Population history

Demographic history is the reconstructed record of human population in the past. Given the lack of population records prior to the 1950s, there are many gaps in our record of demographic history. Historical demographers must make do with estimates. models and extrapolations. For the methodology, see Historical demography

Estimating the ancestral population of anatomically modern humans, Colin McEvedy and chose bounds based on gorilla and chimpanzee population densities of 1/km² and 3-4/km², respectively, then assumed that as Homo erectus moved up the food chain, they lost an order of magnitude in density. With a habitat of 68 million km² ("the Old World south of latitude 50° north, minus Australia"), Homo erectus could have numbered around 1.7 million individuals. After being replaced by Homo sapiens and moving into the New World and de-glaciated territory, by 10,000 BC world population was approaching four million people. McEvedy and Jones argue that, after populating the maximum available range, this was the limit of our food-gathering ancestors, with further population growth requiring food-producing activities.

The initial population "upswing" began around 5000 BC. Global population gained 50% in the 5th millennium BC, and 100% each millennium until 1000 BC, reaching 50 million people. After the beginning of the Iron Age, growth rate reached its peak with a doubling time of 500 years. However, growth slackened between 500 BC and 1 AD, before ceasing around 200 AD. This "primary cycle" was, at this time in history, confined to Europe, North Africa, and mainland Asia. McEvedy and Jones describe a secondary, "medieval cycle" being led by feudal Europe and Song China from around 900 AD.

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