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By the first millennium AD, the global population had grown to approximately 125 million. This growth continued through the centuries, albeit with setbacks from widespread epidemics, wars, and famines. The shift towards urbanization and medical advancements sparked a demographic transition, which fundamentally changed human reproductive patterns and mortality rates.
The Stages of Demographic Transition
The demographic transition model outlines various stages through which societies evolve in terms of birth and death rates:
Stage 1: High birth and death rates lead to a stable population.
Stage 2: Improvements in medical care and sanitation result in lowered death rates while birth rates remain high, leading to rapid population growth.