Pre-Industrial Revolution

About 15,000 ago (during the Holocene Epoch), humans were hunter-gatherers that thrived on predation. The mastery of fire equipped humans with powerful tool unavailable to other species. Humans used fire to ward off dangerous animals while hunting protein-rich food. Their diet was low caloric intake, which lead to low body fat, late menarche, and fertility at later age. Furthermore, Women collected food, resulting in vigorous exercise that lead to low body fat. In addition, as women collecting food, nursing women could not carry more than one infant at a time. Hence, a woman may only have a child every four years due to these restraints. Finally, the lack of food storage technology increased the frequency of famine as undernourished women could not conceive, carry fetus to term, or have successful childbirth. 

However, around 11,000 years ago, the warming of the climate resulted in the spread of agriculture across the world. Agriculture involves the domestication of plants and animals. It was discovered over ten times independently, in Holocene Epoch, throughout the world. The shift from forager to producer societies is known commonly as the Neolithic Revolution. With agriculture, birth rates increased rapidly. In fact, the population multiplied over 1200 times in 11,000 years. Agriculture allowed sedentary existence and reduced energy for carrying infants. In addition, the agricultural diet provided larger, more diverse amounts of high-calorie food. In addition, advent of agriculture was also met with better food storage. With this stable resource and increased trade, women were capable of reducing intervals between their births, thus increasing the birth rate of the world.

Figure 1: population explosion of Neolithic Demographic Transition

Figure 1 describes the population explosion of the Neolithic Demographic Transition. Before agriculture, the proportion of 5-to-19 year-old skeletons in cemeteries across Northern Hemisphere is approximately constant and remains around 0.23. However, after agriculture, there is significant larger proportion of 5-to-19 year-old skeletons in the cemetery. This suggests that there was much larger birth rate at this time, explaining the changes in population size.

While agriculture allowed birth rates to increase, the sedentary lifestyle also brought about larger death rates. Coupled with a sedentary village life, the population density within societies increased, thus caused increase in transmission of diseases. Also, there existed a lack of clean water as humans lived with waste. In addition, humans lived alongside their domesticated animals, which brought their own diseases. Children were most susceptible to these diseases, which included Cholera, diphtheria, measles, malaria, yellow fever, typhus, rotavirus, and coronavirus. The increase in juvenile deaths in Figure 1 can be attributed to these diseases. As a result, with extremely birth rates, this agricultural lifestyle resulted in high death rates. For the next 9,700 years, humans continued living in societies with high birth and death rates. During this period, the growth rate was less than 0.5% over 10,000 years. Over the years, humans improved at reducing disease, so the death rate edged down. The birth rate remained high as food remained bountiful. However, at the end of the 18^th century, a new demographic transition began.