The sensory universes we cannot imagine

The German biologist Jakob von Uexküll introduced the idea of the umwelt: the sensory bubble that every creature inhabits, made up of only those signals its nervous system can detect. A tick waiting on a branch for years, triggered only by the warmth and smell of mammalian blood, lives in a radically different world from the fox passing beneath it. Ed Yong's 2022 book is an extended, joyful investigation of what that means.

Yong, a science writer for The Atlantic and winner of the Pulitzer Prize, moves through the animal kingdom with remarkable range. He explains how the star-nosed mole navigates almost entirely by touch, how mantis shrimp have sixteen types of colour receptor compared to our three, and how elephants communicate through vibrations in the ground detected by their feet.

The chapter on echolocation — how bats and dolphins build three-dimensional images of the world from reflected sound — is particularly striking. These animals are not using a crude backup system; echolocation gives bats the ability to detect an object the width of a human hair in total darkness while flying at speed.

Yong is careful not to claim that one umwelt is richer than another. A dog's olfactory world, processing some three hundred million scent receptors to our six million, may be as textured and detailed as anything we experience visually. The book is a sustained exercise in epistemic humility.

An Immense World won the Royal Society Science Book Prize in 2023. Its lasting effect on many readers is a practical one: you look at animals differently afterwards, knowing that they are not pale versions of human experience but inhabitants of entire worlds you will never enter.