unclear whether this was the case for the rest of the planet.

Dinosaurs also first evolved in a southern region of the planet, a long way away from the Polish basin, so it's possible that dinosaurs may have already gone through some changes before reaching the region. And whilst there were major climatic changes occurring planet-wide that may have prompted some of the dino domination, these events haven't specifically been documented in this region.

It's possible that its climate may have been quite different from elsewhere. Martin, though, is keen to look at these other regions to see how well what they found maps onto other places.

And he thinks that bromelites could be a very important resource in future studies determining how the dinosaurs lived. One of the key takeaways is that bromelites are really important for understanding ecology of the past. And they very often contain well-preserved food remains, which I think is astonishing and really interesting. I mean, we found tiny beetles that were pretty much intact in fossil faeces and beetles.

pieces of bones, fish, plants. So I think they're really underestimated but useful fossils. That was Martin Fornstrom from Uppsala University in Sweden. For more on that story, check out the show notes for some links. Coming up, why finding a friendly fungus in mice might help researchers model medical conditions of the gut. Right now though, it's time for the research highlights with Dan Fox.

Bacteria found on a particle of rock retrieved from the asteroid Ryugu have been found to originate from terrestrial contamination. To minimize exposure to Earth's environment, the sample brought to Earth by the Hayabusa2 mission in 2020 was kept in dry and sterile conditions.

Researchers embedded the particle in resin to prepare it for study before imaging the sample and observing 11 microorganisms with cylindrical shapes resembling those of the bacterium Bacillus. That number grew to 147 after three weeks before declining over the next six weeks. A pattern that researchers say suggests the asteroid fragment was probably contaminated during sample preparation.

The authors say that the readiness with which the bacteria colonize the particle, despite precautions, suggests that researchers should be skeptical of future claims of extraterrestrial life in such samples. And that homegrown bacteria can feed on organic asteroid matter suggests that outbound missions also need strict controls to protect extraterrestrial environments from contamination.

If that research has grown on you, you can read more in Meteoritics and Planetary Science. Adult chimpanzees play together to promote cooperation and ease tension, according to field observations.

Previous studies have demonstrated that play among adult chimps can encourage bonding in captivity, but its role has not been systematically quantified in the wild before. Now, researchers have logged 929 play sessions between adults including wrestling, tickling, chasing and mock biting in three groups of chimps in Côte d'Ivoire.

They saw that adult chimps were 75% more likely to play together on days they worked to jointly defend their territory against outsiders and 58% more likely to do so on hunting days. Around 80% of the playful interactions among adults occurred before the group engaged in these risky activities.

The authors suggest that playing could reduce the adult's stress and motivate cooperation. And these findings could help scientists to understand whether wild animals plan ahead. Read that research in full in Current Biology. We often talk on the show about the microorganisms that live in our guts and the important roles they play in keeping us healthy.

But a lot of research in this area has focused on bacteria, and specifically commensal bacteria, those that generally live in harmony with us, and can even help keep the immune system in check. Bacteria aren't the only microorganisms that grow in our guts, though. And this week, there's a paper in Nature looking at another, much less studied group of microbes, fungi.

Although less diverse in terms of species variety and overall numbers, there are a lot of fungi living inside us. But figuring out exactly what they do has been tough. Ideally, researchers would like to study commensal fungi in a model organism like a mouse to get a sense of what might be happening in humans. However, that has been difficult too. Until now.

A team of scientists have shown evidence that a species of fungi first discovered back in the 50s is well adapted to living in the gastrointestinal tract of mice and looks to be a commensal organism. The team hope that studying it will provide new insights into the actions of these fungi on things like the immune system. To find the fungus, the team searched in mice living in different places and on different coasts in the U.S.,

Reporter Benjamin Thompson spoke with one of the paper's authors, Ilyan Ilyev. So first we started with mice that live in more like a wild situation, you know, around farms. But later we realized we live in New York City. So what is a better place for finding mice?

And so we were working with exterminator company, catching mice, collecting material from those mice. And then we decided to also go in an area that is far away. So the mouse populations are separated by a huge amount of land. So they cannot just walk and disseminate something to the next mouse. So what is the biggest other city in the US that is far away? Los Angeles. So we decided to isolate material from mice in Los Angeles.

And the last place where we went is different laboratories. We have colleagues across the country. So we would ask actually for fecal material that will come to us from different laboratories, perform the same assay. Okay, so you've looked in the fecal samples of these different mice then, the town mice, the country mice, the lab mice, for evidence of fecal.

commensal fungus then what did you find so in all that what came out of the mice in new york mice in los angeles mice in the woods and the farms and then mice in some laboratories but not all of them is basically one species and that species is kazakhstania pintulopasi so it's an ease that was discovered in 1952 but nobody investigated what it does and then it

it came back up in 2005 into samples from mice in the National Institutes of Health. And they also described the fungus. So that was very good because when we came across it, then we said, oh, there is a history of it. So that gave us the confidence additionally. And then we basically assembled the genome because now we have the technology to do that. And we had a lot of confidence that

This is the fungus. So this species then, this yeast, Cazextania pintulopezii, that you identified across these different mouse populations, it does seem like it's very good at getting into mice and colonizing their GI tracts. That's correct. So we would colonize mice that don't have the fungus, and the yeast will dominate very quickly their gastrointestinal tract.

it will stay there throughout their lifetime. And then those mice will give birth, and then we find the fungus in their progeny. If you put mouse that doesn't have the fungus with mice that have the fungus, then they get it actually. So it's very, very, very well adapted. And adapted is one thing, but seeing what it's doing, I suppose, is quite a

another. What did your experiment show this fungus is doing once it gets into the guts of mice? Okay, so if you colonize with the fungus, there is no changes in the bacterial populations, which told us that probably doesn't compete. Another important finding here is that we did not find actually any evidence for sharp activation of any immune cell populations or cytokines or other parameters that we looked at.

But we started thinking, OK, if you are a lab mouse, you eat one and the same diet. If you are a wild mouse, you have to change your diet seasonally and daily. You eat what's available. So we started actually playing with that. And once we started changing the diet and we used a diet that is low in fiber, for example, that would lead to change in the thickness of the mucus.

which is produced in the stomach and in the small intestine. You can mimic it also with antibiotics. So the mucus layer basically shrinks. And when that thing happens, the fungus is seen by the epithelial cells and by the immune cells. We found that it activates basically a cytokine called interleukin-33 that is basically produced by the epithelial cells.

And that leads to type of immunity, which is called type 2 immunity. So it seems like there's a double-edged sword to this. Normally then your results suggest that this fungus lives in some sort of harmony in the mouse intestine, except when the intestine is damaged and it sets the immune system off. So it's actually a process that happens with many other commensals. If you think of Kazakhstan, the positive side we found

is that the fungus is switching on type 2 immunity, the evolutionary developed immune arm that protects against parasites. Parasites are very common in mice. So what we found is the fungus protects actually against those worms that can infect the mouse to some extent.

extent. Is that because they kind of compete for a niche for food or for something like that? We don't know. But this one phenomenon that we found, it's a good thing, right? If you think about it. But having an overactive immune system can also be a bad thing, right? Exactly. So because it's in the gastrointestinal tract,

We can induce allergic type of response in a mouse, very similar to foot allergy in humans, and we can colonize the mice or not with the fungus. So what turned out in that experiment is that the fungus actually will make this allergy more severe through switching exactly the same mechanism type to immunity.

then the mice develop very severe allergy. So that's the flip side. Having a commensal can be good and a bad thing depends on your situation. And that's what is actually preserved also for fungal commensals. And so you found then evidence that this is a commensal fungus. Is this just a strange possibility?

thing or could this have broader impact of course mice are used a lot in lab studies and the finding then that this species does seem to have a lot of impact on things like the immune system could that have knock-on effects do you think so yes that can have impact in different ways

If somebody studies type 2 immunity, allergies, gastrointestinal cancer, if they study fungal colonization, if they study anything like that, and they have the fungus and then they don't know about it, that will influence their results in a way that they might even have a misconclusion.

And there are other questions to answer as well, right? One thing that stood out to me in your paper is that you have picked up this species in wild mice and in lab mice, but not in all lab mice. Some of the mice that you could buy from commercial vendors for use in research didn't seem to have this fungus at all, for example.

Yes. So if you buy from certain companies, they don't have it. If you go in certain facilities, they would not have it and others will have it. We haven't sampled at a large scale in the population of mice outside. But if some mice have it or some don't have it, it means that, you know, it's adopted, but it's not in all the population. So that part is something to investigate. I mean...

How does this work translate to humans? What's the link between the two? So the link is that now we have a model organism. And with that model organism, we can study a process of immune activation by fungus. And can we actually translate something from an organism that we have in a lab adapted to a model into human disease or, you know, immunity? The other

questions that we are trying to address is what is basically an analog of this fungus in other organisms and hopefully also in humans because if there is this good adaptation here there could be something else that is very similar and can we do translational studies that way

Ilyan Ilyev from Weill Cornell Medicine in the US there. To read his paper, look out for a link in the show notes. Last up on the show, we're talking about climate change, as the United Nations Climate Change Conference, COP29, came to a close at the end of last week in Azerbaijan.

Flora Graham, Senior Editor of The Nature Briefing, has been keeping an eye on all the debates and discussions, and she joins me now. Flora, hi. Hi, nice to be here. Well, it's good to have you here to dive into the details. And so, as listeners are fully aware, urgent action needs to happen on climate change. And so every year, there are these COPs that happen where world leaders and negotiators gather together to try and assess how the world is doing.

And so in this 29th one, what were the key things that people wanted to hash out to try and keep the planet from dangerous levels of warming? Well, the goal of this year's conference was to hammer out climate finance. So this is the idea that rich nations have certainly done most of the emitting of carbon and other fossil fuel pollution. They have reaped most of the rewards of this industrial progress.

And yet the poorer countries that did so little of the damage tend to be most vulnerable to the effects of climate change. And, of course, they're being asked to decarbonize as well. And they have to figure out a way to pay for that while they adapt to the worst effects.

So the idea of climate finance is that the rich nations agree to fund some of the transition and decarbonization of the poorer places. Now, the current level of climate finance is about 100 billion U.S. dollars per year. At COP29, rich nations agreed to lead the call to raise 300 billion per year. And that's from 2035. Now,

Is it a good agreement? A lot of people are happy that any agreement got made at all.

It definitely went to the wire. A lot of the poor countries who are at the heart of the agreement say, you know, this is woefully insufficient. Estimates are saying the type of movement needed is going to cost more than, let's say, a trillion U.S. dollars. But the fact is, it is a significant increase, even taking into account inflation, since the last commitment of 100 billion U.S. dollars per year was made. And it does also include inflation.

a kind of softly worded agreement that countries will try to push this number up

by encouraging private funding to the target of 1.3 trillion. And this has been a topic in previous COPs as well, and it's been quite a big sticking point. So how were the negotiators able to come to this agreement in the end? What were the key roadblocks they had to get through? And why is it that some people find it still insufficient? Well, there was a really fascinating perspective on

from the president of COP29. So this is Azerbaijan's ecology and natural resources minister, who also spent a long career at the country's state-owned oil company. And he wrote a quite interesting opinion piece about the behind the scenes of how the agreement was met. Now, of course, you know, this is an opinion piece, take it with a grain of salt. But he argued that Western countries really stood in the way of a better deal for poorer countries.

So according to him, for example, China was willing to offer significantly more money if others would, but the others just wouldn't stand for it. At the end of the day, a lot of the draft texts were not released in good time to some of the poorer nations who are really at the core of the discussion. A lot of representatives of these nations expressed concern.

real dismay about not having seen the draft copy with significant time, a feeling that they'd been kind of railroaded into agreement to avoid, you know, nothing being agreed, which everybody feels would be ultimately, you know, a very dangerous precedent because it would undermine the whole concept of global action. And so we've talked a lot about the climate finance part of the negotiations. And

But what else came out of this particular COP? Well, it really was a finance COP in that the other really notable agreement that came out of it was a framework for a global market in carbon trading.

I'm sure most of our listeners are familiar that carbon credits and carbon trading, there's been a lot of concerns about the integrity of these schemes. Finally, we have what is hoped to be a global agreement on a mechanism that will be really useful for developing countries to raise money for the kinds of needs that we already discussed. It was a contentious topic. There was years of deadlock. So to finalize this and have some rules to move forward is a really big step forward.

And so I wanted to talk to you a little bit about the US as well, because they're the biggest economy in the world and one of the leading contributors to carbon emissions.

And obviously, in the previous Trump administration, the U.S. pulled out of the Paris Agreement and it's probably likely they will pull out again. What effect did this have on the proceedings? From what I've heard, it definitely cast a pall early on in the conference. But what expert observers told us at Nature is that

People felt that the agreement fundamentally didn't roll back anything that we already had. You know, we're moving forward. The progress is still happening. And so that puts us into a good place as climate skeptic leaders like Donald Trump are entering their positions.

elected positions. So I think one of the biggest concerns is that the U.S. is an absolutely enormous contributor to climate finance. Under the administration of U.S. President Joe Biden, the country was committed to providing more than $11 billion in climate finance each year, which is about 10% of the global total right now. So there is a concern, you know, that we

we're not going to see that continue under a Trump presidency. However, we did see other countries really start to rise to the fore. The United Kingdom has made no secret of the fact that under the new government, it wants to reassume its leadership in global climate ambition. And

as I understand as well, there were some pessimistic voices at COP. And from my reading, it seemed that they were asking, is this conference still fit for purpose? Absolutely. Although I wouldn't necessarily characterize it as pessimistic. I think it's people who are like, enough talk, this type of process is too slow for the type of risk that we're dealing with. So

So I think it's people who are very well aware of the progress of climate change, the speeding progress of climate change. And we're talking about people like climate scientist Johan Rockström. We're talking about, you know, leading climate figures. So in no way are they trying to put the brakes on movement. In fact, they're saying that let's shift climate.

From negotiation to implementation. And perhaps the COP process is not fit for that kind of purpose. That's the argument. And of course, I think that there's a certain argument that, you know, you need people pushing at the extremes in order to really communicate to the decision makers the strength of feeling and the objectively feeling.

enormous challenge. And it certainly is an enormous challenge and it's continuing one, not just at COPS, but throughout the rest of the year as well. So what should we be looking to as we go forward? Well, I would say the biggest thing we should try to keep our eye on is

OK, it's one thing to promise 300 billion per year. It's a very different thing to deliver. Now, the previous climate finance target, which was set in 2009 at COP 15, was 100 billion U.S. dollars per year and was meant to be delivered by 2020, but was not actually achieved until two years later. That really created a rift.

between poorer and richer countries that much of this year's contention kind of reopened those wounds. And I think that the countries relying on that finance are really looking to see whether that promise will be broken again.

And they're really looking to see, you know, this concession was so hard won and, you know, quite painful in a way for countries, some of whom like the vulnerable small island states. This is really an existential question for them. So how much is talk and how much is action? And so much of the agreement is undefined. How much is going to be grants versus loans based?

big difference between getting given money you don't have to pay back and money that you do. How much is going to come from the states? How much is going to come from the private sector? So there's a lot of questions that remain to be answered that really are going to show the proof in the pudding is in the eating. Yeah.

Well, I'm sure this is a particular pudding that we'll be eating going forward into the future. But I think that's all we've got time for now. Flo, thank you so much for joining me. Thanks for having me. And listeners, for more of Nature's COP coverage, we'll put some links in the show notes, along with a link of where you can sign up to the Nature briefing to get stories like that straight to your inbox. That's all for this week. As always, you can keep in touch with us on X. We're at Nature Podcast. Or you can send an email to podcast at nature.com.

I'm Emily Bates. And I'm Nick Petrichow. Thanks for listening. And

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