Ancient Populations

If a single human being can subsist through hunting and harvesting crops in 10 km2 of exploitable area, or 2–3 people per surface of 100 km2 (or 0.01–2 people per square mile), agriculture has multiplied the number of people who can draw sustenance from the same areas. It is estimated that in the Neolithic Age, the density rose to 10 persons per 10 km2, ten times as much as before (see also Kander et al. 2014, 46).

The rise of civilizations has always been marked by population growth, which increases the complexity of societies. Population growth in terms of density and absolute numbers distinguished the great powers of ancient times. According to estimates, around 400 BC the complex of the Classical Greek city-states had 3 million inhabitants, which decreased with the loss of its strength and unity upon the death of Alexander the Great. Meanwhile, the Italian peninsula conquered by the Romans was in geopolitical rise with 4 million inhabitants. Its population reached 7 million at the beginning of the Christian era, when the Roman Empire lived on the tributes received from dozens of provinces, which enabled it to feed and maintain such a large number of citizens. The population of all of Europe was 31 million inhabitants at the time, always according to estimates. Egypt was the most populous province in the Roman Empire, with 7.5 million inhabitants in the first century AD, a number estimated to have grown to 10 million in the following century. According to Reinhard, Armengaud and Dupaquier, this was “thanks to improved irrigation systems” but, as Boserup would say, these systems might have had to be adopted precisely to accommodate the growing population. This dilemma could be solved only with a microhistorical analysis—if we had the relevant data. The number of Egyptians declined to around 3 million in the fourth century. The Roman Empire had 46 million subjects at its height, which, with its decline, was reduced by one quarter.

The Chinese empire, later the republic, has always been the most numerous politically united human group, starting from its unification under the Han dynasty two centuries before Christ.