Science Friday - Immunotherapy, The Evolution Of Eyebrows, Unconventional Bird Calls. April 13, 2018, Part 2

Episode Date: April 13, 2018

Tumors are masters of disguise. The field of immunotherapy—teaching our immune system to recognize cancer—is burgeoning with solutions to this problem.  The eyes may be the window to the soul, but it’s our eyebrows that are doing all the talking. The ability to wiggle those two hairy features around isn’t just some party trick, it’s almost like a secret language—one that even our ancient ancestors used to their advantage.  One of the first signs of spring are the sounds of birds chirping in search of food, nesting grounds, and a potential mate. But sometimes those bird calls aren’t coming from the source you’d expect. In some species, female birds also use calls, and a group of hummingbirds creates calls with their tail feathers.  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. The eyes may be the window into the soul, but you might argue that it's our eyebrows that are doing all the talking. Let me tell you what I mean. Like, if you see someone you recognize, you give them the eyebrow flash, you want to convey sympathy or concern, a furrowed brow is best for that. And nothing says, I'm skeptical of you like a single arched eyebrow. Yes, the ability to wiggle those two hairy high, isn't just some party trick. It's almost like a secret language, one that even our ancient ancestors used to their advantage. Some people make a living out of studying arching eyebrows.

Penny Spikens is one of them. Dr. Spikens is a senior lecturer in the Archaeology of Human Origin at the University of York. Dr. Spikens, welcome to the show. Hello. So what did our ancient ancestors' eyebrows look like? Well, actually the story about eyebrows goes back a little bit before people had eyebrows like our own because if you go back like 200,000 years ago and you see some early human, actually their face looks really different from ours

because they had huge brow ridges, a big bony protrusion that went above their eye. And for a long time, we've not known what that's for. So we've really not understood what's happening in people's eyes that far back in time. There's been an idea it's to do with maybe buttressing the face or supporting chewing muscles, all of those things. So what we did in our research, Ricardo Godineo, one of the researchers here, made a model of the carbway skull, that's an archaic human, with these huge superorbital ridges and tried to test out what it could be for. And what was really interesting was that there was no good functional explanation. It doesn't help with chewing. If you had that there or you didn't have that there made no difference to the way in which your face was working, really,

in which those muscles in the jaw was working. That was really interesting because that suggested that this bony ridge had a kind of social function. And of course, if we look at other primates, we can see similar bony ridges. You imagine chimpanzee, you know, you can see chimpanzees have got a bony ridge. And in fact, some primates like mandrels have a huge bony extension down their nose. And in these primates, these are kind of gestures of intimidation. You know, these are big scary things permanently there. Paula Higgins in our groups compare them to antlers.

You know, there's something to do with social competition that are just permanently there above the eyes. But of course, this big lump, the effect of having this big lump and a receding forehead is that there's not that much movement can be made above your eyes. this is making a pretty obvious signal. It's a blunt signal to others. We know chimps can pull their skin over the lump above their eyes, but it's a yes or no kind of like signal. So as we go through time, as we get towards our own species,

this bony lump disappears, and instead we have vertical foreheads, we don't have a brow ridge, and we have eyebrows that move around. And that's interesting, because from being species that can't make much subtle, signs above our eyes, we become species that can make all these subtle signs. As you were saying, sympathy, a gesture of recognition, one raised eyebrow, although I have to say,

one of the disappointing things of that is I can't raise one of my eyebrows. Well, I was going to ask you about that. Does that mean that if you can do that, you have an advantage over, in expression-wise, over someone who cannot? I don't know. I think I can gesture a little bit of questioning by raising both eyebrows pretty well. so I think I've probably got that kind of, I get the same thing across, even though I can't quite do it with one eyebrow.

So I don't think we can really apply it between us. The difference is us as modern humans compared to the species in the past. And the interesting thing that tells us, I think, about changing pressures on what was important about social relationships. Try to kind of, you know, what we do with our eyebrows is a lot to do with friendly things, friendly gestures, really subtle friendly gestures. You know, and really subtle social justice. Like you said about raising your eyebrows. You know, I was saying, you know, you sit in a meeting and you say something and you think you're on the right track.

And then you notice that a few people have raised their eyebrows and you think, okay, maybe I'll draw that back in a little bit. It's so subtle, isn't it? It is. But why did we get two eyebrows and not one mono brow that goes across? I don't think we know about that. We only know about what makes eyebrows movable. You know, it's about the muscle movements allowing them to. move, you know? In fact, some people do have one eyebrow that goes across, don't they? But I think

that's all just part of, like, the glorious thing about the differences between us. Yeah. Why do you think eyebrows got to be the most expressive feature? Why not cheekbones or jutting jaws? There's something important about that space above the eye? I guess you're saying it's because that's where the bony part was and that's what people noticed first. I guess. I mean, our eyes are very expressive. All the movements around our eyes are expressive. But it's just that bit above the eye is changing through time. And that's why we're really interested. in it. But can I tell you something about dogs? I think you're going to find this interesting.

You talked about puppies and maggots a while before, but this is something completely different. Okay, so when dogs became domesticated, they also had changes in their face, but the other thing that happened is they got more waggy tails. And in a way, that's quite similar, because they found a means, you know, evolutionarily, there was a means of showing friendliness at a distance

to other dogs, to humans, because your tail's really waggy. Now, we don't have tails. We couldn't have waggy. But we could have these subtle signals in eyebrows that say, hey, I'm not scary. You know, I don't have a big brow ridge. I'm not trying to be intimidating. I'm not going for social dominance. I wouldn't be friends.

So when did it smiling then become important as a signal cue to people? Do you think eyebrow is more important than a smile? I don't know. And these are wonderful, wonderful questions which we should think about. But it's very hard to say. I mean, we can look in our research because we have a brow ridge that we can. measure and we can model, you know, and we have a lack of a browage, but it's very hard to get at those kind of smiling muscles, because you could have them but not use them, you know?

Yeah. So if you have some sort of interference with the muscles in your forehead that you're not able to move your eyebrows as well as someone else, you're not conveying messages as easily. Oh, that's so interesting too. You know, there's been some studies on people who had Botox on their forehead. They're not making the messages, but what's more interesting still is they're less empathetic to other people because without being able to make those little messages imagine sympathy you don't really feel the same uh yourself in response to somebody else's feelings so you're actually feeling less empathy towards someone else which is really interesting because that's just with numbing those muscles in the forehead so so our eyebrows then vestiges

of our ancient ancestors that we learned how to make better use of we don't know whether on top of the bony ridges that would have existed prior to our species, there could have been bits of fluff. We can't tell there's nothing preserved. But of course, if we look at other primates, they certainly don't have that. You know, the brow ridge, you know, is actually bare. So it's much more likely. I mean, if I had a bed on it, I'd say they didn't have eyebrows. But unless we actually find somebody completely preserved, that shows us we didn't, we can never say for sure. But most plausibly, they didn't have eyebrows. And once the face shape changed, then those eyebrows came in and the movability of the eyebrows came in.

I got you. So why did we develop these modern face shapes, the modern foreheads? Well, the question about, there were several things going on. Okay. So one of the things going on is changes, all sorts of hormones, changes in our hormones that we think are to do with the need to get on better with others. So we see a flattening of the face. There's some changes to do with perhaps chewing different foods as well. But if we look at the wider social picture, what's really interesting is that only after faces have changed, and we've got these eyebrows,

do we see connections between different groups? And they're really important for human evolution, because we see gifts moving along long distances, people move into new territories, and we see different group compositions. Yeah. Yeah. Now, if eyebrows are such an important tool for social communications,

why do we pluck them out? Again, now, you know, this is what got Paul, one of the people who were working on the project, started on this, because he was actually pondering his daughters plucking their eyebrows and thinking, what is this with eyebrows? Why are eyebrows so important?

And that's how we started to look at eyebrows. But as to why we pluck them out, that's just us, isn't it? Not humanity as a whole. I think we're probably a bit odd in time and space, aren't we, our societies for doing the eyebrow-plucking thing. So I don't know whether there's a good evolutionary explanation for that. We do a lot of odd stuff.

And plugging our eyebrows is probably just one of them. It's sort of a fashion thing. Yeah. Yeah. So what do you want to know more about eyebrows that you don't know? What kind of questions still remain? I think, you know, what interests me is that bigger picture about why and how humans become more tolerant of people that they don't know and able to forge relationships based on trust with people that maybe live a long way away,

that they don't meet very often, because that's a big change. If we look at the rest of primates, they don't have relationships with other groups, do they? They don't form relationships with other groups, and yet we all do that. So I'm interested on that, like, what exactly is happening around those changes of which eyebrows are just one part that allow us to kind of work with other people? So if I want to make a good impression on a stranger, should I use my eyebrows to do something? I guess it depends what you're thinking of doing with your eyebrows. Like, you know, a great big frown, I probably wouldn't recommend that. That might not go down so well.

Well, Groucho Marx made good use of his eyebrows. Yeah. Do you know who else made good use of his eyebrows? Have you seen Charles Darwin's eyebrows? Not recently. He has really impressive eyebrows. That's the answer to that question. No, no, they're not missing.

They're not missing. No, yeah, yeah. But if you look on the web under Charles, he had some pretty impressive eyebrows, which is interesting because he was one of the first people that noticed how important the eyebrows were in kind of facial expressions. Is that right? Yeah. Did he write about that? I mean, he's published.

He did. That was like 1872, expressions of emotion in man and animals. So that's the first big work that looks of expressions of emotions all that time ago, yeah. And you wonder if he looked in the mirror and thought, hmm, eyebrows. Well, there's some birds that have eyebrows. Really? Yeah, I've seen some birds with sort of big fluffy feathers up there that look sort of like eyebrows. There's a study on dogs in shelters, and some dogs can lift one.

It's not quite an eyebrow, but one area above their eye looks like an eyebrow. And they're the ones that are most likely to get rehomed because we think they look so cute. And there you have it. That's the secret of eyebrows looking cute and then communication. Thank you, Penny. Very interesting. Thank you, Ira. Thank you for taking time.

You're welcome. Penny Spikins is a senior lecturer in the Archaeology of Human Origin at the University of York. We're going to take a break. And when we come back, you know, we are learning more and more about. training the immune system to fight tumors, but not for every cancer or every patient. How can we expand the promise and power of immunotherapy? It's in the news a lot lately. It doesn't work most of the time, and a lot of people.

Why not? And there are some really interesting new ideas about how to motivate the body's immune system to get better at it. We'll talk about it after the break. This is Science Friday. I'm Ira Flato. Chemotherapy has been a standard practice for decades. it kills healthy cells as well as cancerous ones, it has many side effects. It's not becoming clear that our immune systems are one of the best weapons we have.

Our bodies come with an array of tools for removing unwelcome visitors, but tumors are also adept at telling our T cells and lymphocytes to move along. There's nothing to see here. So even as the field of immunotherapy advances, only a fraction of the patients respond, about 25% from melanoma, for example. And there can be an intense autoimmune backlash, where the immune system starts to attack the rest of the body and not just the cancer. So what if you could cure your cancer, but at the cost of diabetes? That's not a great idea.

Well, like in any war, the one against cancer is sort of a chess game, learning to outsmart, outthink, outmove your enemy. Now there is one approach. Try to activate more kinds of cells in the immune system to attack the tumor. Use more of the tools on that cellular Swiss Army knife. And new research published in science last month explores just that, using antibodies to bring our body's natural killer cells into the fray. Here to explain the approach and what lies ahead for cancer immunotherapy is Dr. Kai Wuker-Fennig, Director for Cancer Imminotherapy Research

at the Dana-Farber Cancer Institute in Boston. Welcome, Kai. Thank you so much for having me. You're welcome. Dr. Lewis Lanier, Professor and Chair of Immunology and Microbiology at UC San Francisco. Welcome, Lewis, to Science Friday. Thanks. Happy to be here.

Nice to have you. Kai, if our immune system is so great, how do the tumors, give us a little primer and how the tumors manage to hide so well from it? So the interaction between tumors and immune cells are extremely complex, and the tumors that actually become clinically apparent, that become the real problem. problems of medicine actually have evolved for a long period of time with the immune system. And you can think of it as a struggle between the tumor cells and the immune system. And some tumors manage to evade. It's essentially an evolutionary war that is going on. And sometimes the tumors win. And so what we're trying to learn is how tumors outsmart the immune system and whether we can turn that against the tumor.

Usually the immune system is able to recognize a foreign cell, right, and go and work toward removing it. But the way I understand it, that cancerous cells are able to get rid or to cover up the flag that tells the cells that we are cancerous? Well, it's actually very interesting. The immune system is incredibly adapt at recognizing foreign invaders, for example, a virus, and that's because all of the proteins in the virus are distinct from human proteins. So it's actually fairly straightforward for the immune system to identify the virus and to kill

the infected cells. Now, tumor cells actually evolve from our normal cells. So in many respects, they're actually similar to our normal cells. And so it becomes a much more complex problem of distinguishing the tumor cells from the healthy cells, and when we do immunotherapy, how we stimulate immunotherapy without damaging healthy cells at the same time. So tell me about your work. Your work does a nifty trick

preventing the cancer cells from hiding? Yes, so our work actually builds on the pioneering work of Dr. Lanier. So Dr. Lanier actually discovered a very important mechanism that allows immune cells to eliminate, stress cells in the body. So stress cells can be infected cells or tumor cells. And so essentially what these cells do is they put up molecular flags and that allows cytotoxic cells in the immune system to kill these stress cells. It's a very powerful immune defense mechanisms. But in many human cancers, tumors evade this process. And so what they do is,

they literally cut these immune recognition molecules off the cell surface, and then the tumor cells become less visible to the immune cells. So what we did was to figure out how we can prevent this cutting of these immune stimulatory molecules on the cell surface, and we found that this elicits a strong anti-tumar immune response. Did you find this working in people? We found this working with human cells. This was actually inspired by a clinical trial performed by my colleague Landrenov at the Dana-Farber. And then we developed antibodies, tested them on human cells and human immune cells. Then we moved it into an animal model to look at it in the context of a fully functioned immune system.

And then we actually developed a humanized model to check whether, again, it works with human cells and with, human tumor cells. Dr. Linnea, tell us about these natural killer cells, how they fit into the bigger picture of our immune system. Okay, well, natural killer cells were discovered back in the 1970s, and at that time, it was shown that if you take some of your blood, put it in a plastic dish with cancer cells, they can kill them. So we've been trying to understand how that happens and how that operates. About 20% of your white blood cells, in fact, are these natural killers. They have an intrinsic ability to destroy cells that are either infected by viruses. I think that's why they were really evolved, or the tumor cells also become stressed like a virally

infected cells and can put up some proteins or flags on the surface to allow them to see the cancer and kill it. And they work really quickly because you already have about 20% of these cells in your bloodstream. So I call them the Marines. They're the first ones on the beach to take out these cells which look abnormal. So the system that Kai has really made a great new discovery about is a way to keep the cancer cell from getting rid of those stress proteins, keep them on the surface so these killer cells can go in and attack and get rid of the cancer cells. Before, it's a game of hide-and-seek.

A lot of tumors do display these stress proteins, but then say, aha, I can evade these killer cells if I cut them off and make them soluble and make them not be on my surface, so I'm invisible. I think the first time we all in the public heard about immunotherapy was when President Carter talked about it and his run in with cancer, and we heard the word immunotherapy helping remove the cancer from his body, you know, when people, I think, erroneously said he was cured. But now it seems to be progressing and we hear news about it more often.

How fast has the field of immunotherapy grown in recent years? As I say, I still remember when it was a novel idea, Kai. So this is one of the most dynamic areas of cancer research and actually all biomedical research. The speed of discovery and clinical translation is extremely rapid. there are more than a thousand immunotherapy trials, clinical trials ongoing right now. And there are a lot of interesting ideas. The most advanced approach are these checkpoint blockers.

So these target breaks in the immune system. And these antibodies now are proved for a number of different cancers, ranging from melanoma to lung cancer, renal cancer, bladder cancer, lymphomas, and many other cancers. But how successful? How successful? What is the cure rate on these? So I would measure the success rate in the durability of the therapy. And this is why this is such a game changer.

So with conventional cancer therapies, be it radiation or chemotherapy, you induce a transatlantic. response, the cancer comes back, it becomes even harder to treat. And so the reason immunotherapy is a game changer is because a substantial number of patients have durable responses that last for many years. And so what it teaches us is that when we elicit the right type of immune response, it can actually keep a cancer in check for a long period of time. Now, the problem, so that's the upside. The problem is that it is still not effective in the majority of patients, and there are a lot of good reasons for this, and a lot of these relate to these evasion strategies that Lewis just mentioned, that cancers have ways of evading an immune response, for example, by cutting immunostimulatory proteins from the cell.

surface. And so what many labs, including mine, are doing, is to figure out what these evasion mechanisms are and to develop clever molecular tricks of how to deal with them. And so I think what many of us are seeing is that this is a very rapidly evolving field. There are a lot of fantastic ideas. And they get translated much more quickly than in the past. into novel clinical trials. So when will we see a higher, I know what you talked about, what you mean by success rate in that, in the people it works and it works for years,

but if we're talking about a 25% rate in melanoma patients, how do we get that number up in all the cancers? So to put the melanoma data into perspective, so this is in patients with advanced metastatic melanoma, In the past, almost all of these patients would die. And now in this disease that used to be very deadly, a substantial number of the patients actually become long-term responders or, you know, in essence, cured.

So the way we get the response rate up is by improving the immune response that exists, but also bringing new players of the immune system. system into the game. And this is why bringing in K cells into the attack is actually very important. The killer cells. Yeah. So the killer cells, the natural killer cells. So the current immunotherapies work by targeting a certain type of immune cell called a T-cell.

And T-cells are very powerful, but many advanced cancers find ways to evade an attack by a T-cell, but they may still be sensitive to an attack by a killer cell. So the way I think about it is that the immune system is like a Swiss Army knife. It has many different tools. And when you have a complex problem, like an advanced cancer, you want to use multiple tools at your disposal

and figure out what is the most sophisticated way of them working together the way they should be. I get it. Dr. Lanier, I'm sorry. I just wanted to get to the another problem with ramping up the immune system is the side effects. I mentioned before type 1 diabetes, gut problems, the immune system even attacks the heart. Are we learning how to prevent these side effects? Well, there's a lot of studies going on right now to be able to predict which people are going to get the side effects,

because the majority don't get the side effects. The majority, you know, have an anti-cancer effect without causing that. but since people are very genetically heterogeneous, we're going to be able to look in the future, I think, and say, well, if we use this therapy, you're at higher risk of getting diabetes or thyroiditis or other side effects. The other thing that I think will happen is we start to be more precise. Right now, we're using a blunt tool of taking the brakes off of all of the immune system checkpoints so that if you have T cells that see the cancer and allow them to go loose, That's good. If you are predisposed genetically by having predispositions in your family for autoimmune disease, and you let those cells go, it's bad.

However, if we can now only engage the cells that can see the cancer but not see you, that will then make a huge leap forward. And I see that happening. We're getting smarter about this as many studies going on right now about how to make those predictions and also how to manipulate the killer cells, both with drugs, but also genetically, to make them more specific for the cancer. Amira Flater, this is Science Friday from WNYC Studios, talking about cancer immunotherapy. Do you get discouraged when you do your research about how slow it's going, or do you feel optimistic about how fast it's going?

I think scientists have to be optimistic. I mean by nature. So my answer to this is that, I mean, so I've done this for more than 25 years. And so the science moves so much faster. The progress is so much faster than it was even five to ten years ago because our tools have gotten so much better. We have the whole genome sequence at our disposal. We have advanced techniques. for interrogating immune cells, both in humans and in animal models.

And we also have new types of therapeutics. And so in my lab, you know, things are literally exploding right now. I mean, we have a number of approaches that are, you know, advancing towards clinical trials. And I see this across the field that there is a remarkable acceleration of progress. That said, cancer is a very difficult problem, and it's important to remember that there are cancers for which there has been no significant therapeutic advance for 20 or 30 years. So, for example, glioblastoma or pancreatic cancer. So what I'm trying to say is that when you get immunologists on the air, they always say how a great immunotherapy is.

but, you know, and I'm certainly one of them, but I also want to say that cancer is a very challenging problem. We're not going to fix it in the next, you know, two to five years, but we are definitely making a lot of progress. Would you agree? Yeah, I certainly agree. This is the most exciting time in my life. I've been working on cancer immunology since I was a PhD student in the 1970s,

and curing mice back than of cancer, it's remarkable that it's now working in people. People, as you mentioned, one in four who were going to die of melanoma, are now living 10 years or more. So we've seen such great progress, and I see no reason we're even getting smarter now and having better tools, as Kai said, to be able to make this work much better, so I'm optimistic. So part of the treatment is just to keep people alive long enough to be around for the new tools. that can be used.

Yeah. That's definitely part of the game, yes. And I'm glad to see that you're both optimistic, and we will follow this because I read about this. You know, we read the journals every week and see new studies coming out, and that's why I wanted to have you gentlemen come on and talk about it. Thank you both for taking time to be with us today. Thank you so much. Thank you. You all.

Dr. Kaewuk-Feraneg, Director for Cancer Humanotherapy Research at Dana-Farber Cancer Institute in Boston, Dr. Louis-Lenian. here, Professor and Chair of Immunology and Microbiology, University of California in San Francisco. My cold is getting the better of me. We're going to take a break when we come back. Spring is finally here, so after the break we'll celebrate by talking about bird calls. And not just the typical songs you're used to hearing, so stay with us. We'll be right back after this break. You're listening to Science Friday.

I'm Ira Flato. You know, spring has officially sprung, and one of the first signs of this season, Those early morning birds, oh, I love them. They start chirping outside your window. You know, every bird species has its own song, but sometimes the call can come from an unexpected place. For example, can you guess what bird makes this sound? Did you hear that?

Maybe we'll play it again. It's hard to listen again. Wow, sounded like a little toy helicopter or something. But that sound is made by the tail feathers of a hummingbird, zooming by. Researchers published a study this week in the journal Current Biology looking at this type of tail feather call. Christopher Clark is an author on that study. He's also an assistant professor of biology at UC Riverside. Welcome to Science Friday.

Thank you. Good to be here. What kind of hummingbird was that? Yeah, that's a Costas hummingbird, a species that we have living in my backyard and on campus in Riverside in Southern California. And this bird does a sort of dive-bombie. Is that where the sound comes from? Yeah, exactly. So the males have these courtship territories that they set up at the beginning of the breeding season. And they have a couple displays that they do for the females,

but the one that you just played, the male ascends about 30 or so meters or 100 feet up in the air, and then dives at high speed past the female and has his tail spread for a good part of that dive, making that pitch or that high-pitched sound. So what is the bird doing with the feathers to create this sound? So they've evolved. So the tail is basically a musical. instrument and they've evolved really narrow outer tail feathers. And so when the male spreads his tail, the inside edge of that outer tail feather is fluttering up and down at that pitch that you heard.

And then the sound is being amplified by the neighboring tail feather in order to generate the sound that they can carry for quite some distance. And this is done for what reason? It's a mating display. It's a courtship display. Why did I not know that, of course? Yeah. And so we actually have a clip of this dive. Let's hear that now. Those are four different, four different hummingbirds, correct? Yes. Yeah, that's right. So I've spent the last 10 years or more studying this whole group of hummingbirds and the sounds that they make with their tail feathers and also with

their wings. So the tail is basically a musical instrument and it's evolved to have a different shape in each species. So that's kind of like one species having a guitar, another species having a ukulele and so on. And then the other thing that you heard going on in that clip in all of those species they were making sounds multiple ways. So in some of those, they were making tail sounds as well as wing sounds. And in one of the examples in there, they were making a vocalization, a mouth sound as well as a tail sound. All right, let's listen to them again. There are four different sounds here.

So perk your ears up on this one. Wow. Do they keep going on and on repeating, or is it just one quick sound like that? Most of the time, when a male is displaying to a female, he'll perform over and over and over again. And the different species are different. So some species do just do one dive, but Black Chain Hummingbird, the first sound that you played, they'll make that z-dood-dood-do-do-to-to-to-to-to-t and repeat that 10 or 15 or 20 times in a row. Wow.

And do we know if the females are actually responding? We don't have any direct data on female preferences or, in fact, we also don't know who the females are mating with. So those are areas that we hope to study in the future. but if you sit and watch a female as the male is performing the display, there's a number of times, and the female very carefully tracks the male with her head as he flies by. I've also seen females even have their eyes closed, almost like a person listening to a symphony or an orchestra with their eyes closed to better appreciate just the acoustic component of the display.

So certainly from observation of birds on their territories, the females are into this. They are most certainly evaluating males on their displays, and we just don't know exactly what part of the display they're evaluating or who they're deciding to mate with exactly when one female goes. Basically, what they'll do is a female will visit one male and then presumably she visits another male and visit several males and then decide which male she wants to mate with.

Wow, wow, that's quite interesting. Let me bring on another guest. When you hear a bird song, you probably think it's a male trying to woo a mate, just like that. But certain female birds are also singing and making calls, and my next guest is here to tell us what they're saying, and she's collecting their call through a project called female birdsong.org. Lauren Benedict, Associate Professor of Biology at the University of Northern Colorado in Greeley.

Welcome to Science Friday. Hi, thanks for having me. How did you get interested in all these bird call? Well, I've been interested in birds and bird songs for a long time, and I really started looking closely at California toways, which are these little drab-brown birds that everyone said were uninteresting. And when you look closely, you find that the males and the females are actually really communicating with each other with this individual duet vocalization. And I thought that duet was so fascinating.

It wasn't just the male song that was really influencing behavior. It was the female responding, too. Yeah, and that's interesting because, you know, we usually don't think of the female birds making the calls. Yeah, I think there's a definite bias to assume that pretty much any bird song that you hear out there is a male. and it's true that in North America, so in the U.S., most of the songs that you hear are given by males, but certainly not all of them. And we really want to draw awareness to that, and we want to ask everybody, if you hear a singing bird, look closely. Make sure you know if it's a male or female, because it could be a female. And you collect these female birdsongs through your website.

Have you seen any patterns so far? What type of female birds make bird songs? Yeah, we're just getting going with this project, and we love having more people upload songs so that we can start to find bigger patterns. So far, generally, it seems as though females do sing an awful lot more in tropical locations. We know that a lot of tropical species have female songs, and in some tropical species, females actually sing more than males do, which we're not used to if you live in the United States, maybe. but it also seems that the species with female song are often ones where the partners will mate for life and they're non-migratory. So that male and female are doing similar things day to day. They're defending a territory.

They're doing similar behaviors to raise young and take care of the nest and all of those things. So whenever we have males and females that both live on the same territory year round, that really seems to be where females sing just as much as male students. Now, let's get to some of the calls that you have given us. You study the Canyon Wren. Let's hear the difference between the male and the female calls in that species. So first, let's hear the male call. Okay. Now, let's hear the female call.

Wow, they're different, Lauren. Yeah, aren't they strikingly different? Yeah. Why is that? Is that so they can distinguish between one and the other? I think that's a pretty good guess at it, and we're actually working to figure that out. And the male song is sort of the iconic. sound of Western canyons. People know this song and love this song. It's such a beautiful

song. And I've had so many people say to me, oh, I've heard that other sound, the female song sound. I didn't know what it was. But once you really start looking at the birds, you recognize that females sound totally different from males when they do that song. And maybe it is because they need to signal something that includes that they are a female. Are they responding to a male call or do they initiate that on their own? They sing it on their own, and they actually do sing less often than males. Males, if you go out into a canyon, you'll hear the male song all the time, and you'll hear the female song only occasionally. But they definitely sing when they have another female nearby.

And so it's probably a signal to those other females, and the fact that it sounds different from the male song allows them to have their own kind of private communication channel among the females. That's interesting. Christopher Clark, as someone who studies the hummingbirds, do you know a female? hummingbirds create songs or calls? Oh, that is an excellent question. In fact, I have a paper submitted to an ornithology journal that, for all I know, Lord, might have been a peer reviewer on describing female song in Costa's hummingbird. So it's not published yet, but yes, there are examples of hummingbirds that do that too.

What do they sound like? What does a female, give me a little limitation? So, okay, so the Costas hummingbird, the sound you played a bit ago was made with the tail feathers, and it was a... One of the really funny things about Costas hummingbird is their vocal song. sounds very similar to that. It's kind of this with just this little break in the middle and the female costas that we found

were singing more or less exactly that same song. So they also sounded just like the males. There are some species of birds, Lauren, where the male and a female duet with each other. And I know you have a clip, and we're going to play that clip for us right now. It's quite fascinating. So which bird Lauren started it first? The male? Yeah, isn't that a beautiful song?

It is. That's a Venezuelan, Venezuel and the male begins and the female is then joining in. And you can sort of hear that if you listen for it. And in that species, actually, sometimes females will begin and males will join in or it can go the either way. They generally sometimes sing alone, but then either sex can join its partner and sing these beautiful duets. And Christopher, when does a hummingbird decide it's going to vocalize versus using its tail feathers to create a sound? A lot of the species that, a lot of species do both. So a pattern that seems to hold is that in the group of hummingrids that I study,

the males either make wing sounds or they sing to guard their territory. And then if they sing or if they make wing sounds, they also include those in some of the displays that they do for females. And then in addition to that, they also have a dive that they do. And they have, basically, they have to dive and go fast in order to, get fast enough to make their tail feathers make sound. So it's not an either-or. It's like, you know, just like humans, we both vocalize,

but we also make non-vocal sounds by clapping our hands. A lot of the birds that make non-vocal sounds have a variety of ways that they make sound. So it's not just a one or the other. You know, I try to attract hummingbirds to my feeder in the backyard. I've been, you know, mildly successful. Can I hear these sounds? Can I position myself?

Are they audible to, you know, non-experts, like we lay people? Oh, absolutely. The hearing range of birds is, we don't really know how well they hear high frequency sound, but it's about the same frequency range as humans. And so basically, if a bird can hear it, so can you, and vice versa. And so some of the sounds that the birds make are somewhat quiet, some of the wing or tail sounds are somewhat quiet, and so they might be easy to overlook. Also, cost of something good in particular, the sound is so high-pitched that it's hard to localized. And so when a male is diving, I mean, I've spent years studying them, and I still sometimes have a hard time spotting the male. He's tiny. He's flying at the speed of freeway traffic. And so you can

hear the sound and look around and not see the bird. And so you don't know what it is where the sound is coming from. But in fact, if you know what you're listening to and know what to look for, sure enough, there is a male shooting by at 60 miles an hour as he dives to a female. Wow. Wow. I'm Ira Flato. This is Science Friday from WNYC Studios. 60 miles an hour, did you say? Yeah, 60 miles an hour. The whole point of diving, the bird ascends to a height, and then it uses gravity to speed up and go faster in the dive than they can in level flight. Hummingbirds are really good at flying, and when we measure them in wind tunnels, they can fly 40 miles an hour or so at their top speed.

But, yeah, the maximum speed we've measured in a dive is about 60 miles an hour. Lauren, how much does environment play a role in how these calls? or songs develop. If there's one species, but populations that live in different areas, can they communicate? Do they develop some sort of bird song dialect? There are birdsong dialects, and we don't know how much of that is driven by habitat and the environment or just learning kind of the local language or dialect when you move to a new place.

And in fact, there are species in which males sing dialects. They might only be separated by, say, a few miles from another. dialect, but they sound different, just the same way that we might say that a fizzic carbonated drink is soda, and somebody else might call that pop. Birds do that, too. And females do the same thing. So in, for example, white crown sparrows, they're really well known for males having different song dialects.

If you get females to sing, they will also sing the same dialects that those males do. Does this tell us anything about the evolution of bird calls in birds? Yeah, that's a really fascinating question. And actually, something we know about female song is that the ancestor of songbirds seems to have had song that was given both by males and by females. So in places where females don't sing, it's not because the males suddenly became fancy and left the females behind. It's probably because the females lost that trait for some reason.

So instead of asking, why did males start singing to really understand the evolution of this trait, we need to ask. why is it that some females stop singing? What is it about certain environments or certain places or certain lineages of birds that that female song suddenly became less advantageous? So you think that they both were singing originally and then the females just stopped singing? Yep, that seems to be the case. Yeah, or that the females reduced singing and just don't sing as much as their deep ancestors might have sung.

Christopher, is that the same with hummingbirds? Well, we know much less about song in general in hummingbirds than we do in past. Sassarines or some other groups. So as I mentioned, we do have an unpublished case of female song in one species. A lot of hummingbirds sing. There are some species that have evolved to, for the males don't even sing. So neither males nor females sing. Those are the ones that produce sounds with their wings when they fly around. And when they do, it's the males that produce the sound primarily. The females sometimes have a really slight version of it, but it's not clear if it has separate function in females. It might just be a male thing. So in hummingbirds, which are

distantly related from the songbirds. As far as I know, my guess is that song is primarily a male thing, but I could be wrong. I mean, one of the fascinating things about Lauren's work and the attention to female song is that it's been incredibly overlooked in passerines, and maybe it's also been incredibly overlooked in hummingbirds. It might be that if we actually go out and look, we'll find female song in many more species of hummingbird. Lauren, are you looking for people to send you recordings of birds?

Always. Tell us how to do that. So on the website, femalebirdsong.org, it gives lots of tips and suggestions. And for all of you out there who are listening to and recording birds, if you use eBird, you can upload sound files through EBird that go directly to the Macaulay Library of Natural Sounds, and you can tag those and indicate on the meta-information that it's female song, and that then makes it available for anybody who wants to look in the library. They're also great libraries through the xenocanto.org has a library,

and then other data, just observational data, you can always put into something like Ebert or I Naturalist or other public databases noting your observations of female song. And there's some great stuff we can do this weekend. Laura Bennett, Lauren Benedict, Associate Professor of Biology at the University of Northern Colorado in Greeley, Christopher Clark, Assistant Professor of Biology at the UC Riverside, and you can listen to all of those bird calls up on our website

at ScienceFriday.com slash bird calls. Thank you both for taking time to be with us today. One last thing before we go. Science Friday's hitting the road from Pennsylvania next month, taking the stage at Pittsburgh's Carnegie Library Music Hall. Saturday, May 19th. We have roboticists and artificial intelligence designers, musical robots, musical humans, too,

Pittsburgh's own townspeople. You get more info and tickets at ScienceFriiday.com slash Pittsburgh. ScienceFriety.com slash Pittsburgh. That's going to be Saturday, May 19th. BJ Leiderman composed our theme music, and we'll just say, have a great weekend. I'm Ira Flato in New York.