Sapiens and Homo Deus: The E-book Collection: A Brief History of Humankind and A Brief History of Tomorrow

by Yuval Noah Harari

Bats, for example, experience the world through echolocation. They emit a very rapid stream of high-frequency chirps, well beyond the range of the human ear. They then detect and interpret the returning echoes to build a picture of the world. That picture is so detailed and accurate that bats can fly quickly between trees and buildings, chase and capture moths and mosquitoes, and all the while evade owls and other predators. Bats live in a world of echoes. Just as in the human world every object has a characteristic shape and colour, so in the bat world every object has its echo-pattern. A bat can distinguish between a tasty moth species and a poisonous moth species by the different echoes bouncing back from their delicate wings. Some edible moth species try to protect themselves by evolving an echo-pattern similar to that of a poisonous species. Others have evolved an even more remarkable ability to deflect the waves of the bat radar, so like stealth bombers they can fly around without the bat knowing they are there. The world of echolocation is as complex and stormy as our familiar world of sound and sight, but we are completely oblivious to it.