Host: Nick Petrić Howe
Welcome back to the Nature Podcast. This week: how having friends from different social classes could boost your wealth.
Host: Benjamin Thompson
And reviving pig organs after death. I’m Benjamin Thompson.
Host: Nick Petrić Howe
And I’m Nick Petrić Howe.
[Jingle]
Interviewer: Nick Petrić Howe
No man is an island, so the saying goes. We all live and work together in a society. And the connections, friendships and communities that we forge as we work and live together are something of great interest to social scientists and economists. In very broad terms, it’s what they call social capital.
Interviewee: Raj Chetty
So, the idea of social capital is one that’s been discussed by social scientists for more than 100 years, but I think the way in which it is defined has been kind of nebulous. People sometimes mean how tight-knit is a community or how much are people volunteering or to what extent are different types of people friends with each other.
Interviewer: Nick Petrić Howe
This is Raj Chetty, an economist who works on what kind of, and how many, economic opportunities – things like job opportunities – different people have. And that’s important because as nebulous as social capital is, it has been argued in recent years that having more of it could give people more economic opportunities. In other words, they may be able to get wealthier. However, as Raj points out, it’s been kind of hard to pin down what it is. And social capital has also proven very difficult to measure.
Interviewee: Theresa Kuchler
You basically need to know who is connected to whom. If you want to do that on a large scale, you need this information about a lot of communities and a lot of people in these communities. And that is just not something we've had any systematic information or data on.
Interviewer: Nick Petrić Howe
This is Theresa Kuchler, a big data economist who works on social networks. She and Raj have recently teamed up and published two papers in Nature, where they’ve analysed some of this large-scale data. To do so, they collaborated with Meta – previously known as Facebook – a place where they have a lot of information about how people connect to each other.
Interviewee: Raj Chetty
Yeah, so the scale here is really phenomenal. We're talking about data covering all users of Facebook in the United States between the ages of 25 and 44. That's about 72 million people. Just for context, those 72 million people represent about 84% of the US population between the ages of 25 and 44. And between them, those 72 million people have 21 billion friendships.
Interviewer: Nick Petrić Howe
I should say at this point as well that this data was deidentified, so there was no way to link it to any specific people. And actually, the team were interested in looking at it in aggregate – how do communities have connections with other communities? And with this, they could start to unpick how social capital affects people’s economic mobility, or to put it crudely, how easy it is for them to get richer. As I said though, it’s been hard to pin down what social capital is, so the team came up with three measures to describe it. One, social cohesion, or how many friends are friends with each other. Two, civic engagement – how much volunteering and things like that people do. And then finally, economic connectedness, or how many high socioeconomic status friends people with low socioeconomic status have, or again, to put it crudely, how many rich friends they have. Then they looked at how these three measures affect social mobility.
Interviewee: Theresa Kuchler
Amongst the different measures of social capital, it is really economic connectedness that stands out much more than anything else. It's just a really, really strong associate with economic mobility.
Interviewee: Raj Chetty
So, here's one way to think about it. So, on average, kids growing up in low-income families at present, 4 of their 10 friends come from high-income families. Now, in contrast, for high-income folks, about 70% of their friends are, in turn, high-income. So, consider the following hypothetical. Suppose, instead of growing up in a community where 40% of your friends are high-income, you grew up in a community where 70% of your friends are high-income, similar to where high-income kids are currently growing up, right? What we find is if people were to make such a move, their incomes in adulthood would rise by 20%.
Interviewer: Nick Petrić Howe
So, for those with below-median incomes, having friends with above-median income seems to be associated with significant increases in wealth later in life. But that does beg the question, why? What is it about having friends with higher incomes that that gives low-income people more economic opportunities? The team aren’t quite sure. They’ve only just found out that this association exists after all, but they do have some ideas.
Interviewee: Theresa Kuchler
So, for instance, you might think that what's one pathway to higher income in adulthood? It is going to college. And so, you could think that if you grew up in a community where low-socioeconomic-status children are more exposed to high-socioeconomic-status adults, then it might be easier for these children to learn about the fact that you can go to college. How do you go to college? How do you apply? So, it might be information about these career paths. It might be more directly that, in these communities, you hear about job opportunities. You hear someone is hiring and that’s how this works.
Interviewer: Nick Petrić Howe
However, it’s not quite clear yet. But one thing the team were able to work out is what are the factors that actually make people more connected in the first place? Regardless of how it works, what things are communities doing that mean that they’re making these friendships between people from different economic backgrounds. They uncovered two main factors.
Interviewee: Raj Chetty
The first we call exposure – the extent to which you actually meet people from different backgrounds. So, a necessary condition for having economic connectedness is exposure. But there's a second aspect that's equally important, which is what we call friending bias. Even if you and I go to the same school, we may not actually interact with each other.
Interviewee: Theresa Kuchler
You could think of it as if you commute, there's like thousands of people that you share a space in the subway with every single day. Probably the most of them you never talk to and most of them, you never would have a chance to become friends with because it's a setting where people don't really interact, in the sense that they would talk and find a reason or a way to make friends. And so, just kind of having people coexist in the same spaces doesn't mean that they form these connections, and it's obviously the first precondition of people never even exist in the same space, they obviously also cannot be friends. But just putting them in the same spaces doesn't mean that they necessarily become friends, so we need to think a little bit more than just putting people in the same school, in the same college and in the same neighbourhood, to also create opportunities for them to actually make these connections and become friends because only then do we see those benefits.
Interviewer: Nick Petrić Howe
Historically, there’s been a lot of focus on making sure people from different economic backgrounds interact. On the other hand, though, according to Raj and Theresa, there hasn’t been as much focus on increasing the likelihood that they actually become friends. But the data give them some clues as to how that could be changed.
Interviewee: Raj Chetty
We show that there's systematic variation across the settings in which people meet in friending bias. People are much more likely to make friendships that cut across class lines in religious institutions like churches and synagogues than they are in their neighbourhoods or in their colleges. Another example is that people are more likely to make cross-class friendships in smaller groups than they are in larger groups, or in certain types of high schools which are smaller. So, the point is that there are a bunch of institutional choices that we can make in the context of how we set up our schools, how large are they, how we make architectural and urban planning choices, whether we get different types of people to interact with each other or not, or just be in the same building in separate silos.
Interviewer: Nick Petrić Howe
One caveat to the work is it was based in the US on US data. Theresa and Raj suspect that aspects of this will be true the world over. Time will tell, and they are working on doing similar analyses in different countries. But they are hopeful this work will make an impact and help people get more opportunities.
Interviewee: Theresa Kuchler
I think, as a researcher, you obviously somewhat hope that your work will have some impact and that we learn something that can help people make better decisions. And I think there's a lot in this paper where I think policymakers can find ideas, guidance, and, first of all, some information about where their communities, where their schools, where their colleges stand, and I think that's a kind of very exciting thing to see that we can provide this information and hopefully help policymakers make better decisions. To that end, I do want to mention that we are going to make publicly available the economic connectedness and social capital measures at the community, high school and college level, so that each high school principal, every college president, can actually look at their own school and think about where, where they are, and where they might want to be, and whether they want to make adjustments.
Interviewer: Nick Petrić Howe
That was Theresa Kuchler, from the New York University Stern School of Business in the US. You also heard from Raj Chetty, from Harvard University, also in the US. For more on this story, check out the links in the show notes. And I’ll also put a link to socialcapital.org where you can explore the data for yourself.
Host: Benjamin Thompson
Coming up, we’ll be hearing how researchers have been working to restore functions in pig organs one hour after death. Right now, though, it’s time for the Research Highlights, read by Shamini Bundell.
[Jingle]
Shamini Bundell
How do you measure a ‘Venusquake’? The answer could be floating high in the sky. Earthquakes on the planet Venus, or ‘Venusquakes’, are hard to study. The planet has an average surface temperature of nearly 500 °C, meaning seismological equipment can’t survive long on the surface. Now, an experiment here on Earth could provide a solution: Earthquake-detecting balloons. Researchers have been analysing atmospheric pressure data from four high-altitude balloons. The balloons, flying at up to 20 kilometres high in the stratosphere, detected the low-frequency sound waves caused by a magnitude-7.3 earthquake that occurred near Indonesia in December last year. This suggests that fleets of balloons on other planets – such as Venus – could detect pressure disturbances in their atmospheres. The data would be useful for better understanding the planet’s poorly known internal structure. Find more on that high-flying research in Geophysical Research Letters.
[Jingle]
Shamini Bundell
A parasitic fungus that infects houseflies has an enticing trick for spreading to new hosts.
Entomophthora muscae is a fungus known to attack the brains of its host flies, manipulating their behaviour to help the fungal spores spread. Before the flies die, they’re made to climb to a high-up spot and perch with their wings outspread. This means the spores which explode from their dead bodies are more likely to encounter a new host to infect. Now, it seems that this fungus has an extra trick up its sleeve: enticing male houseflies to mate with the corpses of infected females. Researchers presented healthy male flies with dead females, some laden with fungal spores and some without. The males attempted to mate, preferring the infected females, and most of those males later became infected themselves. The fungus probably achieved this success by releasing smelly compounds similar to the flies’ usual chemical mating cues. If you’re drawn to this research, you can read it in full in the ISME Journal: Multidisciplinary Journal of Microbial Ecology.
[Jingle]
Interviewer: Nick Petrić Howe
In recent months and years, we’ve covered a few papers here on the podcast about reviving previously deceased tissues. In particular, you may remember one from back in 2019 where researchers revived functions in pig brains 4 hours after death. Well, now, the same team of researchers are publishing a new paper in Nature where they’ve done a similar thing, but with the whole pig, using a system called OrganEx. To find out more about this work and its potential impacts, joining me today is Max Kozlov, reporter here at Nature who’s been writing about this story. Max, how’s it going?
Interviewee: Max Kozlov
It’s going well.
Interviewer: Nick Petrić Howe
Well, I’m glad that you’re here with me now, Max, because this seems like quite a complicated story. And in the intro, I mentioned this is about sort of reviving dead tissues and that sort of thing, so I guess the first thing to clear up is what exactly have they done in this paper?
Interviewee: Max Kozlov
That's a good question because it's important to tell you that they haven't reanimated the pig. So, what they've done here is they've partially restored some of the function of the organs. And when I say organs, I mean, the heart, the liver, the kidneys and the brain. And when I say they've partially restored some of the function, I mean that they saw that the cells, which usually an hour after death are not doing too hot – they are kind of falling apart, they're spilling out, they're causing the organs to swell, and it's a whole mess. So, what they've done here is they have shown that they can actually still reperfuse, they can still run fluid through the entire body of the pig, and that it reaches pretty much every point in the body. Because what happens really quickly, without oxygen, cells start to die. And so, if you're able to come up with a technique that can restore oxygen to those cells, that can potentially halt some of these cascades of damaging effects to the body, and that's exactly what they've done here. Not only that, they were also able to show that the heart, for example, it wasn't beating all of a sudden, but they saw some electrical activity in the ventricles, which indicate that it's doing a whole lot better than it was without this treatment, which was pretty shocking to see.
Interviewer: Nick Petrić Howe
So, not maybe revived in the way we might think about it, but certainly there was an amount of function there. And so, I reported on the brain paper back in 2019, and what they did there is they use something called BrainEx to reperfuse the tissues with this sort of like artificial blood, with compounds that help sort of revive tissues to an extent. Is it basically the same kind of thing but just for the whole pig?
Interviewee: Max Kozlov
It is very similar, but there are some important differences, mainly in that the brain is just one organ, whereas what they've done here is something that has to work for the entire body. So, some of the compounds that they include in this – they call it perfusate – liquid solution are different in that the brain is kind of a weird organ where the immune system doesn't have as much of an effect there and it just behaves very differently than other organs. So, what they've had to do here is scale up their entire approach. They needed a much more powerful machine to deliver this solution to the entire body rather than just one organ that's outside of the pig's body. And specifically, they had to find compounds that would work universally for every organ, which I can imagine was not very easy and took a lot of trial and error.
Interviewer: Nick Petrić Howe
I mean, as you say, this seems like quite a significant challenge, like how many pigs were they able to get this working in?
Interviewee: Max Kozlov
It’s a little bit actually unclear in the paper to be honest. It says that they used up to 100 pigs, and specifically I believe it said that 31 pigs were used in the data, whereas the other pigs were used to kind of refine the technique.
Interviewer: Nick Petrić Howe
But they were able to do this a number of times it seems.
Interviewee: Max Kozlov
Yes, yes, and specifically, they compare this technique with pigs that received no treatment, and then something called ECMO that is currently used in hospitals around the world to try to resuscitate patients and keep patients alive. And in some cases, it’s even used after death to keep organs viable for potential transplantation. And what they found is, across all of these different metrics that they measured, OrganEx fared a lot better than both no treatment and ECMO, which made a lot of people that I spoke with very excited, especially people who are in the transplantation world.
Interviewer: Nick Petrić Howe
So, what were these people saying about this? Could this be a way to get more transplants?
Interviewee: Max Kozlov
Yes, it definitely could be, but it's important to remember that this is just the first study that has demonstrated this, and it's, more than anything, a proof of concept. And one, they'd love to see these results replicated. And then of course, if these organs are actually viable for transplantation in animals and then potentially one day, if that's successful, move on to humans. But it's important because, as I mentioned earlier, the body starts to shut down very quickly after death. And so, if there's a way to prolong how long organs are viable for after death, that could be a really useful strategy to alleviate the extremely long waiting lists that a lot of countries have for organ donation. At the same time, though, some of the bioethicists I spoke with were also very excited about this prospect but they wanted to make sure that this research was being done in a responsible way, in that there are potential considerations to think through before this is rolled out tomorrow or anytime soon because the practice of even using ECMO to preserve organs after death is already controversial in some places, and this pushes the envelope on how long after death organs might be viable for.
Interviewer: Nick Petrić Howe
And I remember, again, when we were talking about the brains back in 2019, it caused like questions even on like the nature of death itself. Have you come across similar sort of ethical quandaries with this work?
Interviewee: Max Kozlov
Yes, and it’s because there are two types of death that researchers talk about and that are even codified in law. One of those is brain death and the other is heart death. So, in the 2019 paper, they challenged this notion of brain death. And now they've kind of challenged this notion of heart death, which we already saw signs of with, for example, CPR – you can call that challenging heart death – or other techniques to revive a person. But it's another thing to do it an hour after death, and that was really the main finding here is that that irreversibility can be challenged an hour after, and that irreversibility is currently the working definition of death. But what they've shown here is that it might still be possible to reverse something like cardiac death, so long after death, which was really surprising to a lot of researchers I spoke with. But again, it's important to note that they didn't see any kind of organised brain activity that would indicate that the animals have somehow regained consciousness or sensation or anything like that. But some of the ethicists I spoke with said it's really important that future researchers do their due diligence to see if there's any kind of restoration of brain function because that's important for researchers to understand so they can know how to proceed with this kind of research in the most ethical possible way.
Interviewer: Nick Petrić Howe
And so, do you have a sense from the researchers or from the people you spoke to about what should happen next with this work?
Interviewee: Max Kozlov
Yeah, in the paper, they noticed that only the pigs that received OrganEx showed some involuntary movement of the head, neck and torso, when they injected those pigs with a dye to see what their brains looked like. The pigs that received ECMO or didn't receive any treatment didn't show this kind of movement. And the authors have no idea why this movement was happening. They don't think that it's because the brains were active again because they had brain scans that showed that there was no electrical activity, but they don't rule out that possibility. Or it's possible that the movement arose in the spinal cord, which can control some motor function independent of the brain.
Interviewer: Nick Petrić Howe
Well, this is certainly an intriguing story that Nature, I'm sure, will be keeping an eye on. So, thank you very much for joining me, Max.
Interviewee: Max Kozlov
Thanks for having me.
Interviewer: Nick Petrić Howe
And listeners, to read more about this study, you can check out Max's news article. There'll be a link to that in the show notes, and we'll also link to the paper.
Host: Benjamin Thompson
And that’s all for this week. But as always, you can reach out to us on Twitter – we’re @NaturePodcast. Or you can send us an email to podcast@nature.com. I’m Benjamin Thompson.
Interviewer: Nick Petrić Howe
And I’m Nick Petrić Howe. Thanks for listening.