How has the world's population increased so much in 500 years

In the year of 1500 there were 450 million people in the world. Today there are more than 7 billion. Did people decide suddenly to breed like rats or what?

The main contribution to the increase in population of humans on this planet is the introduction of improved medicine and better hygiene. Over the past few hundreds years there has been a massive breakthrough in medicinal biology, we have found a ton of cures for diseases, we now understand the biology of a cell and what causes illnesses and diseases and how these diseases can be passed on through water, food, surroundings etc. There are, especially in more developed countries, a much lower infant mortality rate, due to hospitals and the endeavour of scientists in the medicine field.

Hope I've helped!