Assuming that if a man and a woman appeared on this planet earth about 5 lakh years ago (it is believed that man separated off from the animal kingdom a million years ago) and their progeny grew at an extremely low rate such as .0001 percent per year, today the world population would have been around 10²². Is this size not just unimaginable and unsustainable? Even a much lower growth rate as .00001 percent on sustained basis would yield an unsustainable figure for today. A growth rate of .001 produces a population of 1.03*10²² in just 50,000 years.

Population growth rate depends on three factors: fertility, mortality and migration. When we are discussing the world population trends we may ignore the component of migration. This implies that in the past, when population grew at an extremely slow rate, either the long term death rate was very high or the fertility could not keep pace with mortality. Reproduction rate was only as high as the death rate. The two rates may have fluctuated: when mortality rate was high, fertility was also high and when mortality was less, fertility was also less or this may have happened with a small time lag. Alternatively, fertility was high and in short terms population would rise but periodically epidemics and wars would destroy a great proportion of population and the population size would come down to initial levels. In both cases, the result is that for a long time the world population was stationary or growing at a very slow rate.

CAUSES OF SLOW GROWTH

We do not have the exact demographic information on ancient society. There are only projections and conjectural estimates. There are mere speculations about the rate of growth and fertility and mortality. Paleodemographers assume that ancient society had a long run tendency to remain stationary for various reasons. Hume (1977) suggested three reasons why ancient societies could not be more populated: