Instant Genius - Sound in the animal kingdom, with David George Haskell

Episode Date: April 17, 2022

Biologist David George Haskell, author of Sounds Wild and Broken, explains how and why the animal kingdom evolved to communicate by sound. Once you’ve mastered the basics with Instant Genius, dive deeper with Instant Genius Extra, where you’ll find longer, richer discussions about the most exciting ideas in the world of science and technology. Only available on Apple Podcasts. Produced by the team behind BBC Science Focus Magazine. Visit our website: sciencefocus.com Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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In this episode, I talked to biologist David George Haskell, author of Sounds Wild and Broken, about the evolution of sound in the animal kingdom. So in your book, you say that life on earth was silent for the first three billion years after it formed. So what was it that kickstarted the sensing of sounds in animals? Yeah, so the ability to sense sound emerges from tiny little hairs on the surface of cells. And this is one of the remarkable things about hearing, even though that, of course, it takes really different forms in humans and fish and lobsters and other animals that hear today. At root, there's a cellular unity. So these little hairs called cilia pick up motion in the environment around them.

And for aquatic organisms, of course, that's motion in the water. For those on land or on air, the hairs are not quite so sensitive. So you need a thing like an outer, a middle, and an inner ear to convert the little vibrations in air to vibrations in water, which is what happens in our inner ear. So we humans actually listening in an aquatic medium in the deepest part of our ear in the coils of our in the ear. So right from the get go, animal life, and indeed probably the creatures that came before animals, single cell organisms and bacteria were sensitive to vibrations around them. So right from the start, there was a sensitivity to vibratory energies, which makes sense. If you're a cell or a small animal trying to make your way, you need to know what's happening around you.

One of those ways of knowing is through picking up vibrational energy. So from the start, there was a sensitivity, often very crude at first, particularly good for low frequencies, not so great for high frequency sounds, that then took different forms in different creatures. But what's astonishing to me is that even though hearing, and by which I mean sensitivity to vibrations, is very, very ancient, is ancestral to all animals. Communicative sound,

so animals making a sound whose evolutionary intent is to call attention to themselves or to send a warning, that evolved very, very late. In fact, the first physical evidence we have for communicative sound is not until 270 million years ago when we have a fossil insect that has sound-making structures on its wings. Before that, you've got hundreds of millions of years of animal evolution where we don't have any fossil evidence for any sound-making structures.

Now, those animals were making sounds by crunching on food and flipping their flippers around and walking on sandy shores. But those were incidental sounds. They weren't communicative. So it took a long time for communicative sound to evolve probably because it was so dangerous to make a sound. It's no accident that even to this day, it takes a certain measure of fearless verve to be a sound-making creature. Who makes sound birds, flying insects, some mammals.

These are creatures that can get away from predators rather rapidly, or fast or well-defended fish and lobsters. Salamanders and jellyfish and snails are silent because it's too dangerous to make a sound. So you mentioned there the fossil of this, the first, it's a cricket, I believe. Yeah, it's a cricket-like creature. So could you tell me a bit about that? I think that's a really interesting point to follow on from. So this creature is called Permostridgulus.

It's found from Permian Age rocks, so 270 million-year-old rocks, from the Massif Santal in France. So from some rocks in the south of France, discovered in then 1990s, and the fossils that we have are of the wings of this insect that look something like a little cricket. And on those wings, there are some raised ridges, and those ridges have a series of nubs on them that look very similar to the ridges and nubs on modern crickets and bush crickets and Katie did, modern singing insects.

Now, this creature was not a true cricket. The ridge was on a slightly different part of the wing than modern ones, so this isn't a direct ancestor. But it does seem to be the first physical evidence of a sound-making device, because that ridge has no other known function on the wing. And it looks, of course, very similar to the ones in modern creatures. And so you can do a speculative reconstruction of what this sound might have been. It was a ridge about the size of a modern mole cricket, fairly widely and unevenly spaced little nubs on the ridge. So it was probably a fairly coarse rasping sound. it make. So, like, as you say, modern insects also make sounds in a similar method. But how exactly

does that work? How does this ridge allow them to create a sound? So what they do is they rub one wing over the other. And at the base of the wings, they have these ridges. And in modern insects, one, I mean, it depends a little bit on the insect, but one way of doing this is to have one wing that has the ridge with a whole load of tiny little very evenly spaced teeth on it. And the other wing at the other wing is like a little plectrum, a scraper that goes over the top of that other ridge, like running a fingernail over the top of a comb. And this action, which is all just called stridulation, makes a brup, brup, and I'm not very good at doing it, but the insects are amazing.

Some of them can make pure-toned sounds of exactly the same frequency every time they close their wings. Now, 270 million years ago, the ridge was not nearly quite so, so spacing on the teeth wasn't so even. It was a much cruder design. There's been hundreds of millions of years of evolution to finesse things. But I think it's interesting that these soundmaking things are on the wings, because a wing, of course, didn't evolve to make sound.

It evolved to fly. And yet very soon after the evolution of insect wings, which is about 300 million years ago, evolution repurposed the structure to make a sound, and the wing, an insect wing is a little bit like a modern loudspeaker. It's a papery surface attached to pulsating muscles, like the cone in a loudspeaker attached to the coil that makes it pulse and sends sound outward. So insect wings not only allowed insects to get away from predators, which then allowed them reduce the risk of making a sound, in a way wings freed sound. I'm sure we could come up with all sorts of bad analogies and terrible songs

about soaring on the flight of wings allowing a song to soar into the air. But quite literally it's true in terms of insect evolution. So not only did insect wings allow a certain measure of safety, but they also formed the structure that turned out to be pretty good at allowing sound to evolve, sound making, communicative sound making. Yeah, so it's sort of following on from that, there's an interesting section in your book where you mentioned that the evolution of sonic communication

kind of went hand in hand with the evolution of flowers. Yeah, and it seems like an absurd thing to say that somehow flowers are involved with the diversity of sounds in the world, because one of course the striking things about sound and soundscapes is how varied they are. You know, not every frog makes the same chirp, not every bird is making just some grunt that advertises how healthy it is. No, there's an extraordinary amount of diversity. And part of that diversity, I think, and if we look into deep

time, was triggered by the evolution of flowering plants. Why? Well, flaring plants are champions at connecting to other species. Below ground, flaring plants connect with nitrogen-fixing bacteria. At least ten different separate evolutionary events where nitrogen-fixing bacteria glommed on to flaring plants. And so in a way, the flaring plants fertilized the soil, accelerated the productivity of ecosystems, below ground, and then above ground, flaring plants and their fruits co-evolve with insect pollinators and with seed dispersers and with herbivores,

and this back-and-forward evolution between flaring plants and insects, and then indirectly mammals and reptiles and birds, unleashed an enormous explosion in diversity. If you look at the family trees of many insects, right when flowering plants become very abundant and diverse, so too do the family trees of these insects. And any time you have an explosion of speciation of new forms emerging, you provide new raw material for sensory communication, both chemical communication and sonic communication, visual communication, literally a great flourishing or blossoming of communicative modes within the animal kingdom

as a result of the evolution of flowers and flowering plants. So we've talked about insects there. But how about, you know, obviously we're speaking now, you know, mammals are great sonic communicators as well as birds. So where does that sort of fit into the evolutionary picture? When do we start getting birds and mammals communicating sonically? Yeah, well, you know, birds are an interesting case because they evolved, you know, about 155 million years ago. First bird-like creatures, essentially feathered dinosaurs, making, diversifying into all sorts of ecological niches.

There were some of those early birds that looked like sparrows, some more like penguins, some like hawks. in a very, very early flourishing and increase of ecological range of birds. But many of those early birds, it seemed, didn't have the structure in their chests that modern birds have. And that structure is called the syrinx, the confluence of the bronchy going up to the trachea. There's this extraordinary structure that when we hear a blackbird singing or a crow cowing, that's what we're hearing is the sounds produced by the syrinx. the first fossil evidence of the Syrinx is until about 68 million years ago, right before

the mass extinction that wiped out most of the birds. So when the meteorite hit at the end of the Cretaceous period, most of the bird diversity of the world was wiped out because that meteorite was particularly bad for forest-dwelling creatures of which the birds were significant members. And so luckily for our ears, I mean, this is a sort of human-centric evolution doesn't work this way, but we can look back with an aesthetic appreciation to that, you know, that mechus extinction, the few birds that made it through were some of the ones that had the syrinx. And after that, they repopulated the world with this form of bird that can sing with this extraordinary structure. And so we hear the evolutionary legacy of renewal

after a massive loss when we're listening to birdsong. Mammals, on the other hand, are in inherited the reptilian top of the larynx, you know, the windpipe as a way of squeezing the sound and making hisses and grunts and bellows the way reptiles still do to today. But what a really amazing thing that happened in an unexpected thing for sound evolution and evolution of mammals was the evolution of lactation. So our great, great, great, great grandmothers in proto-mammalian evolution started lactating, producing this incredibly nutritive gift from the mothers to their offspring that allowed the offspring to grow really fast, all kinds of ecological, physiological advantages to milk. But in order to receive

that milk, the young needed to suckle. And no reptile mouth can really suckle very well. And so the mouth and the throat and the jaw of early mammals became more sophisticated, more muscular. The bones expanded and became more complex. We can still feel this in our throat, the hyoid bone that sits underneath the jaw is a very sturdy thing. This allowed mammals then to take that suckling apparatus

and put it to all sorts of other uses, including what I'm doing now, which is using my throat and my tongue and my lips and my hyoid bone and the movements of my jaw to sculpt sound in highly sophisticated ways. So mammalian vocal diversity, we owe our vocal diversity to many things, but one of them early on was the gift of milk from these great-grandmothers to their offspring that reworked our jaws. Now, of course, humans have a particularly sophisticated way of speaking, but, you know, when we hear some marine mammals or wolves howling or red deer doing their bellowing, all of them are using this mammalian apparatus to make extraordinary sounds.

I mean, we can't hear it, but mice and rats have a sort of little ultrasonic songs that they sing to one another. And so they've reworked that mammalian gear, that kit, if you like, into a way they're making ultrasonic sounds that only recently have we become aware that they're making these little chirps at one another in songs. So, as you mentioned there, like birds sing, I mean, some of them are incredibly complex songs. Like in the book, you mentioned the lyrebird, which is sort of nature's great. mimic. Yeah, you know, but birds aren't. I mean, the libeard is a champion, and when we're attracted to the liber bird aesthetically because it's such a good mimic, it copies others, including, I mean, there's famous David Attenborough clips from the life of birds, you know, hearing the camera shutter and the chainsaw sounds going from the lyrebird. And interesting, the lyrebird does

not have a particularly complex syrinx, so it shows that even without all the sophisticated muscles that say a sparrow or warbler has in its chest that the liebird can still make that really complex sound. There are other incredible mimics like the mockingbird in North America. Most birds, though, are not doing the DJ's work of sampling their environment and putting it together in cool ways. That's one fairly unusual way of making sound. What they're doing is listening to their own species the way we do. I mean, a human child growing up is listening to all sorts of sounds, but is particularly focused on the sounds that come from its parents and those around it. And the same is true for many songbirds. And so humans and birds in a way are strangely

linked because not only are we sophisticated vocal beings, but many, many birds and all humans are vocal learners. And this is something that actually separates us from many of our close primate cousins, which have sophisticated cultures, chimpanzees and gorillas, There's amazing cultures. It takes years and years for a young chimpanzee to learn all they need to learn to be a successful member of their society. But they learn that mostly through observation and through touch, not so much through vocal communication.

That's part of it, but nothing in the way that humans do. So humans have taken primate great ape culture and merged it with a bird-like way of using sound, and that's where we get human language. So our language in a way is almost chimeric, is that we've taken things that other species do and combined them in one magnificent thing, which is spoken human language, that then in the last few thousand years, we've written down. And so what was always ephemeral is now found, can be fossilized, if you like, onto a page or onto a computer screen and stored. and so sound can transcend the singer or the speaker and reach across the centuries or reach now with the digital world instantaneously around the world. So we have an extraordinary way of putting together pre-existing talents of other species.

Our vocal apparatus is not particularly complicated compared to, say, birds, but boy, the way we put together things in our brains to combine vocal learning with culture gives us a lot of power. So when we're talking about studying evolution, it's always quite a lot of detective work. So I think a lot of people listening will be thinking, well, you know, how do we know all of this? How do we know how this came to be? Yeah, well, partly some bit we don't know. And that's, you know, there's been so little attention to the deep evolution of sound. You know, in writing this book, it took me months to sift through the legislature.

And there are a few people who've looked at this before and tried to synthesize things. But compared to the evolution of other things like legs and eyes and mating appendages and body armor, which have been really well studied, thousands of papers, the study of the deep history of sound and sonic communication is very much underappreciated. Pomoestrigilus, the fossil that we discussed before, there was no media attention whatsoever to the publication of that paper. It's still a relatively obscure paper. And this is the first communicative. singer in the whole known universe? Surely we should, you know, have some attention to this. And so I hope one thing I can do with a book is stimulate interest in this. And I'm sure within a few years, new fossils, new insights will come. And, you know, what I've written will be entirely superseded and falsified and progress will be made. But piecing together this in the past is very

difficult. So how do we do that? One, by looking for direct evidence in the fossil record of sound making structures. For example, stridulating structures on an insect's wing. There's an example from the Permian, but there are more sophisticated examples from the Triassic and the Jurassic, and so we can know that those animals were making sounds because the structures look just the same as the ones in modern animals. Same with the avian syrinx or stridulating structures on crabs and lobsters. The other way is indirectly through genealogical trees. So within the frogs, for example, there are some frogs in New Zealand that branched off from the rest of the frog family tree very, very early before 200 million years ago. And we know that from a combination of fossil evidence and from the genetic clock that we use to piece together the timing of the pedigree of animal lineages.

So we can say, and those creatures in those little frogs in New Zealand are silent. And so it was after that, after they branched off, that the singing, the ability to sing evolve within the frog lineage. And we can estimate that singing frogs probably arose around 200 million years ago based on that family pedigree. Now, that estimate is contingent on and dependent on the quality of the evolutionary tree. And it can always be revised when somebody draws a more accurate tree or finds another fossil that sheds light onto it. The same with humans, and we can say that our hyoid bone and the genes that are involved in making sound and vocal culture and language were present probably about 500,000 years ago, so half a million years ago. We know that both from physical evidence of the hyoid bone in fossils and archaeological evidence, and then also from the genes that we find in Neanderthals and Denisovans, who seem to have. have some of the same genetic gear, if you like, the same gene sequences that are required

in modern humans to make sound. So we can piece together our own evolutionary past in a hazy way. You know, it's not particularly accurate in the way that later on, say, with the evolution of musical instruments, we can get a lot more precise. Forty thousand years ago, we found the first evidence of musical instrument making in caves in what is now southern Germany, and those can be dated with great precision because here's a flute buried in the cave sediment. With the evolution of something as ephemeral as language, it's a little harder to pin it quite so accurately with the date. So up until now, we've spoken mostly about land animals, but obviously there's a lot of communication going on in the water, in the oceans. So how do they, how do they different types

of communication differ? Yes, and this is one of the revolutions that we, I mean, in the last few decades, we've learned that how much communicative sound is important within the oceans and the extent to which it's being degraded now by sound pollution. In deep time, it seems that the spiny lobsters, which you can still find in some, you know, supermarkets, they're the big lobsters with a great big antennae and spines all over them. And at the base of the antennae, there's a little track. And when they rub the antennal base over that track, it makes a squeaking sound that can be heard over a kilometer away, and it seems that they may have been some of the earliest communicators in the oceans. With fish, who are many fish now, thousands of them, make all sorts of songs

during the breeding season and warning cries and other sorts of sound in the ocean. They make those sounds often by rubbing muscles on their swim bladders, and that is something that doesn't fossilize so well. And so the early evolution of fish sound making is harder to discern, but we do know that the most vocal, sort of noisy fish species now, mostly evolved, their families mostly evolved about 100 million years ago. So early oceans were probably not nearly as diverse as sonically diverse as they are now. I mean, now if you dip a hydrophone, particularly into some of the warmer oceans around the world, you'll catch dolphins and whales, you know, the famous sort of marine mammals who have their songs and echolocating and sophisticated vocal cultures,

but also snapping shrimp, tiny little shrimp that snap their claws together when they're hunting and when they're communicating to one another, that make these snapping, clicking sounds that raise a silvery cloud of noise in the ocean that is sometimes so loud that submarines during war hide within it. So they get close to the snapping shrimp beds. and the snapping shrimp smother the sound of the submarine so they can hide from their enemies. Off the coast of many productive shores, until we overfished them, there were billions of fish making sounds.

For example, the cod off the northeast coast of North America were there by the hundreds of millions making sounds, grunting, clicking, groaning sounds during the breeding season. And now they're down to just a fraction of their, you know, maybe just 1% of what they were, that those sounds were extraordinary. Millions upon millions of whales in the oceans making sounds. So the oceans, unlike what Jacques Cousteau first told us, you know, his film from the 1950s was called the Silent Ocean, Le Mont du Silas. And, you know, he was reflecting the level of mystery that we had about ocean sounds.

people just didn't know that the ocean was a sonically rich place. Sounds travel very far and fast in the ocean, so it's a different kind of vibe. When a whale, particularly a whale, gets down into the deep ocean, there's a thing called a deep sound channel there that acts as a lens that can carry some of these low-frequency sounds across hundreds of miles across ocean basins. And that lens forms because of gradients in salinity and temperature and so forthers of sound waves get focused into a channel deep down in the ocean. So some very long distance communication,

as well as a lot of things like most fish, like a toad fish that lives in its lair. The male is sitting under a broken old flower pot or under a piece of rock, defending a little nesting hole, and the females come and mate with him and lay the eggs in the male, stays there and defends the eggs and the babies.

He's making all sorts of bleating sounds that carry just a few meters as a territorial signal and as a mating signal in the same way that a common blackbird would be doing in someone's back garden, the same is happening under the water. We just need to have the right technologies to be able to listen into that. In the book, you mentioned that when you're out in the field recording,

you can actually detect many more animals using audio methods than you can see visually. Yeah, so it's true for sound recording now for humans, but this is one of the great advantages of sound, of course, because the whales that are communicating in the ocean, they can't see more than one body length ahead of them when they're down in the deep or in murky, near-shore things. So sound is a great way of being detected across distances

in very turbid habitats. The same in the rainforest. The vegetation is so dense. No one can see anything. And so how do birds and frogs and insects find one another? They use sound because sound passes through and around obstacles. So the same thing with putting on. on headphones and using a microphone dropping a hydrophone, say, into a salt marsh in the United States

or a seagrass meadow in the UK or down in the Mediterranean, you realize that although the surface of the water seems uniform, and honestly quite boring, there's nothing going on, maybe a few birds flying around, but it's like this is very pretty, but there's not much action. the hydrophone reveals this great hidden world that is as diverse as many tropical forests of shrimp and fish and dolphins, all these underwater species communicating to one another in a way that human eyes absolutely cannot detect. And that great diversity also tells us something about the productivity of those ecosystems. These salt marshes or seagrass meadows are some of the most productive

ecosystems in the world and store a lot of carbon and so they're important for our responses to climate change so sound leads sort of it blew me away at just an aesthetic level to be in a in a habitat that looks so uniform but have your ears teach you wow there's a lot of action going on here it was just a very beautiful experience but beyond that it helped me understand the ecological complexities of these ecosystems in a way that directly connected to my senses and wasn't just an abstraction, like a diagram in a textbook or someone just telling me through a graph, you know, look at how productive this ecosystem is. I actually got to hear that and thus to feel it in my bones and understand it at a deep level. And I think that's one of the amazing things of turning on one's ears

and paying attention to the world is we come to understand things that were just as an abstractions more deeply within us. And I think that, I mean, it's a source of joy. It's also heartbreak when we hear things that are broken. But it seems to me more and more like necessary that we do that as a foundation for ethics. If we're not listening to the world, how can we figure out how to be good neighbors and good kin to other species, if we're not actually really listening to them, if it's all just in our heads, a bunch of ideas.

Ideas are important. But ideas dissociated from lived experience, I think, can be dangerous and misleading. Thank you for listening to this episode of Instant Genius. That was biologist David George Haskell. If you want to know more about the science of sound and sonic communication in the animal kingdom, check out his book, Sounds Wild and Broken. Or, to hear him tell me more about the science of sound, head over to the Instant Genius Extra podcast. Thanks for listening.

The Instant Genius podcast is brought to you by the team behind BBC. Science Focus magazine. Finders on sale in supermarkets and news agents or in your preferred app store. Alternatively, do come find us online at ScienceFocus.com. See you next time. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist focal, Name creates high-end audio systems combining innovation with craftsmanship so you can listen to music, just as the artist intended. Discover more at name audio.com.

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