Di Carlo La Vecchia-3^D- 12 October 1492: Christopher Columbus discovered the America. It was the beginning of the modern era, a period of explorations, discoveries and progress but also of unpeaceful colonisations and bloody genocides. In fact, when the Europeans came to the New World, it wasn’t uninhabited: tens of millions of natives were populating those lands, and in less than a century the numbers reduced of around 90%. The civilizations that existed in America before the arrival of the Europeans weren’t very advanced technologically, but were very populous and prosperous. Examples of these populations are the Maya, the Aztecs and the Incas. They were very ancient civilizations (the Maya first established around 2600 BC). The Aztecs and the Incas were organized in huge hierarchical empires, whilethe Maya were divided in many independent city-states which were mainly inhabited by the priests. They didn’t know iron and the wheel and their agriculture was very rudimentary, but they excelled in other aspects.The Maya had a very advanced astronomical and mathematical knowledge: they knew and used the zero and their calendar and astronomical studies were even more accurate than the European ones.The Aztecs were very urbanized,they built advanced palaces and their capital Tenochtitlan was one of the greatest and most populated cities of the world (in Europe, for example, only Paris, Venice and Constantinople could rival with it).The Incas were clever engineers who built a complex system of roads, bridges and tunnels that reached the whole empire; unlike Mayas and Aztecs, they didn’t know to write but used some strings called quipu to communicate and record calculations.