Imagine yourself as a star-nosed mole. You are about the size of a hamster, and you live most of your life underground in darkness. For this reason, you depend upon the eleven pairs of pink sensors that jut out from the front of your face. You depend upon them for everything: to sense the tunnels around you, the objects you encounter, the food before you. These sensations are nearly instantaneous, reaching the brain in about ten milliseconds. Imagine yourself rooting about in the dark, living by the pressure on the front of your face, forming a vision of the world entirely via touch.
We might be forgiven for assuming that other creatures perceive the world more or less as we do. But we would be mistaken. Our world is full of creatures with sensory organs so different from our own as to render their lives unimaginable to us. This is the premise of the philosopher Thomas Nagel’s groundbreaking essay “What Is It Like to Be a Bat?”: “In so far as I can imagine this (which is not very far), it tells me only what it would be like for me to behave as a bat behaves. But that is not the question. I want to know what it is like for a bat to be a bat.” If one’s perceptions constitute one’s sense of being in the world, then how could we possibly hope to imagine ourselves in the lives of those whose perceptions are nothing like our own?
In An Immense World, Ed Yong gives it a shot. Yong is a science writer at the Atlantic, where he has published some of the best reporting on the COVID-19 pandemic, but his background is in reporting about the nonhuman world. His first book, I Contain Multitudes, is on the subject of microbes, and he has published articles on endangered whales, malaria, mushroom parasites, and corals. In his new book, he takes on the vast subject of animal senses, attempting to synthesize hundreds of years of research into a tight 350 pages.
Yong is trying to tug readers beyond their own experience and intuitions into the deeply alien world of nonhuman lives. He begins his book with an account of the German zoologist Jakob von Uexküll’s concept of the Umwelt: environment, literally, but more “specifically the part of [an animal’s] surroundings that an animal can sense and experience—its perceptual world.” All animals perceive some things and do not perceive others. Consider the tick, which senses heat and skin odor but has no need to perceive color. Uexküll compared the Umwelt to a house whose many windows open onto a garden, and whose view of the garden depends on which windows open when, and onto what. “Each species is constrained in some ways,” Yong writes, “and liberated in others.”
As Yong shows, the animal kingdom is full of wildly diverse kinds of perception. Deep sea creatures evolved in a zone without sunlight and proceed largely according to the signals they gather from the movement of the water around them. Tiny insects hunt and communicate using vibrations on the surface of a leaf. Many animals see deep into the ultraviolet end of the color spectrum, perceiving patterns and colors invisible to the human eye. Cock-eyed squid have evolved two different kinds of eye, one to look upward for prey in downwelling sunlight, the other to search for bioluminescence below. Pit vipers have developed immensely sensitive nerve endings that can perceive changes in temperature of as little as .001°C, which enables them to hunt in the dark. The whiskers of harbor seals track fish by detecting invisible water trails.
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