Early on in this magnificent investigation of animals’ sensory worlds, Ed Yong dismisses attempts to “childishly” rank animal senses compared to our own, or create new human tools based on animal senses. “Animals are not just stand-ins for humans or fodder for brain-storming sessions,” he writes, and then quotes writer Henry Beston, “They are other nations, caught with ourselves in the net of life and time, fellow prisoners of the splendour and travail of the earth”. Although he can’t avoid either entirely in this field, I suspect that it’s just such approaches that have turned me ever so slightly off the topic in the past. Animal senses should be profoundly fascinating in their own right — who hasn’t wanted to slip into another creature’s experience? — and Yong at last gives them the popular treatment they deserve.
The early 20th Century German biologist Jacob von Uexküll conceived of an animal’s perceptual world as its Umwelt. Although humans and other lifeforms are perpetually bathed in potential information coming from the universe and each other, “every animal can only tap a small fraction of reality’s fullness”. That potential information comes in the form of stimuli — light, chemicals, vibrations, heat and more — which are picked up by specialised cells known as receptors. These transmit a nerve impulse to sensory organs, which in turn finally convert them into useful information. In a system with so many parts, you begin to comprehend how difficult it might be to understand another animal’s experience. Yong describes the Umwelt as like the windows of a house. “The human’s house might be bigger than the tick’s,” he writes, “With more windows overlooking a wider garden, but we are still stuck inside one, looking out … it is all that we know, and so we easily mistake it for all there is to know.”
Those limitations pose problems for the scientists studying senses — it took a while, for instance, for humans to figure out that when small bats opened their mouths they weren’t baring their teeth but emitting the beyond-human-hearing clicks that they use for echolocation. But they also provide a certain thrill. “Stepping between Umwelten … is like setting foot on an alien planet,” Yong writes. And so, we embark on an intergalactic tour of those planets. Yong starts with smell and taste, or rather the detection of chemicals, the oldest and most universal of animal senses. He moves on through sight, colour vision, hearing and echolocation, various forms of touch, and finally onto those two very weird animal senses (for humans), electroreception and magnetoreception. It’s fun and fascinating, until you get to a disturbing and rather poignant chapter on pain. Disturbing because the only way to study pain is to subject animals to it, and poignant because who hasn’t dreamed of having the superpower of not experiencing it (a superpower that would be highly debilitating and quite dangerous as it turns out. Pain tells us all sorts of important and useful things about the world).
That poignancy exists throughout An Immense World. There’s something quite moving about these scientists’s efforts to get inside the heads (or wherever it is they keep they their nervous systems) of these animals; this is, after all, a science dedicated to understanding what it’s like to live as someone else, and isn’t that one of the most important needs of our time, when we must come to care enough about nature to do something about the global environmental crises we’re amidst? It comes to a point when Yong discusses the ways in which we humans are polluting these sensory worlds with sound and light and no doubt many other human-made stimuli that we’re yet to properly understand. It’s bad enough for us. A third of people can no longer see the Milky Way. Two-thirds of people in Europe experience background noise equivalent to perpetual rainfall. “Sensory pollution,” Yong writes, “Is the pollution of disconnections. It detaches us from the cosmos.”
Page after page An Immense World induces a state of awe and wonder, but on an intimate scale, rather than the “canyons and mountains” where people have typically sought such feelings in nature. I could cite something from almost any paragraph, but instead I’ll mention just one, the colour vision of mantis shrimps, who have “the strangest eyes on the planet” and are also hilarious research subjects because they punch everything (oh alright, I have to mention the tiger wandering spider, which has touch so sensitive it can catch flies in the dark in mid air). Unlike humans which have three types of colour receptors, mantis shrimps have at least 12. Because each additional receptor adds a new dimension to their vision (birds, with four receptors, might be able distinguish between hundreds of millions of colours, compared to the million or so that we can see), theoretically mantis shrimps should be able to see untold trillions of colours. But, even more bizarrely, they’re really bad at distinguishing colour. Because of their structure of their eyes, they may simply scan their environment and produce something like a barcode that tells them all they need to know.
Yong does a very fine job of explaining technical concepts without reducing them, and strikes an excellent balance between detail and narrative (a multitude of footnotes entertain and expand throughout). This is quite a long, rich book, but light on its feet. It’s like throwing open a window.
Gay rating: 1/5 for inclusion of gender-diverse scientists.