Reconstruction of a population

The history of human populations is the subject of historic demography. Ancient sources offer but very few statistically useful figures. Demography provides us with the mathematical tools and historic demography with the comparative material that enable us to arrive at some demographic reconstructions. Every population answers to some general rules. Even if our sparse sources barely allow us to describe any ancient population in some detail, we can at least indicate within which parameters those populations will have developed. Exactitude is beyond bounds: human fertility and life expectancy are influenced by many factors, such as the environment, food and water supply, hygiene and the prevalence of disease, housing, the duration of breast feeding, the norms or laws concerning marriage age, birth control, abortion and infanticide, and so on. For most times and places, the sources do not inform us about some or all of these factors. Also, migration is always a distorting factor when a population is reconstructed on the basis of supposedly general patterns, at least when one is interested in the size and the development of the population of an individual region or settlement. The same applies to the relatively short-term effects of war, famine, epidemic disease, and natural disasters.

Assuming that the societies of antiquity are comparable to other pre-industrial societies—and there is no reason to think otherwise—a high mortality rate of about 40 per thousand would have been compensated by a high birth rate (about 40 to 45 per thousand). The annual growth of the population would then have been between 0% and 0.5%. A growth rate of 0.5% is quite considerable: if this continues year after year, the cumulative effect means that a population will double in 140 years. It seems likely that for most of the time the ancient world did not keep up such growth rates for long.

If the preceding pattern is about right, it follows that almost a third of all children will die during their first year, and over half of all children before reaching the age of 15. Of every 100 newborn, 40 could expect to reach the age of 25, and 25 the age of 50. The high mortality rates should thus be in large part attributed to infant mortality. The life expectancy at birth is a mere 25 years, but the life expectancy at age 5 is 40 years. The age division of ancient societies must have looked like a pyramid with a wide base and narrow top: 40% to 45% of the population was under the age of 18, and the mean age was between 25 and 30. This was no ageing population, which of course does not mean that the ancient world did not have any experience with old age: in antiquity, some people became old or even very old; but the old were a very small minority in a world teeming with children.

The high mortality in the early years ensures that half or more of the newborn will never reach sexual maturity. If a population wants to reproduce under such conditions, every woman who does reach her fertile period should have five or six pregnancies. If we combine this fact and the supposition that in most pre-industrial societies breast feeding continued for long after birth, up to three years, during which time the mother could not become pregnant, we are forced to conclude that the age of marriage for girls was very low to take maximum advantage of the reproductive years. Indeed, ages of 12 to 18 years are mentioned in the sources from several different societies. A mean of five or six pregnancies is then possible (which does not mean that people have families consisting of five or six children: we have to subtract infant mortality).

The high mortality rates in antiquity meant that there was enormous social pressure on individuals to marry and produce children. To beget and bear children was the duty of every member of the community, advocated as the greatest blessing that the gods could bestow on humankind. It is no surprise that movements or ideologies that propagate celibacy and childlessness were unknown, until such a movement arose in India sometime before 500 BC. But also there the ideals preached never caught on with the population at large. When comparable ideas appeared later in the Mediterranean world, these met with strong resistance, as utterly foreign to ancient civil culture. In the early first millennium BC, asceticism was not preached anywhere. Indeed, religion was in large part occupied with ensuring the fertility of humans, beast, and crops.