The Pre Columbian Exchange

The Columbian Exchange is the exchange of plants, animals and microorganisms between the Eastern and Western hemisphere that occurred after the voyage of Columbus.

Were there previous exchanges? Did the Vikings bring diseases to the new world when they arrived? When the Eskimos and Norse met in Greenland, did they exchange diseases and bring them back to where they started. Apparently not.

However, when the first ancestors of the "Native Americans" arrived across the Bering Straits from Asia, they surely started a major transformation of the Americas. Not only did they become the most important keystone species in the Americas, the Native Americans terraformed the continents. They modified the environment using fire, supporting the growth of populations of animals that they wanted and hunting others, modifying the soils, and encouraging the growth of "useful" plants while discouraging "weedy" plants.

Agricultural terraces in Peru, like those created by pre-Columbian cultures