Energy in Our Future

Abstract

Proto-human creatures emerged upon the earth some two million years ago. For the greater part of their existence they lived much as did the other animals about them; they gathered edible plants and hunted other animals. Their primary need for energy was in the form of food to nourish their bodies and amounted to about 3000 Calories daily. The controlled use of fire, which greatly extended the variety of foods that could be eaten and the range of human habitation, increased per capita energy consumption to about 8000 Calories per day, corresponding to the heat that would be released by burning a little over 1 kilogram of coal per day or somewhat over 400 kilograms of coal each year. In view of the fact that the earth in its natural state could hardly support more than about ten million food-gatherers (1), the maximum consumption of energy by humans in preagricultural times probably amounted to no more than the equivalent of about four million tons of coal annually.