Science Friday - Predicting Gun Deaths, Bat Flight, New Organ. March 30, 2018, Part 2

Episode Date: March 30, 2018

According to CDC data, more than 13,000 people die from gun homicides every year—and most of them are people of color who live in urban areas. Many of them are children. But as scientists seek to understand the causes and solutions for gun deaths, can we also learn to predict them…and even intervene before they happen? One researcher may have the answer: social media analysis.  Friendly neighbors. Olympic divers. Little horses with wings. No matter what you call the commonly misunderstood bat, they’re far more than simple nocturnal blood-drinkers. Bats have an impressive repertoire of noteworthy abilities—from super echolocation to agile, muscular wings. It’s a subject that has both inspired and lured scientists, like Sharon Swartz, a biologist who researches bat flight at Brown University. In this segment, she discusses how she takes a close look at the aerodynamics and wing morphology of these creatures to pin down the evolutionary origins of bat flight. Scientists have discovered a new piece of human anatomy we never knew we had—a layer of connective tissue that exists all over the body. It sits below the skin’s surface, lining the digestive tract, the lungs, and even our blood vessels. Researchers say it could be the missing link the medical community needs to move forward in a number of areas of research, including cancer and autoimmune disease.     Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. Have you thought about your interstitium today? You never heard of it? Well, apparently it's a new organ. Scientists say we never knew we had, a layer of spongy connective tissue that exists all over the body, including below the skin surface, lining the digestive tract, the lungs, even our blood vessels.

And it could be the missing lengthy medical community needs to advance cancer and autoimmune disease research. So why has this so-called organ remain undiscovered until now? Here to share with us their discovery as well as their theories as to what exactly the interstitium has been doing all this time. Our Neil Thies, Professor of Pathology, NYU School of Medicine. Welcome to Science Friday. Thank you. And Rebecca Wells, Professor of Medicine and Bioengineering at University of Pennsylvania.

Dr. Wells, welcome to Science Friday. Hi, Ira. So, Neil, how did we miss this? Where has it been hiding all this time? Well, the gold standard for the microanatomy of the body is what we see under the microscope. And what's interesting about this space is it's a fluid-filled space that's supported by this collagen bundle network or lattice. And in living tissue, it's filled with fluid. But when you take out tissue from the body, the first thing that happens is the tissue drains out.

The spaces collapse, the collagen bundles layer on top of each other. So whenever we've seen this structure under the microscope for the last 150 years, it's always looked like this dense wall of collagen. And that's sort of been our understanding of normal. You can sometimes see faint little cracks in it. And as a pathologist, looking at clinical specimens all the time, my teachers taught me that that was artifact we had torn the tissue. But now looking at it, we realized, no, no, no, those are the remnants of the big spaces.

The artifact is actually the real thing. and what we thought was real, this dense wall of collagen, turns out to be the artifact. Wow. And Dr. Wells-Pain is a picture of what, are there cells in it? What's inside of it? What's it made of? So inside of it, the major structure are some bundles of collagen. So we knew there was collagen there, but we didn't quite appreciate that they were really bundles floating in fluid. There's also elastin, which is an elastic fiber, as you might guess. There are a large number of proteoglycans and glycosaminoglycans. Those are proteins that have very large sugar residues attached, and glycosaminoglycans are large chains of those sugar residues.

And there are also some cells that we don't understand at all. We know that in at least right after birth in a mouse model, there are cells that seem to be depositing all of that collagen, but we don't see that kind of cell in adult structures. and so we need to figure out what does one cell type become the other cell type? What is the meaning of those cells? Does it mean that we as adults have cells that in the past produced a lot of collagen and are now dormant? We just don't know the answer to any of those questions.

Dr. Thais, you said that these fluid-filled spaces could be linked to the lymphatic system. How give us that connection? Well, so when we were trying to figure out what this fluid-filled space was, our first guess was, could it be some weird form of blood vessels? but for a variety of reasons, that's not it, and they're not filled with blood. They are filled with protein-rich fluid, as Becky just described, so it looks like lymph. So we thought could they be lymphatics? But for a variety of reasons, we excluded that, too. Then we're left with the third space, and it's actually been called the third space.

In hospitals, people with lots of edema, let's say with renal disease or post-operation, they call it third spacing. So that word exists, and what they mean is, the interstitial space, which is not a new word, it's an old word. It's where the fluid is that isn't in the blood vessels, not in the lymphatics, and not within cells. It's all the extracellular fluid that's outside of all that. It's about 20% of the fluid volume. That's where the lymph for lymphatics comes from. I see. Yeah. And so could that be sort of like, like, I don't want to say, the underground waterway system to carry other things to other parts of the body, maybe

stem cells or maybe cancerous cells or things like that? That certainly is the question. And in the paper, we actually show that stem cells do that and some kinds of inflammatory cells move through this space into lymphatic. So we actually demonstrate that concretely. This is one of the interesting things. Tumor cells, tumor of the skin or of the digestive tract, for example, until it got to that dense connective tissue layer, which now we know is fluid,

they wouldn't metastasize spread to lymph nodes until they got to that layer. But it's sort of an unasked question. How is it that this dense connective tissue layer would facilitate spread? You'd think this wall would prevent it. Well, now we know it's a fluid-filled highway. And in the paper we show the tumor cells invading into this space, they go directly to the lymph nodes. Wow. So, Dr. Wells, what are the next questions you want answered about the interstition?

That's about 20 years worth. I think we have to develop a much better understanding of how this space connects to lymphatics and to lymph nodes, since it almost certainly does. I'm very interested in what the cells in this space are and how they might be related to fibrosis, which is the development of scar tissue after injury. And I also think it would be, I think we need to understand more about what this space is doing mechanically, how it, is it acting as a shock absorber for all these organs in the body, and really what does it mean to have fluid flowing through it? So those are my three big questions. Let me go to a quick call from Robin Cleveland.

Hi, welcome to Science Friday. Hi, my name is Rob Truax. I'm a physician, an osteopathic physician, and this has been a very interesting phenomenon, and I'm a professor at the Ohio University Heritage College of Osceopathic Medicine, and this article that's published has actually been spread through, to our department because as DO's osteopaths, we've had literature for over 100 years

about the values of lymphatics and the fascia in its use in health and disease and the use of osteopathic manipulation to address fascia in its relationship with lymphatics. So I, now I don't know how the, your scientist there and the researchers consider the idea of fire in relationship to their interstitium.

Okay, let me get talking about. What do you think, Neil? That's one of the layers that's turned out to be this space, is the fascia. So traditionally, histologically, we say it's dense connective tissue, and yet the osteopathics world, as he said, knows that, no, there seems to be some sort of fluid relationship between them and the lymphatics. So one of my hopes, actually, when this paper came out, was that, that his community would see it and go,

ah, okay, now we have an anatomy for the stuff we've been talking about physiologically. Fascinating here, I think. Sorry. Dr. Wells, is there, you know, we talk about it being so pervasive, profusing the body, is there a brain barrier to it? Does it also get into the brain?

We also know about the blood brain barrier. Is there an interstitium brain battery, or is it up there also? You know, I don't know. I'm going to punt that one to Neil, who's the pathologist? And as a pathologist, I'm sort of scared of brain, but I asked our brain pathologists, neuropathologists, about this.

And they came running to me with some tissue from the spine from an operation yesterday, and we saw it. But the details of that I have no clue about it. I mean, that's another area that someone needs to investigate. Wow, you think that'd be huge, huge area. Yes. But doesn't it certainly surprises me. I'm not very smart, but I've been reading and writing about this stuff for 40 years to find out there's something new that we don't even know the most basic stuff about?

I mean, even speaking specifically about the brain and the interstitious human. Someone asked me in an interview this week, what else I thought was out there to discover. And I was like, well, if we knew, we would have discovered it already. There's always more. Every time you develop a new technique, a new perspective, a new way. of investigating something, you'll find stuff you missed that wasn't caught by the prior things. The only thing that happened here is we were collaborating with some guys who had a microscope that could look in human tissue at the microscopic level while it was alive.

So you could see it in action instead of a dried-out slide someplace. Exactly. And that made all the difference. And it couldn't have happened with any one of us. It had to be the team because we all brought different perspectives that could make sense Serendipity. And openness to working with other people across boundaries. Dr. Wells, you confirmed the tissue network was made up of collagen. What does collagen do and what role could it be serving here then? Also, in the body, collagen is the major structural protein.

Collagen is really what holds you together to a large extent. And so it's providing structure to the skin, to the bile ducts, to the GI tract, etc. what it's doing specifically, sort of at a, if we drill down a little bit, I think it certainly could serve as a highway for cells to travel along in metastasis, cancer metastasis, it may well be doing that. The cells of this space are adherent to collagen, and that may be very important to their function. We don't know that, but I think that that's possible.

Does this discovery lend any sort of mechanism for acupuncture? or acupressure working, you know, an explanation for it? Because I've heard this on the news all week. I would say both Neil and I are actually quite tickled by that. I think it does suggest that there may be a very clear anatomical mechanism for the way acupuncture works and for the fact that acupuncture does work, which I think has been very well shown. And understanding some of the chemical properties of college,

may help us understand acupuncture even further, knowing that this space is filled with collagen bundles. But that's something that we're investigating right now. And there's work from like 10 years ago, a fellow Edward Yang, who I was in touch with, who showed that they're using MRI machines to measure sound waves and tissue. That sound waves, if you put a needle in the skin randomly, it goes a centimeter in all directions. But if you put it on an acupoint, it travels all the way up the meridian. And we talked on the phone. This was 10, 15 years ago, about where could that fluid wave?

What cells was it passing through? We never thought there was actually a fluid channel. So now it raises the question, are these collagen bundles arrayed in such a way that they dampen fluid movement off of the meridian? And maybe the meridian corresponds to a channel created by these structures. We can now have hypotheses about this stuff that we couldn't make before. And you can actually pointedly study stuff. Yes. Because you didn't know it existed before you couldn't.

Correct, yeah. Tell them about electricity, Becky. Got 30 seconds, Becky, quick. No, no, no. I mean, it was what I said before. Tell us about that. If you've been, Becky found this out. Go ahead, quick.

No, I think that, you know, collagen has some interesting electrical properties, and knowing that there are these big collagen bundles that run through this space, if collagen has certain electric, if it has these certain electrical properties, it does make you wonder how, um, you how signals might be transmitted across the college. We'll be back to both of you, Rebecca Wells, Neil Thies. Thank you both for taking time to be with us today. Thank you. We're going to take a short break while you chew on that,

and we'll be right back after this. Stay with us. This is Science Friday. I'm Ira Flato. Last week, we explored some of the gaps in gun research as teenagers around the nation gravitated to Washington for the March for our lives. But as one of our guests pointed out last week,

While more than 30,000 people die per year from gun injuries, that story plays out differently, depending on whom you are and where you live. More than 80% of white people who die from gun injuries are suicide victims. More than 80% of black people who die from gun injuries are the victims of homicides. This week, research that focuses on the homicides, and that's what we're going to be talking about, not just mass shootings like the one in Parkland, Florida, that led to this recent wave of youth activism, but homicide and urban. and that's what we're going to be talking about, not just mass shootings like the one in Parkland, Florida, that led to this recent wave of youth activism, but homicide in urban centers like Chicago and Baltimore and Philadelphia and beyond

where more than 80% of gun homicides occur. If gun violence is a public health issue, is there a public health intervention, like a vaccine for homicide? Or at the very least, can we predict it using social media, when and where the next homicide will be? One of my next guests has research out this week in the journal Digital Medicine that says that, yes, social media could point the way. When young people in Chicago who are affiliated with gangs lose a loved one to gun violence, their first tweets are about grief, but that grief turns to aggression and further violence within two days.

Study author Desmond Patton uses machine learning algorithms to detect and categorize these conversations. and other research is demonstrating the degree to which homicide is contagious. If you know a gunshot wound victim, you have a higher chance of becoming one yourself. Gun violence is contagious like other public health problems. That's how this theory goes. Here to explain their work of what may come of it are my guest, Desmond Patton, assistant professor in the School of Social Work at Columbia University, author of the social media study. Welcome to Science Friday.

Thank you so much for having me. Andrew Papa Christos is professor of sociology at Northwestern University who studies how networks can transmit gun violence. Welcome to Science Friday. Thanks. Glad to be here. You're welcome. Desmond, as I just said, gun violence in the urban areas kills more than 13,000 people per year. About a third of the total number of killed by guns in a year. What drew you, what drew each of you to try to bring the data to solving this problem? Desmond, let's ask you first. Sure. So I did my PhD at the University of Chicago, and I spent about a year with young black men who were high achieving. They were doing really well in school, but I wanted to understand how they were staying connected to school while also navigating violence in their community. And what became very clear during that ethnographic study is that they were cognitively geocoding their neighborhood, trying to make sense of all of the people and things and spaces and places that they had to navigate and understand very well. well in order to stay safe. And this also becomes an apparatus, if you will, that they use when they're engaging in their digital life as well. And so they need to remain connected to the community. And so they also are mapping individuals and mapping conversations to stay safe as well. So you think that the social media is a fertile ground to be studied about

gun violence? So I look at social media as an environmental context so that we can understand the pathways to violence. And in my research, I've learned that young people are initially using social media to communicate with one another, to share news, and to talk about the throes of their everyday life. And when that experience is wrapped into an ecology of violence and hyper exposure to violence, the conversations that they talk about also include their exposure to violence. And it sets out flags that you might follow. Absolutely. But I want to be clear that I think it's, It's also important to not just focus on threats and aggressive communication on social media

because that may lead you down a trope as well. I think what I've learned is that there is a pathway and that oftentimes expressions of grief and trauma and pain and experiences with loved ones are the things that people initially come to social media to discuss. Yeah, because sometimes, as you point out, I've seen your TED talk on this, is that sometimes we focus too much on just the violent aspect of it. Andrew, Papa Chrysos, what brought you to this line of work? So, I think, much like Desmond, I was born and raised and educated in Chicago in the 80s and 90s,

and you couldn't escape the dialogue around gun violence and gun homicide in particular. And as my sort of work developed, I kept coming back to what is it that's driving violence, what's keeping it at high levels in some neighborhoods rather than other neighborhoods, and more importantly, what can be done by it. And as you suggested at the beginning, one of the things that gun, homicide does in this country is it drives massive disparities in health, mental health, and just mortality outcomes, especially among black and white young men. And so you could be in one part of Chicago, and if you're white, you're a chance that you'll live seven or eight or ten years longer,

and we know this sort of at birth. And so the idea, as I started getting into the research in this area, was really trying to unpack ways to understand this epidemic beyond the sort of political framing of gun violence epidemic, because it is an epidemic. And if it's an epidemic, it should follow certain rules. It should be transmitted in certain ways. It should be concentrated in certain ways. And so the work was really trying to sort of leverage that sort of information to figure out and think about ways we can stop these sort of cascades of gun violence. So you can, as an epidemics, as in diseases, you can put a number about how it's spreading.

Can you do that also for gun violence? I think that that's what my research really is focusing on. So one of the things that the sort of network-based approach uses, and I'm talking about sort of human social networks, not just social media networks, but who you're related to who you engage in certain behaviors with, one of the things that shows is that gun violence victimization is even more socially concentrated than just spatially concentrated, meaning that most gun violence acts are happening in very small networks, even within, say, high crime communities. And the science is suggesting that, in fact, it is transmitted, which is if I get shot, if you're one of my associates,

your likelihood of getting shot just skyrockets within the time period around that shooting. And then subsequently, your friend's friend and your friend's friend, and it literally builds out like a cascade over time. But is there an intervention someplace? You know, with a disease, you try to quarantine people or you try to stop it with it? vaccine or treatment? Is there an intervention period in your disease that you're studying? So I think there are lots of points of intervention. Of course, the best one is the biggest one, which is growing up in a community that is safe and healthy, you know, full stop. That's one of the biggest sort of vaccinations to use your phrase. But there are sort of emergency responses,

which is can you stop these cascades? And while lots of interventions are not using these sorts of analytics formally, good preachers, teachers, teachers, cops, social workers, educators, they live in these networks. And what we see is interventions, whether they're public health or otherwise, that can focus efforts on sort of small populations, small geographic areas or sort of insert themselves in these networks with, say, trauma care or violence interruption. You can see fairly significant short-term reductions in gun violence, which is they can slow things down, save a life.

But what they don't do is they don't do the big things. because they don't fix communities or schools. And you have to kind of do both at the same time. It's not one or the other. Desmond, your work looks at how, as you say, youth in Chicago talk to each other on Twitter and teaching machine learning to follow. How hard is it to teach a machine? It is extremely hard.

And so I've had the good pleasure of working with the Data Science Institute at Columbia University, and I partnered with Kathy McEwen, who was one of the leading data scientists in our country. and we have thrown the gold standard data science techniques at this problem. And the issue is it doesn't understand the complexity, the nuance and culture that's embedded in the twin of communication that I look at. And so to circumvent that, we had to develop our own ontologies and more importantly involved community in the translation and interpretation of social media communication. So that means we hire young people from Chicago to translate and interpret the data

and to also validate our own judgments or tagging of the data, if you will. How good is Twitter actually understanding the personalities involved? I think what's important to know about Twitter is that young people bring the understanding of their world, of their experiences to Twitter, and it's really coming up on us to try to understand it the best way we can. And so what we do is we go through a set of procedures to really extract context in our analysis of, Twitter data, and then we talk to community members to validate our interpretations so as to not misinterpret a rap lyric for a threat, if you will. What kind of would be a typical tweet that you would be looking at?

So we look at the gamut of tweets, and so we look at communication around love and happiness and joy, and look at a lot of pain and trauma as well. We'll be come across a lot of rap lyrics and threats and taunts, but also, pain and responses to trauma as well. And, Andrew, what happens once we can predict an individual person's risk? What do we actually do? What can we do about it? What should we? Well, I think one of the things that's important as you try to understand people's exposure to risk and their level of risk is, in fact, we have lots of things that work already around

trauma reduction, around violence reduction, around promoting mobility. So part of, I think, one of the benefits of these sorts of approaches is getting the right resources to the right people in a timely fashion, which also requires a lot of political maneuvering, which is getting people to share information, share responsibility, and being able to mobilize them quickly. And also, to Desmond's point, you know, to be able to have some human intelligence and human thought going behind something and not just looking at a printout of numbers or scores, but be able to say, hey, that's a rap lyric. That's not something Andrew said, or that was something that happened 20 years ago, not something that happened 20 minutes ago. So it's really important to just move beyond sort of individual numbers and figures, but have it in that sort of iterative human context as well.

Desmond, is there a role for law enforcement in any interventions to prevent gun violence, or does the science suggest? Well, I think that law enforcement has already been involved, particularly in the east of social media's evidence. for understanding future criminal behavior. I think a part of the challenge is how do we develop more contextually driven techniques to make sure that when we're looking at text and looking at images that we are embedded in understanding that is local and that is as accurate as possible. And so I think that it's really important to engage in interdisciplinary collaboration, to push each other to make sure that we're not over-policing these communities.

Right. That brings me to this question. Last week we focused on some of the difficulties public health researchers having getting data to study gun violence. To that end, what's on your data wish list? What would you study, if I give you a blank check and you could study? What do you need to know? I mean, I would love to be able to look at all social media platforms. Some of the, when I talk to youth about the platforms that they are engaged in, one of them is Snapchat, but it's really hard to get data from Snapchat because, well, A, the videos have been very quick, and so it's very hard to capture those videos in a kind of real rigorous way.

And so I think trying to tap into the variety of platforms would be very helpful in triangulating our approach to analysis. Andrew, what would you like to have? Well, on the data question, I could just send you a bunch of unfunded proposals we can talk about. Don't send it to me. So, I mean, I think the first barrier, the first thing I'd love to do would be to link data sets across different systems. So by default, I think criminal justice data is often, you know, the best kept data, but to be able to link individuals across, say, educational, public health and health care

and criminal justice systems, that would be the first step. And some cities like Chicago have great data infrastructures and others just don't. The second thing I would add, which is part of the current public dialogue, is, of course, I would love to have information on the guns used in crimes, which most often are illegally funneled guns. They're not sort of the guns that are used legally in Chicago, which is always on this national stage here. One of the second sources of guns is, of course, Indiana, where you can literally walk across the street and be in a different state and under different laws. So the ability to look and see how illegal firearms move within networks and markets, that would really go a long way for intervention and prevention purposes.

That's what we were talking about last week. This is Science Friday from PRI, Public Radio International. Talking about gun violence with Desmond Patton, Andrew Pappacristos, despite the students from Parkland, Florida, the ones organizing the Never Again movement, making a specific point about urban homicides in some of their interviews, it feels like we're not hearing as much about this in the conversation. We're not hearing a lot about urban gun violence in this conversation coming from teenagers.

I mean, I think why they're so powerful about these kids from Parkland is that they are speaking out and they're being listened to. And certainly as much as we, you know, care about these mass shootings, is an urban homicide from these kids is not getting much attention. Do we, is there a way for these kids to take, you know, to see the power that the Parkland kids are getting? and them speaking out more? Well, I think what's been interesting about this whole scenario is that the Parkland students have been engaged in conversations with youth from the south side of Chicago. And a part of the challenge is we recognize that mass shootings are a societal crisis, but we're not, when we talk about violence that happens in poor communities and my own youth of color, we're not equating the same conversations or resources behind it. And I think people get really...

They're not getting the same. stage? Absolutely not. They're not getting the same megaphone. Right. It's a very important this year. Would you believe, agree Andrew? What to do about that? So I would give a wholehearted amen to that. And I actually

think, for those of us have been doing this research for a long time, you know, we had the same reaction after Sandy Hook, which is you have, you know, literally dead white suburban school kids that started a movement and yet we've made very little progress since then. And so I think making sure that both

of these things are happening and on the national dialogue at the same time is essential. And like Desmond, I actually want to applaud the student organizers who have gone far to include those voices in many of the marches. I know here in Connecticut, we went to the Hartford March and they shared the stage, which is great. And I think that everyone should make a conscious effort to keep all these sorts of gun violence, including suicide, sort of on the national stage. And to go to your research point, by the way, they're different types of guns, they're different types of populations, and they're all tragic, and many of them are actually, in fact, preventable. Do you think that people are listening any more now than before?

Desmond, you're sort of looking at me like, I'm crazy. You know, I attended the march here in New York City, and I was really pleased to see so many people and so many different types of people. I was also wondering where have they been, and I also had. I also notice a lot of people very happy and showing a lot of posters and me very excited. And I felt very solemn in the moment because I know too many people that have been shot. This isn't something that's very abstract for me. This is deadly serious.

I think people are listening. The impact of that listening is, I think we have some time to see what happens from that. I would just add to it to build on that momentum, we know we're going to fail if we don't make any changes, right? For either these sorts of types of violence we're talking about, we need to really keep it going and lead to change, which actually, it happened in some states after Sandy Hook and some of the other shootings. But, you know, we're at a moment, but what's going to happen? And I think it's up to a lot of us to keep the sort of the dialogue going and make a lot of it, at least data informed. I'm glad we had some part in that dialogue. Desmond Patton, this is Professor of School of Social Work at Columbia, Andrew Papa Christos, Professor of Sociology at Northwestern University.

Thank you both for taking time. to be with us today. The pleasure. You're welcome. After the break, what these flying mammals can do will drive you batty. Get it?

Yes, they are bats. They fly like maniacs, and they can hear better than we can see. The engineering secrets of our furry friends coming up after this break, so stay with us. We'll be right back. This is Science Friday.

I'm Ira Flato. Birds and bats. One's a dinosaur, the other's a mammal. One's feather. The other is fuzzy. But both have a lot. have evolved convergently to lift into the air when they flap their front limbs.

Flight, the ability that we take for granted every time we board an airplane now. But it seems like bats are just doing the same thing that birds do. Well, you might be surprised to hear that you're wrong. Bats turns out have a number of sophisticated aerodynamic tricks up their sleeves, from tiny muscles that selectively stiffen to a figure skater move for flipping onto cave ceiling. Wow, we have all of these tricks captured on high-speed cameras. They're the subject of our newest video on the macroscope. Up on our webpage at Science Friday.com slash bat wings.

It really, really is an incredible sight to see what all these bats are doing. Here to help us celebrate the beautiful mechanics of bat flight is Sharon Swartz, Professor of Ecology, Evolutionary, Biology, and Engineering at Brown University. Welcome to Science Friday. Hi, Ira. I am thrilled to be here to talk to you and your audience today. Would you believe I've even more thrilled to talk to you. I would not believe that.

Well, you should. You should because I'm usually the dumbest person in the room. Let's talk about the birds flap their forelimbs, bats flap their forelims. How could their flight be that different? It's amazing how different they are. Although I have to say when I started into this field some very large number of years ago now, people told me that bird flight, bath flight, basically the same thing, just a little minor variation on a theme.

But it's not really true. And the more we understand about bat flight, the more we understand how different these two ways of getting around the skies really are. Your research partner, Kenny Breyer, who also featured in our macroscope video, describes one of the most impressive tricks of bats landing. They have to slow down, they have to flip themselves upside down, and land hanging onto the ceiling or hanging onto a tree roost. It's like doing a high dive backwards.

Well, bats have a problem that birds don't have. When you have a wing in the air, the amount of lift that that wing makes is a function of how fast it's going. So as the animal slows down, it generates less lift. And if you want to land on the ground, that's a good thing. You slow down, you move downward. You're a bird. You're all set. But bats don't land on the ground.

So as they slow down, they need to move upward. and that really is a problem when it comes to physics. So it's sort of like we see in ice skating. They do those little flips and things. They're moving their center of gravities and they're moving their momentum around just to get positioned so they can grab the ceiling. It turns out that that's exactly what they do, but I don't think it was obvious, certainly not to us,

before we started this research, that that's what a bat needs to do to carry out a landing. But actually as a bat approaches the site that it's going to, on which it's going to make its landing, really what happens is that the aerodynamics barely function at all. And the fact that a bat has pretty big wings that are actually kind of heavy for a flying animal lets it act just like one of those Olympic skaters. And as the wings move, and what's really a pretty highly programmed,

very precisely maneuvered set of motions, those wing movements can get the body to exactly where the bat wanted to go, even though it's slowing down and it's not getting any lift from those wings anymore. It's amazing. And because no conversation about bats is complete, without a look at their amazing echolocating ability, we're also joined by Cynthia Moss, Professor of Neuroscience, director of the Bat Lab at Johns Hopkins University. Welcome to Science Friday. Oh, thank you. It's a great pleasure to be here. Let's talk about it. You study the neuroscience of a bat's echolocation sensing. Does a bat need a specialized brain

to process the signals from echolocation? Well, bats produce very high-frequency sounds, which return echoes from objects in the environment, and the very high-frequency sounds they use for echolocation require very high-frequency hearing. And there appear to be some special circuits in the bat brain that help process the information to build pictures, if you will,

of objects in the world through sound. So does it really have to do, you know, computers we speak about how quickly they can process information. Is that true of a bat's brain? Well, bats have to process information very rapidly. Imagine they're flying, as Sharon Schwartz is described, and the world is continuously changing as they're moving through that world. And the echolocation sounds they produce are very short packets, carry packets of information. And so from one echo to the next, the world has changed, which will. really requires very rapid processing.

So how many seconds, or microseconds, pico, whatever, how do you measure that? Well, there have been some experiments that measure the bat's ability to measure time delays between calls and echoes, which is the bat's cue for distance measurement. So sound travels in air. It has to go from the bat to an object and then back again. And there's about six milliseconds of echo delay for each meter of object. distance. And experiments have been conducted to test the bat's ability to discriminate small differences in distance, and they can discriminate in the microsecond range. Really astonishing.

Wow, that is, in fact, we have some audio of a bat's echolocation chirps slowed down by a factor of 16. That's amazing. What caused the change in speed right there? Yeah, so what we're listening to are calls produced by the big brown bat, the local species, and it's going after insect prey. And so the sound frequencies it's using are well above our range of hearing, but for each flowing of the playback speed, you decrease the frequency. So you're actually listening to the real signals, but shifted into the range we can hear.

And as a bat approaches an insect, it increases the rate at which it's producing calls. So you could hear at first they're producing calls, or this individual is producing calls at a rate of maybe 10 to 20 per second, and at the very end, about 150 sounds per second. Wow. Sharon, if you look at the video or at ScienceFriday.com slash bat wings, our macroscopic, the macroscope video, you see the slow motion movement of those wings. How are they able to so delicately?

You know, it's almost like a ballet going on there. It is. Absolutely. You know, I'd say that they're able to do that partly because they're mammals, and they have, they're basically using the same musculoskeletal system that we have that's been fine-tuned over evolutionary time to carry out the specific tasks that they need for their ecological environment, the environment of flight. They're a lot smaller than us lumbering humans. and in general, animals have a locomotor cycle frequency that relates to their body size. So if we were to watch the movements of any very small animal, even if we watched the limb movements of a mouse slowed down, it would look very impressive and elegant to us, too, in slow motion.

But the bearings must have specialized muscles in there or something to make them do what they do so precisely. Well, so part of what makes a bat wing so finely tuned to the tasks at hand are the distinctive structures of the wing. So one of those is the highly specialized skin. So birds have very effective skin, but nothing like the unique skin of bats. So in bats, the skin is extremely thin. It's only a few percent of a millimeter in thickness. It still has epidermis, just like other mammalian skin has. But there's also a special group of muscles that invest the skin of the wing membrane in bats.

Those muscles are just like the muscles of our limbs. If we look at the tissue itself, it doesn't look very different. But unlike our limb muscles, those muscles don't attach to bones. They only attach within the skin itself. And the muscles within the skin give the bat the capacity to really control the skin in a way that we don't normally see in skin. So the bat has a system for actively changing how stiff the wing membrane can be. So during flight, the bat can turn those muscles on and off with every wing beat cycle. so even though those animals might be flapping their wings 10 or 15 times every second,

they can use the muscles that are sitting inside the skin to change the stiffness of the skin many times per second. Cynthia, we heard some of the chirps from the echolocation. Are there different kinds of signals, frequencies, chirps that they, do you have a smorgasbore that the bat can choose from when it needs to? Well, individual species of bats vary their echolocation sounds as they perform different tasks as they approach objects. But there are also over 1,000 different species of bats that use echolocation. And so there's a wide range of different kinds of signals that different bat species use.

Some more tonal signals, some modulated in frequency, and some even use clicks produced by the tongue. And how high frequency are they, the highest frequencies? Oh, the highest frequencies that some bat species use exceed 200 kilohertz. Our upper limit of hearing is 20 kilohertz, and that's only if we have very good high frequency hearing. So way, way above ours. And I know from studying a little bit about sound, the higher the frequency, the shorter, the wavelength, the finer the detail you can pick down. So these very high frequency sounds are really well designed to bounce off of small objects like, little mosquitoes.

That's quite interesting. Sharon, let's talk. Yes, go ahead. I want to say here, well, it's really interesting to note. So Cindy pointed out that there's over a thousand species of bats that use ultrasonic echolocation cause that they emit from their larynx. But there's also a small number of bats, a couple hundred species, that don't use ultrasonic echolocation that are primarily visual in their navigation of the.

aerial world. And we've known for a long time that one group, one genus of those bats use their tongues to make clicking sounds, and they listen to the echoes of their tongue clicks. It's not quite the same as the sophisticated ultrasonic echolocation that Cindy's been talking about. And recently, some researchers led by Yossi Yovale at Tel Aviv University have found that those bats and some other non-echo-quote non-echolocating bats also emit sounds with their wings. So when they're flying, the sounds that are made by their wings during flight emit enough sound that the bats listen to the echoes of the wing sounds and are able to use these wing flap sound echoes as part of their navigation system as well.

And Sharon, isn't it wing clapping? It seems to be something about when the wings come together. So I think that there's a lot of mysteries about this wing sound production. So I would say that there are many open questions about the wing sound production that we have to solve. I would like talking about them here on Science Friday from PRI Public Radio International. Talking about how fascinating that bats are. I mean, Cynthia Moss and Sharon Schwartz. It's almost insulting to call them flying rats, I would think, to bat specialists.

Well, they're not. Bats do not belong to the same group of animals as rodents. There you go. It's been a long time since people thought that bats might be closely related to rodents. So, yes, they have that name in German, but bats are not closely related to. Well, let's talk about the relationship. Let's talk about evolution. The theories about bird flight evolution includes a gliding ancestor that learned to flap out actively.

And then you had a ground-up running ancestor that starts to generate lift. So what are the theories about bat flight? What's the evolution behind that? Well, so I think that the most commonly held ideas about how bats evolved the capacity to fly, see bats as coming from a gliding ancestor. There's several reasons people think that, and one is that gliding seems to be a form of specialized movement that evolves very easily within mammals. If there's any such thing as something evolving easily.

So specialized gliding wings, so not the flapping wings that we see in bats, but the kind of wings that you'd see in a flying squirrel like rocky, from walking in Bullwinkle, that kind of gliding wing has evolved at least eight times independently in mammalian evolution, a couple times independently in rodents, and three times in marsupials, and once in the specialized group of mammals that we find in the Indo-Pacific that are called flying lemurs, we don't know why they're called flying lemurs, because they don't really fly, and they aren't really lemurs, but it seems like a good name at the time. So gliding evolves over and over in mammalian evolutionary history.

And these gliding wings often share a number of characteristics. They are made of skin in very much the same way that bat wings are made of skin. And they have certain patterns of muscles in the wing that are similar to the muscles in the skin of bat wings and certain patterns of innervation that are distinctive that we also see in. bat wings. And they all incorporate the forelim and the hind limb, just like bat wings. And this pattern makes us think that it's very likely that they're, even though we don't have a fossil record for a gliding ancestor for bats, it's very likely that there could have been one, just that we don't yet have direct evidence for it. One last question about the bats, the things that they

stalk. I have a tweet from Wallace who says, does the echolocation stun the insects? And it Can the insects engineer a way over evolution to try to avoid being eaten by the bats? Well, I don't think there's any evidence that bats stun insects, but many different insect species have evolved strategies to avoid being eaten by bats. There are some insects that make very high-frequency clicks that interfere with the bats' echolocation behavior. And so that's one example of a strategy to avoid being eaten. There you go. We've run out of time.

So fascinating about these bats. Cynthia Moths, Professor of Neuroscience and Director at the Bat Lab at Johns Hopkins University, Sharon Schwartz, Professor of Ecology, Evolutionary Biology, and Engineering at Brown University. Thank you both for taking time to be with us today. Oh, thank you. Thank you, Ira. We'll have to have you back. And you can see the latest macroscope video on our website.

This is a great video. If you want to see bats flying in slow motion and what they can do, ScienceFriiday.com slash batwing. ScienceFriety.com slash. bat wings. B.J. Liederman composed our theme music, and if you missed any part of the program, subscribe to our podcast. If you have a smart speaker, you can ask it to play Science Friday, whatever you want. So, you know, every day now is Science Friday. So have a great weekend. Happy holidays if you're celebrating. I'm Ira Flato in New York.