Review: An Immense World by Ed Yong

A terrific read. This book truly changed how I think about senses, and, more generally, how animals perceive the world. In particular, this book taught me the concept of the umwelt, a German word that roughly means “environment” or “surroundings,” but in particular, it’s the environment or surroundings as perceived by that animal. The world a python perceives via its infrared senses is very different than the world a bat perceives via echolocation, which is different than the world a spider perceives through vibrations, and so on.

It’s like we all live in the same house, but each animal is locked in a different room, where it can see the outside world only through a unique set of windows, so each animal gets a totally different view on what’s out there. And this view of the world doesn’t appear to the animal as a part of the whole, but as the whole thing: the animal isn’t aware that anything else could possibly exist out there, beyond its unique set of senses.

I found it remarkable to consider that there is an entire world out there that we can’t detect with our natural senses, and how that’s true for every animal, which means we all live in our own little worlds (our own umwelten). And I can’t help but wonder how many animals try to communicate with us in ways we just can’t perceive. And that’s for animals that evolved on the same planet as us; I can’t even imagine how different it must be if we ever come across aliens. Maybe we already have, and just couldn’t perceive them.

The book is full of examples of all the different types of animal senses, some of which I had heard of, and some I couldn’t even imagine. I found reading through all these examples created a genuine sense of wonder in me, and an appreciation for the diversity of life, and the power of evolution.

Here are just a few examples:

• There is a type of fly that have extraordinarily fast vision and reflexes. They can respond to visual stimuli in < 30 ms, whereas for humans, it takes longer than that just for an image to be absorbed by the retina, after which, we spend ~10x as long sending the image to the brain, processing the image, deciding what to do, and sending a signal back to the muscles to act. Moreover, whereas for humans, a flickering light starts to look more or less continuous at 60 hz (flickering 60 times per second)—which, not coincidentally, is used as the refresh rate for most monitors—these flies can detect flickering at well above 350 hz. That means that, to them, our movies look like slide shows, our attempts at boxing look like Tai Chi, and any attempt to swat such a fly, to them, will feel like you’re moving in slow motion. But there’s a funny twist here too: you can actually catch these flies by moving extremely slowly, because then, to the flies, you blend into the background, and they can hardly perceive you at all.

• You’ve probably heard that blue whale songs can carry across thousands of miles. It turns out that elephants can make and detect infrasonic sounds (those below the frequency of human hearing) that carry over great distances too. And mice, rats, and many other rodents can make and detect ultrasonic sounds (those above the frequency of human hearing). So all these years, it’s possible that mice and elephants have been trying to communicate with us, and getting frustrated because we never seem to respond!

• You’ve probably also heard that some aquatic animals, such as some eels and fish, can produce electric fields. What you might not have heard is that they can use these fields not only to attack others, but also to sense the world around them (“electroreception”). Although electric fields only work over short distances, unlike sound and sight, electric fields are not distorted by water or water currents, so they provide an extremely accurate view of the world around these fish. Moreover, some fish can detect other living creatures even in pitch black, totally silent conditions, because all living animals produce some degree of bioelectric fields, impedance, resistance, etc, that can be readily detected using an electric field.

• All senses must distinguish between external and internal events: e.g., when detecting something in your vision, is that because something moved in the external world, or because you moved your own eye? Did something just touch your hand or did you just move your hand to touch something? In either case, the stimuli going into the sensors can be exactly the same, so for the animal to distinguish these events, it must have some awareness of a “self”. Perhaps this is why we have a “self” in the first place!

• We’ve polluted our world in so many ways, not only in the literal sense (land fills, industrial waste, global warming, etc), but also in terms of polluting the senses: in particular, light pollution, and sound pollution. The level of ambient noise in many cities is equivalent to living in a constant rainstorm, 24 hours per day; the level of light pollution means millions of humans around the world can’t see the stars at night; the level of light pollution also interferes with some nighttime pollinating insects, which leads to significant lower pollination rates, and therefore, crop yields; and so on. This is bad for humans and bad for animals. This made me deeply appreciate living in a quiet part of the world, and perhaps an awareness of how we pollute the senses may help us think differently about how to build our world in the future.

The book is full of dozens and dozens of other remarkable examples: the astonishing accuracy of echolocation in bats and dolphins; the ability of birds to perceive magnetic fields; the 360-degree field of vision of mallard ducks; the ability of spiders and bees to detect electric fields with the little hairs on their bodies; the ability of robins to sing pitches outside the range of human hearing, so the beautiful songs we hear are only a part of the entire performance; and so on.

It’s a delightful read that I’d recommend to just about everyone.

I’ll close with a few of my favorite quotes from the book:

“Earth teems with sights and textures, sounds and vibrations, smells and tastes, electric and magnetic fields. But every animal can only tap into a small fraction of realities fullness. Each is enclosed within its own unique sensory bubble, perceiving but a tiny silver of an immense world.”

“The umwelt concept can feel restrictive, because it implies that every creature is trapped within the house of its senses, but to me, the idea is wonderfully expansive. It tells us that all is not as it seems, and that everything we experience is but a filtered version of everything that we could experience. It reminds us that there is light in darkness, noise in silence, richness in nothingness. It hints at flickers of the unfamiliar in the familiar, of the extraordinary in the everyday, of magnificence in mundanity.”

“A moth will never know what a zebra finch hears in its song, a zebra finch will never feel the electric buzz of a black ghost knifefish, a knifefish will never see through the eyes of a mantis shrimp, a mantis shrimp will never smell the way a dog can, and a dog will never understand what it is to be a bat. We will never fully do any of these things either, but we are the only animal that can try.”

“A scientist’s data are influenced by the questions she asks, which are steered by her imagination, which is delimited by her senses. The boundaries of our own Umwelt corral our ability to understand the Umwelten of others.”

“I find these connections profound, in a way that makes me think differently about the act of sensing itself. Sensing can feel passive, as if eyes and other sense organs were intake valves through which animals absorb and receive the stimuli around them. But over time, the simple act of seeing recolors the world. Guided by evolution, eyes are living paintbrushes. Flowers, frogs, fish, feathers, and fruit all show that sight affects what is seen, and that much of what we find beautiful in nature has been shaped by the vision of our fellow animals. Beauty is not only in the eye of the beholder. It arises because of that eye.”

Rating: 5 stars