World population growth from settlement of the continents to future population size is broadly traced in this work. Population growth has accelerated greatly in the past two centuries and especially since 1950. The first billion was reached only in 1850, while the fifth billion, in 1986, required only 11 years. Past population growth was slow, irregular, and variable from continent to continent. Population estimates for prehistory have a margin of error of around 50%. Modern man first appeared in Africa or possibly the Middle East around 100,000 BC. The three great centers of population in China, India, and the Middle East and Mediterranean area developed during the Neolithic Revolution and have maintained their importance. At least 500,000 years ago, humans began using fire and clothing to escape the limits of their biotype and geographic area of origin. The peopling of the continents was not achieved by massive displacement of surplus population, but by movement of small groups into empty space where they proliferated. World population was an estimated 460-510 million in 1500, with probably 135 million in China, 95 million in India, and 80 million in Europe. The balance between fertility and mortality postulated by transition theory has not occurred in Europe. World population is projected to increase from 2.5 billion to 6 billion between 1950 and 2000, with 61% in Asia, 12% in Africa, 9% in Latin America, and 5% in Europe. The world rate of population growth is still about 1.4% annually. The demographic explosion will have been a transitory episode in human history, but revolutionary in its impact.