Podcast: Tropical cuckoo parasitism, topological materials, and cannabinoids in yeast

Host: Benjamin Thompson

Welcome back to the Nature Podcast. This week, we’ll be hearing about breeding strategies in tropical cuckoos, entering the weird world of topological materials...

Host: Shamini Bundell

And learning how yeast are being engineered to produce cannabinoids. I’m Shamini Bundell.

Host: Benjamin Thompson

And I’m Benjamin Thompson.

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Host: Shamini Bundell

First up, I’ve been finding out how to raise babies.

Host: Benjamin Thompson

Right, did you get some good child-rearing tips?

Host: Shamini Bundell

Oh yeah, so basically, your main priority as a parent should apparently be to have as many kids as possible and then get them to have as many kids as possible, so you can maximise your evolutionary fitness by multiplying your genetic material.

Host: Benjamin Thompson

Right, I’m sure my significant other will love that approach.

Host: Shamini Bundell

Well, you’ve actually got then a couple of options for different strategies within that. So, you could try the sort of frogs and fish kind of method, which is lay a bunch of eggs, abandon them, and then hope statistically that some of them will make it.

Host: Benjamin Thompson

Well, yes, that’s a strong strategy, sure. But what’s the other option?

Host: Shamini Bundell

Oh, put all your resources into a few offspring and then give them the best chance of flourishing.

Host: Benjamin Thompson

Yeah, I think I’ll probably go with that one.

Host: Shamini Bundell

Typical mammal. Actually, a lot of birds are quite into that strategy too so if you think about a little songbird sitting on her eggs to keep them safe and warm and then feeding the chicks until their nearly full-grown. To me that actually sounds like quite a lot of effort, but I’ve been finding out about a third option, and if you’re lazy like I am, it actually sounds quite good.

Interviewee: Christina Riehl

So, the common cuckoos lay their eggs into the nests of other species of birds, and so the baby cuckoo hatches and is cared for by members of a completely different species.

Interviewer: Shamini Bundell

So, that’s Christina Riehl from Princeton University. She’s interested in the evolution of this so-called ‘brood parasitism’ – when one individual acts as a parasite on the parental care of another. But the common cuckoo’s method of finding another species and hoodwinking them isn’t the only type of parasitic reproduction. Christina spends a lot of her time in Panama, where she studies another species of cuckoo called the greater ani. This bird has a different reproductive strategy. So, I called her up to find out more.

Interviewee: Christina Riehl

Greater anis are a member of the cuckoo family, but they look a lot like a small crow –they’re black and glossy, they have bright yellow eyes and they have long tails – and most of the time, anis nest communally. They nest in cooperative groups where several pairs build a single nest together and all the females lay their eggs in the same nest and all of the pairs in the group share parental care of the mixed clutch of young.

Interviewer: Shamini Bundell

Okay, so most of the time, the anis are raising their young cooperatively, and that all sounds very wonderful and harmonious, but your study was actually about the cases where that doesn’t happen.

Interviewee: Christina Riehl

There had been anecdotal reports of brood parasitism, so a female goes to a nest, dumps an egg, leaves and doesn’t provide parental care. So, what we wanted to do in this study was to understand why females act as parasites sometimes, and the benefits of acting as a parasite compared to the benefits of nesting cooperatively and taking care of your young.

Interviewer: Shamini Bundell

I feel like I would go for the parasitism route – that sounds way easier.

Interviewee: Christina Riehl

Right, it sounds easier, right? So that assumes, of course, that the benefits of parasitising are actually higher than the benefits of cooperating, and so we wanted to test that assumption by tracking the reproduction of females who do each of these strategies and try to understand if parasitism is so beneficial, then why is it that most females nest cooperatively?

Interviewer: Shamini Bundell

Right, and so for the study you had things like cameras watching the nests to see who was laying eggs and what happened to them, plus genetic testing of the adults, eggs and chicks, and what did all that reveal?

Interviewee: Christina Riehl

What we found was that most females in the population don’t start off as parasites. In the beginning of the nesting season, almost all of the females in the population join a cooperative group and they try to nest cooperatively and sometimes, in fact quite often, predators find the nests and they eat the eggs or the nestlings. And then that female is faced with a choice – she can either nest again in the same risky place where her eggs were just eaten or she can wait until the next year and just call it awash or she can switch to acting as a parasite. And what we found is actually it’s actually pretty hard to be a parasite. It’s not that easy because it’s true that you don’t have to pay the cost of parental care, but you have to find a host group, you have to put your egg in that nest at exactly the right time, and then you have to hope that that egg actually avoids predation and is raised alongside the host young.

Interviewer: Shamini Bundell

So, parasitism is not as easy as I might have assumed.

Interviewee: Christina Riehl

That’s right, it seems pretty hard to be a parasite – the timing, the success, and also the number of eggs. If a female nests cooperatively, she’ll lay three or four or five eggs in her own nest. To be a parasite and lay three of four or five eggs, that means you have to either visit the same nest repeatedly and put a bunch of eggs into the same host nest or you have to search and find a bunch of different host nests and lay one egg in each nest, and both of those things are pretty tricky to do. And what we found is it’s usually not a female’s first choice.

Interviewer: Shamini Bundell

I guess that seems like a relatively simple strategy. They’ve got this cooperative strategy, but if it goes wrong then they sort of resort to parasitism. Is it that simple?

Interviewee: Christina Riehl

Almost, that’s one part of it. The second part though is that some females do this repeatedly. So, we have a long-term dataset from the same population, following the same females over several years, and some females readily act as parasites when their nests are destroyed, and year after year you find their eggs turning up in other nests nearby. And other females never do this even though their nests might be destroyed by predators too. And so, the second part of the story is that when we looked at the overall reproductive success of those two different kinds of females, we found that it was pretty equal. So, females that never parasitise tend to lay slightly more eggs in their own nests than females that do sometimes act as parasites, so it’s essentially a question of where you put your eggs. Do you put them all in your own nest, all in one basket, so to speak, or do you spread them out and spread the risk? And it seems like there are two distinct types of strategies and that the success rates of both of them are about equal.

Interviewer: Shamini Bundell

And actually, neither strategy seems particularly easy because even with multiple adults around a nest, it’s still tough to protect the chicks and the eggs. There was one video that you got from a camera over a nest that shows a snake sort of sneaking in and swallowing an egg.

Interviewee: Christina Riehl

Yeah, that’s right. I mean I think nest predation really drives a lot of why the anis breed cooperatively as well as why they act as parasites. It’s a tough world out there. It’s hard to raise young. Eggs are very tasty things. Monkeys like to eat eggs, snakes love to eat eggs and so a lot of the different aspects of the anis’ life history from where they nest on the water’s edge to how they nest in groups or when they act as parasites all comes down to how hard it is to avoid predators and to raise young that are not eaten by snakes.

Interviewer: Shamini Bundell

That was Christina Riehl of Princeton University in the US. You can find Christina’s paper at nature.com/nature, along with a News and Views article. And we’ll be tweeting out some of the nest camera footage so you can see this fascinating bird for yourself. Follow us on @NaturePodcast for that.

Host: Benjamin Thompson

This week, Nature has three papers detailing a faster way to search for so-called topological materials. Now, these materials can have some fairly odd properties, so Luke Fleet, one of the senior editors here at Nature, popped by the studio to give me a little overview of the new work. We’ve covered topology on the show before, but I thought it best to get a refresher, so I started by asking Luke the obvious question: what is topology?

Interviewee: Luke Fleet

Topology is a branch of mathematics that basically is classifying things, and the thing to take from that is that there are some classes of materials that share properties because of some global parameter, so whether it’s got a hole in it or not or whether it’s got two holes or three holes. So, the key thing for topology is to think big scale, global properties. It’s not about the details; it’s about the bigger picture.

Interviewer: Benjamin Thompson

And how does this relate to materials and material chemistry?

Interviewee: Luke Fleet

If I connect it to maybe not materials but let’s say physics. So, topology, to some extent, does have a long history in physics. So, it was realised many decades ago now that inside materials that can conduct electricity – so you have electrons moving freely around – if you apply a magnetic field, then the electrons will start to curve, and if you apply a very, very strong magnetic field, then the ones in the middle will just be kind of running around in circles. So, then the system in the middle won’t be able to conduct electricity anymore because the electrons are just kind of running around themselves, but that’s not the case on the edges. So, on the edges, they can’t complete a full circle because there’s an edge there, and what actually happens is that they can bounce along the edges so then in the middle you don’t have any conduction – it’s just an insulator – and on the edges, you then have electrons running around the edges. And the connection to topology is that actually then you have in a system where on the edge you can have one electron running around – so the topology class, if you want, you can say it’s got one electron – but then there are situations where you can have two electrons and then three electrons, so there are discrete numbers and then you can think of them as different topological classes. So, all of the systems that have one electron running around have something in common because we haven’t spoken about what the material was – that’s the beauty about topology is that it doesn’t matter what the material is as long as it’s got certain properties.

Interviewer: Benjamin Thompson

And these properties can be quite particular. I mean you’ve described there something that appears to be both an insulator and a conductor at the same time. Is that why researchers are interested in these materials?

Interviewee: Luke Fleet

When they were first discovered I think a lot of people were really thought that they were odd, but they’ve got a lot more odd. So, as well as having electrons running around on the surface, there are ways that you can engineer this so actually the electrons are maybe confined to the corners, and also there are not just electrons. So, you can actually engineer quasiparticles that particle physicists could never even dream of. There’s a lot of excitement for a reason.

Interviewer: Benjamin Thompson

But as I understand it, only a handful of these topological materials have been studied in detail and not that many more are known about. Why is this the case?

Interviewee: Luke Fleet

This field – although the history you can connect back a few decades – it’s really only exploded since 2006-2007, and the reason was that we didn’t necessarily have good methods for predicting topology. No one really understood what conditions you needed to actually get materials with certain topological classifications. It’s only over the past few years that people have started to develop methods that would actually allow you to calculate whether a material would have the kind of properties that would be connected to topology. And there are a couple of good methods now, so people have been able to one-by-one kind of search through for more examples of materials that would have the necessary properties to be topological.

Interviewer: Benjamin Thompson

And I think this week is maybe a step forward then in the search for these topological materials – we’ve got not one, not two, but three papers in Nature describing new ways to look for them.

Interviewee: Luke Fleet

Yeah, that’s right. The authors have developed algorithms that can scan through the databases that exist, which catalogue all the crystal and graphic structures that we know of or have been predicted, and they apply the methods that have been very, very recently developed for calculating whether something will be topological or not. And they’ve gone through the database and had a look to see how many of these materials are topological. Their methods don’t work for every material – they can only be applied to a subset and that’s mostly connected to magnetism actually. Magnetism makes things very difficult so they’ve had to focus on the non-magnetic materials for now. But even so, that gives you tens of thousands of materials inside these databases that they can actually look at.

Interviewer: Benjamin Thompson

And how many non-magnetic materials have they found that might have topological properties?

Interviewee: Luke Fleet

A phenomenal number, considering just over a decade ago we really had a handful of materials that people knew were topological. These authors have discovered that maybe one in five or maybe one in four of all non-magnetic materials that are in these databases could be topological, which is just stunning.

Interviewer: Benjamin Thompson

I mean that’s a huge sort of step up. What does this mean for the field?

Interviewee: Luke Fleet

For the field as a whole, I think these papers are hugely important because they show topology is not some kind of niche subset of materials science. Materials are topological or do have topological properties in them, many materials have them. Whether a material exhibits interesting properties because of the topology, I think that’s a different question, but I think now it shows that topology really needs to be taken into consideration when doing materials science.

Interviewer: Benjamin Thompson

Well, what are the next steps? I mean, Luke, thinking that something might have topological properties in a computer and actually sort of physically getting it in your hands and probing it in lab are two very different things I imagine. What are the next steps that need to be taken?

Interviewee: Luke Fleet

We need to narrow the number because at the moment there’s just thousands and thousands of materials that have been predicted and not all of them have actually even been realised experimentally at the moment. But even if you can realise a material, defects are always a problem, and if a material is synthesised and it has a lot of defects, it might be that they drown out the interest in topological properties, and so that may be something that plagues quite a few of these materials. But there’s plenty to choose from, so even if a subset can’t be synthesised experimentally or maybe can’t be synthesised very purely, that’s not an issue. We can maybe move on to something else.

Interviewer: Benjamin Thompson

Well, finally then Luke, what sort of things might these materials be useful for in the future?

Interviewee: Luke Fleet

They can be useful for a lot of things. This is still the very, very early stages for applications but the potential number of applications is phenomenal. It could be we could use them for electronic devices or for things when we’re shining light or when you need a response to heat or maybe when doing catalysis. Because we’ve had so few materials, we haven’t really been able to exploit them for any large-scale applications at the moment, but now that the catalogue of materials available and the catalogue of properties available has exploded so much, I think it’s just a matter of time before someone can really exploit them in applications.

Interviewer: Benjamin Thompson

That was senior Nature editor Luke Fleet. You can find the three papers we talked about over at nature.com/nature. You’ll also find an Editorial and a Comment piece about topological materials over at nature.com/news.

Host: Shamini Bundell

Coming up in the show, we’ll be getting the latest on the CRISPR gene-edited babies story that broke back in November – that’s coming up in the News Chat. Now though, it’s time for the Research Highlights read this week by Anna Nagle.

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Anna Nagle

Strawberries are a quintessential part of British summer time, but new research suggests that they have global origins. The team behind the work have been delving into the garden strawberry’s complicated genome. Their work shows that several strawberry species hybridised with one another over a million years ago, beginning the ancestry of today’s crop. The fruit’s foundations appear to start with a cross between two species of Japanese strawberry. A plant of this lineage then bred with a strawberry species widespread in Europe and Asia, before a final North American subspecies was thrown into the genetic mix. It was this contribution from North America that the team thinks gave the garden strawberry its distinctive flavour, colour and aroma, resulting in the fruit we know and love. Read this sweet research over at Nature Genetics.

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Anna Nagle

Making a glowing gas of charged particles known as plasma by microwaving grapes has been a YouTube favourite for years. Now, researchers appear to have solved how this phenomenon actually happens. Plasma is produced when a grape is cut almost in two, leaving it held together by a thin slither of skin. It was thought that this skin acted as a moist antenna for microwaves and that plasma flared from this spot. Researchers from Canada used thermal imaging and computer simulations to show that in fact, the grape halves form a cavity which absorbs and focuses the microwave radiation in to a hotspot where the halves touch each other. It turns out that grapes aren’t really needed at all. The researchers were also able to produce plasma by microwaving two beads of almost pure water, which formed a familiar hotspot where the beads touched. Spark your curiosity over at the Proceedings of the National Academy of Sciences.

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Host: Shamini Bundell

Next up in the show, Nick Howe has been discovering how brewer’s yeast can be engineered to produce the active ingredients of cannabis.

Interviewer: Nick Howe

Cannabis has now been fully legalised in Uruguay and Canada. In the US, it’s legal in several states, and many countries have authorised it for medical use. Indeed, the US Food and Drug Administration (FDA) recently approved a cannabis-derived drug to treat epileptic seizures. There’s growing research interest in identifying potential applications for the active ingredients of cannabis, in particular cannabinoids such as cannabidiol or CBD and tetrahydrocannabinol or THC. Unfortunately for interested researchers, cannabis is difficult to work with. In many cases, there are restrictions when it comes to using the plant itself, and it only produces small amounts of the active ingredients. For these reasons, many biotech startups have been working on producing semi-synthetic cannabinoids – ones that are produced in organisms other than the original plant – in organisms such as yeast and bacteria. Journalist Elie Dolgin has been reporting on some of these startups.

Interviewee: Elie Dolgin

There’s at least a half-dozen companies now that are all trying to make these cannabinoids in yeast, in bacteria, in algae or even in cultured cannabinoid cells growing in suspension. So, this idea of lab-made semi-synthetic cannabinoids is really growing up.

Interviewer: Nick Howe

There are many claims and patents for possible production processes, but there has been sparse scientific evidence for a complete production process, until now. This week in Nature, a paper has described how to produce cannabinoids in yeast. I spoke to Jay Keasling, from the University of California Berkeley, one of the authors of the study.

Interviewee: Jay Keasling

The purpose of the paper was to describe our work importing the pathway that naturally produces cannabinoids in cannabis into yeast. One of the important aspects of our paper is that a key step in the biosynthetic pathway, which had been described in the pattern literature but never in the scientific literature, wouldn’t work when we imported that enzyme into yeast, and so we had to go back into cannabis and search for that key missing step.

Interviewer: Nick Howe

Once the team found the missing step, they were able to create the entire pathway. They can now feed their modified yeast a simple sugar and it will spit out cannabinoids. This is significantly cheaper and easier than producing cannabinoids by growing large numbers of plants. Another major benefit is that you can get a pure product and one you can control. Jay says this will help with legal restrictions, allowing researchers and drug companies to more easily investigate cannabinoid effects. Production of cannabinoids in yeast may also have other benefits.

Interviewee: Jay Keasling

What we discovered when we were building the biosynthetic pathway is that if we feed the cells hexenoic acid, we get CBD or THC depending on which synthase we have inside the cells, but we could also feed some completely unnatural acids, and this produces cannabinoids that have never been found in cannabis and probably don’t exist naturally, but that might be even better therapeutics when they’re tested for treating human disease. We don’t know that, but it gives us a whole range of cannabinoids that don’t exist naturally.

Interviewer: Nick Howe

These synthetic cannabinoids are complex molecules that are challenging to make with conventional chemistry. Making them with yeast is much simpler.

Interviewee: Jay Keasling

The more complicated the molecule is, the more challenging the chemical synthetic route is, and this is something that biology really excels at.

Interviewer: Nick Howe

So, scientists have made the pathway in yeast and it’s successfully producing cannabinoids. Can researchers and companies now make use of the technique? Elie thinks that this is just the first step.

Interviewee: Elie Dolgin

This still remains very much a proof of concept. The types of yields that the Keasling group here is reporting are very low, milligrams per litre. And to be actually price competitive or even just useful on an industrial scale, they need to ramp that up at least a hundredfold. The numbers I’ve heard is just to be price competitive with something like CBD or THC, you need to be producing grams per litre and this is milligrams per litre.

Interviewee: Jay Keasling

We’ll have to further optimise the pathway so that we produce large quantities of the desired final products, and then most of our work was done in shake flasks in the laboratory, but that’s not how you’ll produce it in large scale. You’ll use fermentation tanks that are like what you would find in a brewery when they brew yeast to produce ethanol from sugar, and so you can’t just go from a shake flask directly to a tank that’s 100,000 litres – you have to take intermediate steps. You’ll take it through a 1-litre, and a 10-litre and a 100-litre and a 1000-litre tank until you get it up to that large scale.

Interviewer: Nick Howe

There’s still quite a long way to go. As production scales up, there may be other problems too, like the yeast getting poisoned by chemicals it’s producing. But Jay thinks that there are ways around these problems and he predicts that in a few years will be seeing yeast produced cannabinoids on the shelves. We’ll have to wait and see, but Elie thinks that we should get used to the idea.

Interviewee: Elie Dolgin

I think this will increasingly become almost the norm for some of these things. The parallel that some people make is to the way that we get aspirin. Originally this was a molecule that was found in the white willow tree I believe, but we don’t grow orchards full of those trees anymore to get the painkiller out of the park, we make it in biotechnology fermentation tanks, and I think increasingly that this will probably be true of some of these cannabis-derived therapeutic molecules.

Host: Shamini Bundell

That was Elie Dolgin and Jay Keasling talking to Nick Howe. You can read Elie’s news article at nature.com/news, and Jay’s paper at nature.com/nature.

Interviewer: Benjamin Thompson

Speaking of news, it’s time for the News Chat and I’m joined on the line from Shanghai by David Cyranoski, Nature’s Asia-Pacific correspondent. David, thanks for joining me.

Interviewee: David Cyranoski

Hi Benjamin, thanks for having me.

Interviewer: Benjamin Thompson

Well, David, three months have passed since a huge news story broke about the CRISPR gene editing of two baby girls. For those of our listeners who perhaps don’t remember the ins and outs of this story, could you maybe give us a quick overview of what went on?

Interviewee: David Cyranoski

Well, a researcher in southern China announced that he had gene edited two embryos and that they had produced live births, which was something that no one really expected or wanted to happen, at least those in the scientific community. Here you’re introducing the gene edits at the very early stages of life, so they’re going to affect all the cells or most of the cells in these people with very unpredictable outcomes.

Interviewer: Benjamin Thompson

So, the researcher at the centre of this storm is He Jiankui, and David, you’ve written a News Feature that’s looking at some of the questions that remain to be answered as a result of his work. One of those questions is, of course, what’s going to happen to He Jiankui himself?

Interviewee: David Cyranoski

We’re not sure right now. I think China is really puzzling over what to do with him. One thing is for sure, that they’re quite embarrassed about the whole thing and they have been removing posts about He Jiankui from government websites and they’ve taken down news stories about him. Just after he announced all of this there was a state media news story boasting that this was another first for China and they seemed very proud of it, but since then that article was taken down and they’ve done a lot of censoring about this topic in China. So, one of the ways that his has been most evident I think is on social media, and the biggest social media application in China is WeChat. There’s a Hong Kong group that has been following this and they found that gene-edited babies were one of the most censored topics in China in 2018, so it’s clearly something that shows the embarrassment.

Interviewer: Benjamin Thompson

And what about these two baby girls, David? What’s the plan for their long-term care?

Interviewee: David Cyranoski

So, there’s a lot of questions about what the health of these girls is going to be and that’s going to be something that the Chinese government has to be looking into. I have not heard, and I’ve asked a bit to see if there is anything set up to give special treatment to these girls, I don’t know. I know one of the main things is they want to protect the privacy of these girls so it might be something that we don’t hear about, but I imagine that there are some doctors trying to figure out what kind of special tests need to be done and what kind of monitoring programme needs to be done to both ensure their health and to maintain their privacy.

Interviewer: Benjamin Thompson

Science, as we know, is rarely done by individuals – do we know if anybody else is involved?

Interviewee: David Cyranoski

Well, he clearly didn’t do it alone and he couldn’t have – he’s not a medical doctor. He had to have worked with doctors. I heard that he had a team of two embryologists and another ten or so technicians, but he was clearly the leader of that team and I think he’s being taken as the responsible person for that. But he also spoke with a handful of people outside of his own lab and his own project. And there has been, over the last three months, a great focus of attention on who knew what when because he talked to other prominent scientists in the field. And from what I can tell, almost all of them said hey, this is a terrible idea, you shouldn’t move forward with this. Some of them even said please don’t keep me in the loop about this anymore, I don’t want to know. And since then, over the past three months, there’s been a lot of soul searching in the scientific community about what to do with such knowledge. What do you do when another scientist, a peer of yours, tells you that they’re going to do something that you think is wrong and possibly dangerous with high risks? So, right now it’s really a burning question in the scientific community. Some people say well clearly, they could have done something – they could have gone to the media, they could have gone to other scientists, and others say well, who would they tell? Most of the people he told were overseas – I think all or most were in the United States. If you are in the US and someone from China says I’m doing this project but I have legal authority to do so, I’ve been approved for it, which he apparently told people, who are you going to tell as an American scientist? You can’t really call the police in China and say he’s breaking the law. So, the responsibility of scientists is one of the questions that’s being examined and one of the questions that I discuss in the piece.

Interviewer: Benjamin Thompson

If there is this potential difficulty with researchers reporting or whistleblowing, does this mean that this could happen again elsewhere?

Interviewee: David Cyranoski

I think everybody thinks it’s going to happen again. Whether it’s a better design trial, whether it’s done more transparently, whether it’s done with better safety is the big question, I think. Everybody wants to know how do you move forward with such a promising technology after such a debacle. That’s another thing that’s being sorted out now – the WHO have a committee that’s going to meet and try to come up with some recommendations on what to do. There’s no question that someone is going to try this. What people want is that it’s done in an open matter and it’s done when we’re ready for it.

Interviewer: Benjamin Thompson

Do you think this whole situation though might affect other strands of research that involve gene editing and what have you?

Interviewee: David Cyranoski

Yeah, there is a lot of talk about having a moratorium right now on this research and some people say well the only way to address this problem is just to say we won’t have any more of it. And there seems to be a split in the community of people who say a moratorium won’t work, for one thing because if you tell people not to do it there are plenty of people who seek the publicity of doing that. Unless you find better ways to enforce a moratorium, people aren’t going to be convinced that it’s going to work. The other problem is that it might affect that research that would be the kind of building blocks for moving forward with the technology. You can do a lot of basic research using CRISPR in human embryos that’s going to prepare you for eventually taking this to clinical use, and if you can’t do that because there’s a moratorium then you’re going to set the field back. So, there’s also a lot of researchers who are worried about that.

Interviewer: Benjamin Thompson

So, three months in, there’s still an awful lot of questions to answer then.

Interviewee: David Cyranoski

Yes, more, and they seem to be growing.

Interviewer: Benjamin Thompson

Well, thanks for joining me David. Listeners, you can read the full News Feature that goes further into these questions and more over at nature.com/news.

Host: Shamini Bundell

And that brings us to the end of yet another science-packed episode, but don’t forget to follow us on Twitter for some cuckoo clips among other things - were @NaturePodcast. I’m Shamini Bundell.

Host: Benjamin Thompson

And I’m Benjamin Thompson. Thanks for listening.