Sunday, May 22, 2022

Animal sounds are a marvel of evolution. We can’t afford to drown them out.

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Earth can be a noisy place. Humans are especially efficient at filling the environment with sounds, from speech to music to heavy machinery. Plenty of other creatures contribute to the global soundscape as well: crickets trill, birds chirp, wolves howl, and whales sing their low, mournful-sounding songs. It’s easy to take these sounds for granted nowadays. But for most of our planet’s history, they didn’t exist.

“For 3 billion years, life was nearly silent, its sounds confined to the tremors of cell walls and the eddies around simple animals,” David George Haskell, a writer and professor of biology at the University of the South, writes in his latest book, Sounds Wild and Broken: Sonic Marvels, Evolution’s Creativity, and the Crisis of Sensory Extinction. “At first, sound on Earth was only of stone, water, lightning, and wind.”

Haskell is no stranger to writing about the natural world. His first book, The Forest Unseen, is a record of the goings-on in a single square meter of old-growth forest in Tennessee, and was a finalist for the 2013 Pulitzer Prize in Nonfiction. He followed that with The Songs of Trees, which explores the webs of interconnections that shape the lives of 12 trees around the world. In Sounds Wild and Broken, Haskell turns his ear to the vibrating air around us to write a book that is equal parts meditative observation of nature and treatise on our responsibility to the planet.

I spoke with Haskell about the first animal sounds, humans’ impact on the world’s soundscape, and the looming crisis of what he calls a “sensory extinction.” Our conversation has been edited for length and clarity.

In the beginning, there were “hums and fizzes”

Neel Dhanesha

What did the ancient world sound like?

David George Haskell

Earth was not silent. There were waves crashing on shores, geologic rumbles and bellows coming from deep down in the Earth’s belly, the sound of thunderstorms rolling in over the horizon, and softer sounds, like the sounds of rain and wind going through the leaves.

But if we could teleport back, there would be no singing insects, no birds, no frogs. It was a strange world — familiar in some ways, but also deeply, deeply alien because this was a different planet than the one we live on now in terms of acoustics.

It was shocking to me, in researching this book, how long the time period was that Earth lacked any communicative sound — the sound that evolved for the purpose of carrying a signal from one creature to another, usually one animal to another. It took hundreds of millions of years after even complex animals evolved for those first communicative sounds to evolve, as far as we know.

Neel Dhanesha

What were the first sounds made by organic life? And were they heard?

David George Haskell

The very first sounds made by organic life were the hums and fizzes of bacteria and single-celled creatures. They’re busy little creatures, chemically. All those reactions and shifts in the cell surface shape cause vibrations in the surroundings, and those vibrations actually stimulate the growth of other bacteria.

So they are sensitive to one another, but as far as anyone knows, they’re not communicating. No bacterium is singing to find a mate or to shout out warning signals.

From the start, life was making some sound. But the question of communicative sound is a different one. The first physical evidence dates to about 270 million years ago, to an insect that looks like a cricket. [The fossil was found in southern France.] The wing of this insect has a little ridge with a row of knobs on it. And there is no function for that ridge that we know of, other than making a sound. When the wings rub together, they make a little raspy sound in a way that’s analogous to how modern crickets and katydids sing. This early fossil, named Permostridulus, has a much cruder device [than modern crickets]. But it’s recognizable as a singing device.

LISTEN: What a Permostridulus chorus might have sounded like

Neel Dhanesha

Why did this cricket-like creature decide to sing?

David George Haskell

Intention is really hard to fossilize. What we can say is that modern insects make sounds partly to attract mates. Perhaps Permostridulus was doing the same — and think of the advantage in doing that, because Permostridulus itself was just a few centimeters long. But if its sound is audible over, say, 10 to 20 meters, it has increased the presence of its body by about 10 or 20 million times in terms of area. It can be found by potential mates with much more accuracy and speed.

So a mating display is one possibility. The other is a defensive signal: If you pick up a lot of insects now, they’ll give a little buzz or chirp that sounds weird and alarming and makes you want to drop it. Lab experiments have shown that mice and spiders and other creatures, when confronted with these alarm chirps, do indeed let go of the prey. Permostridulus may have made a sound to surprise predators and gain itself a means of escape.

Neel Dhanesha

That sort of implies that the animals around this creature could hear it.

David George Haskell

I think one of the reasons that communicative sound took so long to evolve was that right from the get-go animals were sensitive to vibrations in the water or in the air. If you made a sound, you were at risk of becoming someone else’s lunch, so the first singers had to be creatures that could get away quickly. Permostridulus probably had pretty good jumping legs; it certainly had wings that it could use to fly away.

On the vertebrate side, frogs were among the first creatures that made sounds, and they have powerful jumping legs. To this day, frogs are very vocal, but salamanders make almost no sound whatsoever even though they’re just as legit an amphibian as the frogs. Making a sound would be far, far more costly for them [because they can’t jump away].

How animal sounds bloomed

Neel Dhanesha

Your book draws a connection between flowers and sounds, which came as a surprise. How are the sonic world and the world of flowers linked?

David George Haskell

The fossil and ecological evidence is pretty clear that the evolution of flowers, by about 100 million years ago, helped boost the diversity of sound. They did this in a few ways: first, they formed partnerships below-ground with bacteria that turned nitrogen into nutrients. That increased productivity, which then increased the amount of food and energy available up the food chain into the insects.

Even more important, though, is that flowers, by producing nectar and pollen, fruit, and lush foliage, provided habitat for bees, ants, butterflies, moths — you name it. All the terrestrial insects were connecting to flowering plants, where pollinators and herbivores specialized on particular plant families and co-evolved with them.

Every time a new species evolves, there’s a potential for innovation, and so as species split into two and four and eight, the potential for new sounds [and] ways of communication really took off. Flowering plants became a trigger for animal diversification in evolution that then led to more diverse sounds in the world.

Neel Dhanesha

As you write, though, there are two big exceptions to this relationship between flower and sound diversity.

David George Haskell

One is that flowering plants are really not a thing in the oceans. As the continents fragmented and created inland seas and new seashores, and the oceans separated somewhat from one another, that created an awful lot of ecological diversity, which created new possibilities for flourishing and expanded biodiversity. When we drop a hydrophone [an underwater microphone] or a fishing net into the oceans, what comes up through sound or as dinner are the descendants of those creatures that really diversified 100 to 150 million years ago.

Another big exception is mammals. This is our own story — the evolution of lactation and its effect on the human voice. Young animals had to suckle on this incredibly nutritious milk, which is an amazing way for mothers to pass on energy and nutrients instead of just giving them regurgitated food or letting [them] find their own food.

Suckling involves using jaw and throat muscles in new ways. The mammalian jaw and throat was transformed by the gift of milk. Evolution then got to work putting that to use to modify sound. When I’m speaking, I’m using muscles down in my throat and my tongue in the back of my mouth and my lips and my jaw and my hyoid [neck] bone. No reptile can do this because they’ve got very slack, unsophisticated jaws compared to us. They do other things marvelously well, but speaking is not one of them.

Sounds Wild and Broken: Sonic Marvels, Evolution’s Creativity, and the Crisis of Sensory Extinction was published in the US on March 1, 2022, by Viking.
Cover design by Nayon Cho for Viking

A “sensory extinction” is threatening the world as we know it

Neel Dhanesha

You spend a significant portion of your book examining other ways we impact the soundscape, and you write about what you call a sensory extinction. What do you mean by that?

David George Haskell

What makes life work is connections between species and individuals within them. We connect through the senses. And we’re pumping massive amounts of sound into some ecosystems that block the capability of animals to live. There’s a sensory crisis of just total overload.

We’re setting off explosions in the oceans, through seismic exploration for oil, that are audible over hundreds of miles — loud enough to kill things that are unlucky enough to be nearby, and drive away others. Around interstates or heavy industry in some cities, there’s so much sound that insects and birds and frogs can’t hear one another.

Human life also is extremely negatively affected. Noise isn’t just an annoyance; it causes cardiovascular disease, prevents children from learning, and fragments neighborhoods. A sensory crisis is a real crisis causing measurable harm, and also intersects with some of these other problems.

Neel Dhanesha

You write that if there’s a sonic hell, it’s in the ocean. Why not cities?

David George Haskell

For some people in cities, there is a sonic hell. But the city is a paradoxical thing in that — for humans, at least — its sounds can also be a source of energy and vitality.

In the oceans, though, we are pumping the sound in through drilling and shipping and exploring with seismic guns, but we’re not suffering. We are the creatures creating the hellscape for others.

Ocean species are fully immersed in sound. Sound penetrates all of their tissues. They hear it all throughout themselves. We’re immersing these beings who have no agency and no choice in the matter in an experience that is devastating to them.

Neel Dhanesha

In other words, sound can be both an indicator of a problem and also an issue in itself, especially for beings that are particularly sensitive to it.

David George Haskell

It is a problem in itself, and the fact that it is an indicator is scientifically useful because you can then go measure sound.

One thing we’re learning is that alongside the crisis of too much noise is a crisis of silencing. In tropical forests, for example — and we know this from the testimony of Indigenous peoples as well as through digital recording devices in the rainforest — we’re losing the diversity of sounds of living beings from many of those ecosystems, partly through processes that are pretty obvious. When you cut down a rainforest and put a palm oil plantation in, or you turn a prairie in the Midwestern US into corn or wheat fields, you lose almost all species that were there before. When ecosystems change their acoustic signature over time, it’s probably because they’re losing some species.

Neel Dhanesha

Why should people be worried about that?

David George Haskell

I think there are multiple levels for why we should care about the diversity of sound. To have a vital and just future on this planet, we need fully functioning forests, because forests are where medicine and food and fuel and soil and clean air and clean water come from. The same is true for prairies and healthy oceans. By listening to these habitats, we can ensure a better future for ourselves and for those who come after us.

Think of a piece of music. Out of silence comes a brief experience of narrative and form, beauty and connection. That’s what the narrative arc of the planet is doing: coming out of and going into silence, with a brief expression of beauty and form and narrative and connection and meaning in the middle. There’s no single composer, no solitary musical genius. Instead, there are billions of musical geniuses out there, all creating this beautiful anarchy of sound.

We should care for that reason as well. It’s harder to encode that in a piece of policy legislation.

LISTEN: A meadow in Tennessee. [“In the murmurs of cells and the voices of animals, we hear solar energy refracted into sound,” Haskell writes in his book. “We are acoustic conduits for plant-snared light as its escapes to air.”]

Neel Dhanesha

What can we do to avoid the sensory extinction crisis?

David George Haskell

We can become more attuned to the soundscape of our own worlds. Listen to our neighborhoods and ask, “What is broken here, and what might I do individually or collectively to fix [it]?” There’s nothing like sitting down with a room of people and hearing the diversity of voices and perspectives and trying to work through that as a lesson in the meanings of political engagement.

Because we live in a globalized world economy, we need to be in solidarity with people working in their local environments elsewhere. We need to engage at the regional, national, and international levels by voting. The soundscapes of the oceans and tropical forests, which are in a particular crisis now, are affected by our political structures.

We also need to consider the soundscapes of our cities. In general, mainstream environmental groups have neglected where most people live, and where a lot of other species live next to humans, which is in cities. The reorientation of the environmental movement toward environmental justice in cities is part of what we need to be working toward.

Audio courtesy of David George Haskell; more sounds from the book can be found on his website.

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