AN IMMENSE WORLD
How animal senses reveal the hidden realms around us
By Ed Yong
Illustrated. 449 pages. Random house. $30.
A dolphin that echolocates a human in water can perceive not only the human’s outward shape, but also what is inside, including the skeleton and lungs. Tree frog embryos — nestled in their unhatched eggs — can detect the vibrations of an attacking predator and release an enzyme from their face that dissolves the shells they’re in, allowing them to escape and escape.
That I was surprised at so many moments while reading ‘An Immense World’, Ed Yong’s new book on animal senses, speaks to his exceptional gifts as a storyteller – although it may also say something regrettable about me. I marveled at those details because I thought they were strange; but it turns out that if I try to expand my perspective a little bit, they’re not that weird after all. One of Yong’s themes is that much of what we consider ‘extrasensory’ is ‘just sensory’. A term like ‘ultrasound’ is ‘an anthropocentric condition’. The upper frequency limit for the average human ear may be a meager 20 kilohertz, but most mammals can hear well into the ultrasonic range.
Yong offers these facts in a generous spirit, clearly aware that part of what will captivate readers is discovering how little of these facts many of us have known. I would have called the book “enlightening,” but Yong made me realize how much bias there is in an adjective like this; humans, as a species, are “so relentlessly visual” that light has come to symbolize safety, progress, knowledge, hope and good for us – and so we’ve lit up the planet to make it a more comfortable place for us, while making it is less habitable for others. Artificial light has been a fatal draw for young sea turtles, migrating songbirds and some insects, sending them to predators or disorienting them to exhaustion.
To understand this, we need to push the boundaries of our own ‘unique sensory bubble’ to find out what we can about how other species experience their environment. Yong’s book is funny and elegantly written, gracefully understated when it comes to slang, though he does introduce a helpful German word that he uses throughout: Umwelt† It means “environment,” but a little over a century ago, the Baltic-German zoologist Jakob von Uexküll used it to refer more specifically to that sensory bubble — an animal’s perceptual world.
The animals in Yong’s book are mostly non-human, but scientists are necessarily part of his story too. “A scientist’s explanation of other animals is determined by the data she collects, which is influenced by the questions she asks, which is guided by her imagination, which is delineated by her senses,” Yong writes. Human Umwelt will necessarily determine how we understand others Umwelten† “An Immense World” inevitably refers to the philosopher Thomas Nagel’s foundational essay on this struggle: “What’s it like to be a bat?”
But some people may be more open-minded than others. Some of the sensory biologists Yong meets are perceptually aberrant, see color differently or have trouble remembering familiar faces: “Perhaps people who experience the world in ways that are considered atypical,” he writes, “have an intuitive sense of the limits of typicality.”
“An Immense World” is organized by stimuli and their corresponding senses, starting with smell and taste and extending to the ability of some animals – birds, bumblebees – to detect the Earth’s magnetic field. When it comes to sight, there’s a tradeoff between sensitivity and resolution; humans tend to have extraordinary visual acuity during the day but have a much harder time seeing at night, while animals with better night vision don’t register the sharp images at a distance like we do. “Phrases always have a price,” Yong writes. “No animal can sense everything right.” The world overwhelms us with stimuli. Registering some of it is taxing enough; fully processing the continuous deluge of it would be overwhelming.
Yet an animal will use the various senses at its disposal to to make sense of the world around it. A mosquito is attracted to the heat of warm-blooded hosts, but will only attack if it smells carbon dioxide first – the sensation of heat without carbon dioxide is not a meal for a mosquito, but a sign of potential danger. A researcher tells Yong that protecting people from mosquitoes is a complicated undertaking, involving multiple senses at once; the little bug has “a plan B at every point”.
Such exchanges are an outlier in the book. Yong is not that interested in the well-known question of how the senses of animals can be used for human well-being; he wants us to try to understand how animals experience the world so that we can understand how animals experience the world. A mouse’s whiskers are for tapping, allowing it to scan the space around its head; what appears to be a fly’s chaotic flight path turns out to reflect the finely tuned thermometers of its antennae, steering it towards more comfortable temperatures. “Animals aren’t just stand-ins for humans or fodder for brainstorming sessions,” Yong writes. “They have value in themselves.”
If there is an advantage in trying to empathize with the experiences of others, it may be in the enormous difficulty of doing so; the boundaries of the sensory bubble of each species should serve as a reminder that each of us has just bought a piece of reality. Yong’s previous book, ‘I Contain Multitudes’, was an exploration of microbes and microbiomes; his writing for The Atlantic about the Covid-19 pandemic has often shown how response to the crisis was limited by our assumptions about the world and our place in it. Yong would like us to think more expansively — something humans, it turns out, are capable of doing.
Extensive thinking would help us realize that the true wonders of nature are not limited to some remote wilderness or other sublime landscape – what Yong calls ‘otherworldly splendor’. There is as much grandeur in the soil of a backyard as there is in the canyons of Zion. Recognizing the breadth of this immense world should awaken in us a sense of humility. We have to get over ourselves first.