The History and Future
of the Human Population
Prudent men should judge of future events by what has taken place in the past, and what is taking place in the present.
--Miguel de Cervantes (1547-1616), Persiles and Sigismunda
We shall see finally appear the miracle of an animal society, a complete and definitive ant-heap.
-- Paul Valéry ( 1871-1945)
The first small population of human beings probably appeared on Earth more than 2 million years ago on the continent of Africa. Since then, the human population has spread out to occupy virtually the entire land surface of the planet. And in the past century or two it has exploded in numbers. Today roughly between 4 and 5 percent of all the people who have ever lived inhabit Earth -- some 4 billion.1
This chapter recounts the history of population growth and explores its projected course in the future, especially the next century or so. Principles of human population dynamics (demography) are also presented here, with a view to explaining the present predicament of humanity and how the current demographic situation shapes the future and limits social options. Population size and growth have profound, if seldom noticed, effects on the course of events, and this is likely to be even more true in the future than it has been in the past.
Since there are no substantial historical data on which to base estimates of population size and changes before 1650, estimates must be based on circumstantial evi-____________________