ABSTRACT
Earth’s population likely reached 1 billion only at the start of the nineteenth century in about 1804 – having risen slowly and irregularly from 6 million in the time of hunter-gatherers and 370 million at the end of the Great Plague of the fourteenth century. World population would then double to 2 billion in just 123 years to 1927. Through most of recorded human history, the majority of humans have engaged in agriculture. Levels of agricultural productivity have largely determined whether a society could support large numbers of bureaucrats or merchants or artisans. Of course, increased food supply only allowed the population to grow. Humans had to decide to take advantage of their higher incomes by having more children. Global population growth rates peaked in the 1960s. There was considerable concern at the time about a “population explosion.” Many feared that population would continue to expand exponentially beyond the planet’s ability to sustain it.
