Fig. 1. Daily consumption of energy per capita was calculated for 6 stages in
human development. Primitive people (East Africa about 1,000,000 years ago),
without the use of fire, had only the energy of the food they ate. Hunting people
(Europe about 100,000 years ago) had more food and also burned wood for heat
and cooking. Primitive agriculturists (Fertile Crescent in 5000 BCE) were
growing crops and had gained energy by putting animals to work. Advanced
agriculturists (northwestern Europe in AD 1400) had some coal for heating,
some water power, wind power, and animal transport. Industrial people
(in England in 1875) had the steam engine. Today technological people
(in the United States) consume an average of 243 kilocalories per person per day,
much of it in form of electricity (hatched area). Food is divided into
plant foods (far left) and foods fed to animals.
[After E. Cook, The Flow of Energy in an Industrial Society.
Copyright © 1971 by Scientific American, Inc. All rights reserved.]