The human species first evolved about

Major changes in the human population first began in the 1700s. These changes occurred mainly in Europe, North America, and a few other places that became industrialized. First, death rates fell. Then, somewhat later, birth rates also fell. These changes in death and birth rates affected the rate of population growth and are referred to as the demographic transition.     The demographic transition is generally divided into four stages. In stage 1, birth and death rates were both high, so population growth was slow. In stage 2, death rates fell while birth rates remained high. Why did death... Show more

Major changes in the human population first began in the 1700s. These changes occurred mainly in Europe, North America, and a few other places that became industrialized. First, death rates fell. Then, somewhat later, birth rates also fell. These changes in death and birth rates affected the rate of population growth and are referred to as the demographic transition.    
The demographic transition is generally divided into four stages. In stage 1, birth and death rates were both high, so population growth was slow. In stage 2, death rates fell while birth rates remained high. Why did death rates fall? There were several reasons, including new scientific knowledge of the causes of disease. Water supplies were cleaned up, and sewage was disposed of more safely. Better farming techniques and machines increased the food supply and the distribution of food. For all these reasons, death rates fell, especially in children. Birth rates, on the other hand, remained high. This resulted in faster population growth.    
Before long, birth rates also started to fall. This was the beginning of stage 3 of the demographic transition. People started having fewer children because large families became too expensive. For example, with better farming machines, farm families no longer needed as many children to work in the fields. Laws were also passed that required children to go to school. They could no longer work and help support the family. Having many children became too costly. Eventually, birth rates fell to match death rates. As a result, population growth slowed down.    
When this occurred, stage 4 had been reached.    
Just as they did in Europe and North America, death rates have fallen throughout the world. No country today remains in stage 1 of the demographic transition. However, birth rates are still high in many of the poorest countries of the world. Many populations seem to be stuck in stage 2 of the demographic transition. They have high population growth rates because low death rates are not matched by equally low birth rates. Whether these countries will ever reach stage 4 and attain very low rates of population growth is uncertain.    

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