Columbian ExchangeAbout 200 million years ago, there was a large continent called Pangea. They believed that this landmass was beginning to break apart. They believed that the Atlantic Ocean had formed, separating Africa and Eurasia from the Americas. Over the next millions of years, plants and animals changed and became separate biological worlds. It wasn't until Christopher Columbus and his crew sailed to the Americas in October 1492 that they began to interact with each other. Europeans brought diseases to the Americas, such as smallpox and measles. The original descendants did not bring the diseases because they traveled in the cold and had no pets. Many of these diseases were caused by domestic animals. At the time, people in Afro-Eurasia had developed immunity to these diseases. Native Americans did not have these immunities, which is why 90% of early Americans died between 1492 and 1650. Old World crops such as wheat, barley, rice, and turnips did not have crossed the Atlantic to the west. Some of the New World cultures that...