Podcast: Our reporters' top picks of 2018

Host: Benjamin Thompson

Welcome to a special round-up edition of the Nature Podcast, I’m Benjamin Thompson.

So listeners, here we are in the last full week of 2018, and I thought that this was probably the right time to have a bit of a look back at some of the stories we covered on the podcast this year. But rather than pick them myself, I asked a few of our regular reporters to choose their favourite podcast piece, and tell us why they enjoyed making it.

Later in the show you’ll hear from Lizzie Gibney and Shamini Bundell, but first Noah Baker tells us about his 2018 podcast highlight.

Interviewee: Noah Baker

The piece that I’ve chosen is from back in June and it’s stuck with me, I think, because I got the opportunity to combine, not only some really interesting science, but also some mystery and quite a bit of culture as well, which I don’t often the chance to do, or certainly don’t do as much as I’d like. So, there was a study in Nature Plants which was investigating these ancient, bizarre, gigantic trees called Baobabs, and I love Baobabs. I think they’re really incredible things, so that stuck out to me quite quickly when I saw the press release. But on reading the paper, it became clear that from my perspective there was a lot more than I might expect from a botany study: there was scientific mystery, there was a very real, and sometimes quite worrying, consequence to what was being said in the paper, which you’ll hear in a minute. And reporting on it took me in all sorts of directions, from the economic impacts of Baobab trees through to the folklore surrounding them, and the importance of them to many African peoples across the continent. And one of my contributors, Witness Konzanayi, even recorded a song with his family on his phone and sent it to me via Whatsapp and it ended up in the piece. It was a wonderful experience for me, I learnt a lot and I hope you enjoy it.

[Witness and family singing a traditional song about the baobab]

Interviewee: Witness Konzanayi

Growing up we would name the baobab trees after, you know, maybe after their shape. If it is too ugly, say ‘this ugly one’, if it produces a fruit or sweet foods, we’ll say this one is ‘sweet mama’.

Interviewee: Chris Surridge

The baobab is a completely unique tree in lots of respects, those sort of massive trees that are just about as wide as they are tall. It’s probably the oldest lived, it’s certainly the largest of the angiosperms, these flowering plants.

Interviewee: Witness Konzanayi

It is a tree that every child will identify with.

Interviewer: Noah Baker

If you picture an African savannah, more likely than not you’ll picture a baobab tree. A solemn giant, somehow bulbous and spindly at the same time, often described as growing upside-down. Now, new research investigating the age of baobabs has shown that many of the largest and oldest trees in the world are dead or dying, and scientists don’t know why.

Interviewee: Witness Konzanayi

Once upon a time, a long time ago, the Creator invited all animals to his office so that he could give them trees, you know seedlings for planting.

Interviewer: Noah Baker

That’s Witness Konzanayi from the University of Cape Town in South Africa. He’s just finished his PhD on the governance of the baobab.

Interviewee: Witness Konzanayi

And the hyena of all animals was very lazy and he went to the Creator very late, and when he got there the only seedling that was left was that of a baobab tree. And he didn’t impress the hyena, so in anger the hyena took the seedling, threw it far away. That’s what happened, that’s how the baobab ended up with such an ugly shape.

Interviewer: Noah Baker

There are countless folktales like this one, each surrounding the baobab, many explaining its bizarre shape. Here’s Chris Surridge, the editor of Nature Plantswith the scientific version.

Interviewee: Chris Surridge

Normally, trees grow, they have a trunk, and they pretty much have one trunk and they split off further up into branches. Now baobabs are a bit weird in that they through their life can produce additional trunks that come up out of the ground. You sometimes see suckers come out of things like blackberries, but trees do not do this. But the baobab does, it throws up these extra trunks, a ring of stems which then fuse together to form this empty centre. They become sort of circular but with a gap in the middle.

Interviewer: Noah Baker

This is the leading theory for how baobabs have ended up so fat, and also explains why, more often than not, they have huge cavities inside. This bizarre architecture leads to problems if scientists want to find out how old a tree is.

Interviewee: Chris Surridge

Normally, when you try and date a tree you have to chop it down and count the rings into the centre, or you put a bore in and you can do that and check these. But there’s no centre to a baobab tree.

Interviewer: Noah Baker

So, when researchers decided to measure the age of the largest baobabs known across the African continent, they had to turn to another method. Here’s Adrian Patrut from the University of Babeş-Bolyai in Romania.

Interviewee: Adrian Patrut

The only possibility to date a baobab is actually to radiocarbon date samples collected from each stem.

Interviewer: Noah Baker

Radio carbon dating is not uncommon when dealing with very old trees. In fact, trees are often used to calibrate carbon dating methods – because counting tree rings is such a reliable way of measuring age, it can be used as a solid point of comparison. Adrian Patrut’s team started surveying trees in 2005, and some of those they surveyed were truly ancient.

Interviewee: Adrian Patrut

The oldest trees were around 2,000 years old, and we found a specimen in Zimbabwe, the so-called Panke baobab, and we collected samples which were up to 2,450 years old.

Interviewer: Noah Baker

These are trees which sprouted before Aristotle even proposed the division of the sciences. Trees which were already centuries old when Julius Caesar took the throne in Rome.

Interviewee: Chris Surridge

This is just an incredible age. Trees are happy to grow for hundreds of years, but getting up to these sorts of millennial ages is something that the flowering plants and flowering trees just don’t do.

Interviewer: Noah Baker

It’s worth noting here that there are non-flowering trees which are even older. Now, when a baobab gets really large or old, it can take on a particular significance. Here’s Witness again.

Interviewee: Witness Konzanayi

To an African person who identifies with these trees, once a tree becomes this big, it becomes sacred. They become more venues for spirits of the land.

Interviewer: Noah Baker

This significance adds even more weight to another discovery that Patrut and his team made.

Interviewee: Adrian Patrut

It was very unexpected to find that many old and large trees die in a very short timespan.

Interviewer: Noah Baker

Specifically, they found that 9 of the 13 oldest trees measured, and 5 of the 6 largest trees, have all died in the last 12 years. Now, these trees are all spread across Africa, sometimes thousands of miles apart. There was no sign of disease and the revered trees are usually very well cared for – they all even had names. It therefore seems too much of a coincidence that all of these deaths could happen by chance so suddenly. In fact, Patrut claims that it’s impossible.

Interviewee: Adrian Patrut

Scientifically it is impossible for trees which have an age limit of over 2,000 years to die in such a large number over a such short timespan.

Interviewer: Noah Baker

It begs the question then – what’s causing the deaths of these Baobabs?

Interviewee: Chris Surridge

The obvious conclusion is that it’s something environmental, something to do with changes in climate. But again, that’s very difficult to nail down because over 2,000 years these trees have seen a great deal of climate. I mean, they’ve lived through the Little Ice Ages that happened in about the 1400s, 1500s, so they’ve seen much colder temperatures than now. They’ve seen droughts, they’ve seen practically floods, and yet they have carried through that. It is true that as far as we can tell, the temperature in these areas is warmer now than it has often been in the past, and it is also quite dry at the moment so maybe this is going on. But we really don’t know what it is that is killing these trees, if indeed this is an unusual amount of deaths.

Interviewer: Noah Baker

It’s an interesting scientific mystery. As an academic who works with the baobab, Witness too was intrigued, but for him speaking as a Zimbabwean, the findings also represented something else.

Interviewee: Witness Konzanayi

To ecologists it is just the dying of trees, but to an African person the death of such big trees means the death of culture, it means the death of identity, it means the death of spirituality.

[Witness and family singing a traditional song about the baobab]

Interviewee: Witness Konzanayi

Increasingly I think people are getting to know about climate change, even in the modest areas, in fact you don’t need to be told – you live it because you see your leaves are drying, we experience floods every year. But what I’m not sure of is if people are able to relate the deaths of these trees to climate change. If the big trees are dying I think what we need to do is to quickly establish what the cause is, because for some communities, the baobab tree defines who they are.

[Witness and family singing a traditional song about the baobab]

Host: Benjamin Thompson

That was Noah’s pick of 2018, from our 14th of June show. In it you heard Witness Konzanayi from the University of Cape Town, Adrian Patrut from University of Babeş-Bolyai, and Chris Surridge, the editor-in-chief of Nature Plants. The song you heard was performed by Witness, along with his wife and children.

<Sting>

Host: Benjamin Thompson

The next of our 2018 selections was chosen by Lizzie Gibney. Lizzie has covered a bunch of physics stories on the podcast this year, looking at the pressure on the inside of a proton, and finding out the latest about graphene superconductors, to name just two. But for this show, she’s picked an interview she did with an award-winning scientist…

Interviewee: Lizzie Gibney

The piece that I have chosen is an interview with Nobel Prize winner Donna Strickland. She, as many people will have noted, was the third woman in history to win a Nobel Prize in Physics. But much more than that, she is just a brilliant and interesting person. So, her discovery was in the field of lasers and it was a big fundament advance but also has loads of applications. And she just was the most humble and sociable seeming person that I’ve ever seen win a Nobel Prize, I think. Interviewing her really made me feel like I’d just like to go down and have a drink with her in the pub. She was very relatable, so she is definitely my favourite piece of the year.

Host: Benjamin Thompson

So listeners, first broadcast on our 10th of October show, here’s Lizzie’s interview with Donna Strickland.

Interviewer: Lizzie Gibney

So first off, congratulations!

Interviewee: Donna Strickland

Thanks very much.

Interviewer: Lizzie Gibney

I understand that if we take you back to last Tuesday, the call from Stockholm was something of a surprise?

Interviewee: Donna Strickland

Of course, it was a total surprise, yes. And it was also 5 in the morning, so…

Interviewer: Lizzie Gibney

And the research that you won for was done in 1985, while you were a PhD student experimenting with lasers. What was it that you were trying to achieve at the time?

Interviewee: Donna Strickland

My PhD project was actually doing something that required a high-intensity laser. It was supposed to work in a way that many, many photons of light would interact with an atom all at the same time. And to do that you need to have all of your photons squeezed into small volume and that means you focus it with the lens down and you also squeeze in time. And so that’s what we were trying to do, but unfortunately, if you do that inside your laser it blows up. And so the idea came around to say okay, what we have to do is not squeeze all the pulses first, stretch them out so that it’s over a great big volume, amplify it up and then when we have all of the photons in the great big volume, you can squeeze it back down to a small volume, and now you have a really intense source of light.

Interviewer: Lizzie Gibney

And why is it that you wanted to improve the intensity of the lasers?

Interviewee: Donna Strickland

Well we wanted to interact with atoms in new ways and this type of laser can now have a force on an electron that’s bigger than the force that holds the electron to the atom. And also, it can be done very shortly and so the electrons simply fly off the atoms when they’re inside these laser fields.

Interviewer: Lizzie Gibney

So, if they’re a greater intensity that’s useful both in physics but also for applications including corrective laser eye surgery?

Interviewee: Donna Strickland

So, when people get this corrective surgery, people would actually scalpel off the outside part of the cornea, and then they would use the UV laser to reshape the cornea into new shape so that you could see and then put the flap back. What the ultrafast laser does is that because it doesn’t have to just cut from the surface, it’s only at the intense focal point that it does this damage where the electrons come off the atoms, you could actually put your laser and scan it over your cornea and it would cut underneath that. Instead of using a metal scalpel you can use a laser.

Interviewer: Lizzie Gibney

Sounds like a much less painful process.

Interviewee: Donna Strickland

That’s right, and it can be very precise with the laser.

Interviewer: Lizzie Gibney

Now, I wish we didn’t have to talk about gender. I’m sure that’s a topic that you’ve spoken about a lot this week, but as you’ll be very well aware, you know, you’re of course just the third woman to win a Nobel Prize in Physics. I guess first off, do you think that women are currently underrepresented among the Nobel laureates?

Interviewee: Donna Strickland

Well, 3 in 100 years or something – I think there are a higher percentage of women doing fantastic science than that, so probably we are underrepresented by the Nobel Prize, yes.

Interviewer: Lizzie Gibney

Lots of people have asked you about being a woman in physics, and I think that you said so far that you have always been treated fairly and paid well.

Interviewee: Donna Strickland

Actually, the University of Waterloo is always very careful. At one point, I got this letter, you know, saying that, “We look into making sure that women are paid equal but we realised…” And then a whole long line at the very end was, “And you were being treated equal so you won’t get a raise.” And I went well too bad because I would have liked the raise but at least I’m being treated equal! So that’s the way it is.

Interviewer: Lizzie Gibney

Well that’s really good to know. And much has also been made of the fact that you are an associate professor rather than a professor, and I think you’d said that you’d never applied, is that right?

Interviewee: Donna Strickland

Yeah, now I really wish I just had. I had colleagues that were saying, “Why aren’t you applying, you should be applying.” And I sort of just said, “Okay, I’ll probably do it next year.”

Interviewer: Lizzie Gibney

And to get a bit meta, obviously, you know I started these few questions by apologising for asking you about the very fact that you’re a woman. How has it felt over the past few days answering so many questions on that topic?

Interviewee: Donna Strickland

I do hope that we do get to the point, we all hope we get to the point where this just becomes not discussed anymore. I mean, so hopefully soon there’s enough women and enough people of colour and enough of every group out there that feels that they get the recognition they deserve, and then we don’t have to talk about it anymore.

Interviewer: Lizzie Gibney

Any suggestions on how we can reach that point, either what advice to younger scientists or even to the Nobels as to how to make the system work better?

Interviewee: Donna Strickland

I think we’ve been pushing for a lot of years and I do feel like women’s lib was talked about a lot in the 70s and I certainly always felt that, you know, as a woman, I could do whatever the heck I wanted. You know, and maybe a lot of women who felt that got out there and did it and maybe we let it slide again. Certainly, this is a moment in history where women around the world aren’t letting much slide anymore, so I think things are changing again, fairly quickly again. Question is whether we can consistently keep moving forward until it’s all done.

Interviewer: Lizzie Gibney

And Donna, you now have an incredible platform from which to speak, being a Nobel laureate. How do you plan to use that?

Interviewee: Donna Strickland

I don’t know! It’s kind of a scary kind of thing because I am somebody who just talks a lot without thinking and people have been quoting me back and I think did I actually say that? So that’s got me a little scared. I will have to practice not just saying the first thing that comes into my mind.

Interviewer: Lizzie Gibney

And how has your life changed since becoming a Nobel laureate on Tuesday?

Interviewee: Donna Strickland

Oh, completely! This is just completely crazy and you know, I got to talk to the Prime Minister of Canada for the first time ever and he was very nice about it because I said, “This is like your life all the time.” And he said, “No, I don’t always get to speak to a Nobel laureate.”

Interviewer: Lizzie Gibney

Wow, well enjoy it! It sounds like it’s hectic but congratulations again.

Interviewee: Donna Strickland

Thank you very much.

<Sting>

Host: Benjamin Thompson

The final piece in this roundup is chosen by Shamini Bundell. In this case, she’s gone right back to the start of the year…

Interviewee: Shamini Bundell

So, I’ve chosen a pod piece that I vaguely remember – it was from all the way back in January. But it was actually about memory – see what I did there. And it was just some really fascinating science that we end up talking about, that you’re going to hear in a minute, all about how to actually manipulate memories, which I something that, really, I though should be in the realm of sci-fi. Have you seen that film Eternal Sunshine of the Spotless Mind? They go in, they, like, delete memories. Well this is about researchers doing something vaguely similar, but in mice.

Host: Benjamin Thompson

So without further ado, from our 11th of January show, here’s Shamini learning about the shape of memory…

Interviewer: Shamini Bundell

So there’s a feature out in Nature this week about memory. It asks what does a single memory look like? Where is it stored in the brain? Which cells are involved? And what determines its particular shape? I got in touch with a neuroscientist who’s working to answer these questions, Sheena Josselyn. I first asked her how scientists define a memory.

Interviewee: Sheena Josselyn

Everybody has their colloquial definition. I think we can probably all agree that it’s some sort of representation in the brain of a past event or some sort of past learning that we can recall at a later point.

Interviewer: Shamini Bundell

And when people first were studying memory, they were like, right, where’s the memory section of the brain? That must be where the memories are stored. But we’ve since come to understand that memories are more distributed across different brain areas.

Interviewee: Sheena Josselyn

We’re certainly not saying that there’s one specific cell that stores a memory, the grandmother cell. You know, you stimulate this cell and there’s an image of your grandmother. We, now, as a field, I think appreciate that memories are widely distributed in groups or ensembles of neurons that come together and for whatever reason these cells seem to be chosen, and not other cells, and they form a memory.

Interviewer: Shamini Bundell

And if there’s no one cell, we can’t identify the cell for a memory, how would we go about finding out which multiple cells or multiple areas are involved in any given memory?

Interviewee: Sheena Josselyn

We are still at the inference game. We infer that a cell or a brain region is important in a memory if we get someone to recall this memory and we see this brain area very active. So if you’re looking at human memory, you put someone in an FMR scanner and you ask them to recall a memory and those places that are more active, they have stronger blood flow, those are thought to be the ones that are really important in retrieving this memory and probably really important in housing this memory. We do the same kind of experiments on experimental animals in the lab.

Interviewer: Shamini Bundell

So you have this vague idea that there is an association there with this memory and these particular cells but how can you actually sort of test whether you’re right about that?

Interviewee: Sheena Josselyn

So we can ask what happens if we manipulate the activities of these cells when we ask mice to recall a memory and what happens if we decrease an activity? Can they still recall a memory? So we go in and we can kill just these cells we think are really important in the memory and we ask the mouse to recall the memory. The mouse shows us no evidence of recall. It’s as if the memory has been erased.

Interviewer: Shamini Bundell

How do you know if a mouse is remembering something or not?

Interviewee: Sheena Josselyn

Yes that’s a question that we spend a lot of time in the lab discussing and the only thing that we can do is we look at their behaviour. So, when a mouse is afraid, it shows this fear response. So it adapts this crouched, motionless posture. So what we do in the lab is we pair an innocuous stimulus such as a tone or a place with a tiny electric foot shock. Now it’s not enough to cause the animals any damage but it’s enough for the mouse to say, what the ‘huh’, and the cool thing is we can test memory by saying, well the next time that you hear this tone that we previously paired with the shock, do you show fear responses?

Interviewer: Shamini Bundell

And then the next step is to see if you can stop them remembering the association?

Interviewee: Sheena Josselyn

Absolutely. So, what happens if we perturb the function of this small population of cells? Do mice show us this freezing response? Do they remember? And it turns out that no they don’t so it’s like we’re sort of turning off the memory and the cool thing is, it has to be these cells we perturb the function of. If we perturb the function of a bunch of other cells, we don’t see this. So it’s really specific.

Interviewer: Shamini Bundell

So, getting rid of the memory is one way to prove that you’ve kind of got the right cells, you’ve found the cells for that memory, but then there are also experiments on activating recall of an existing memory?

Interviewee: Sheena Josselyn

I mean you can always argue that there’s multiple ways of decreasing a memory, but to actually bring a memory out of the air, to have the animal bring to mind a memory without giving it an external retrieval cue, so in this case the tone, what we can do is just give it an internal retrieval cue. We artificially activate these cells. It’s like we’re bring to mind this memory because the mouse freezes. So it’s like we’re cutting out the middle man, going directly to those areas of the brain we think are important in the memory, we cause the mouse to remember this memory and they show us this by freezing. It’s amazing that this experiment worked and that it’s been replicated so many different times.

Interviewer: Shamini Bundell

I mean it’s just really cool that you’re able to manipulate memories like that, but is manipulating memories either activating it or getting rid of it, is that actually the point of the research?

Interviewee: Sheena Josselyn

I don’t think that anyone is in this business to sort of cosmetically change memories. What we really want to do is understand how memories are formed in the brain for two reasons. One: it’s a really cool question. Our brains are sort of like the final frontier of science. It really tells us who we are and how we process information, how we encode information, is really looking at understanding the brain at a really fundamental level. But it’s also really important because there’s an epidemic of memory disorders in the world. Everything from Alzheimer’s to autism which you can sort of phrase as being an information processing disorder. But the treatments are really lacking because we don’t understand how memories are normally made.

Interviewer: Shamini Bundell

So your work is mainly on mice but the research that’s going on in humans is actually kind of backing up a lot of what you’ve found?

Interviewee: Sheena Josselyn

The fundamental things about how memory is encoded is really similar between mice and humans in the lab and to me if we get really converging evidence from two very different species doing very different tasks, yet the same answers still keep coming up, that is really exciting to me. It tells me that we’re really onto something here.

Host: Benjamin Thompson

So there we have it listeners, a few of the top stories from 2018, chosen by the reporters who made them. That’s it for this special roundup edition of the Nature Podcast, and in fact that’s it for this year.

Thanks to all of you for listening. We’re taking a little break, but we’ll be back very soon. In the meantime, if you want to hear more great science stories from this year, head over to Nature.com/nature/podcast where you’ll find all of our 2018 episodes.

I’ve been Benjamin Thompson, see you in 2019.