Animals face a variety of problems. In addition to attacks by predators, they often have to survive harsh climates and shortages of food and drink. They react instinctively with a corresponding variety of solutions. Salient responses to bitter winters, scorching summers, and lack of food and drink include winter sleep, summer sleep, and migration. Although humans face the same survival problems, they have not evolved these particular reaction patterns. In common with most animals, humans living near the poles do not sleep all day in dark winters, and those living near the equator do not to sleep all day in blistering-hot summers. And almost all humans are reluctant to migrate permanently or to follow flocks of birds in spring and fall on their way to more comfortable places for the oncoming winter or summer. Indeed, unlike our distant ancestors in hunting and gathering societies, we tend to stay where we are, and that seems convenient. But in a hardening climate we are in danger.

In harsh climates, humans must ceaselessly solve problems of extreme cold or heat, shrinking food and drink supplies, and lurking diseases. In response, they have invented a tool no animal action ever can compete with. Its miraculous power can solve a fantastic variety of climatic, nutritional, and health problems. What's more, its wondrous achievements are in no way tied to a specific ethnic group, a particular geographic area, or a certain period in time.