The European "discovery" of the Americas led to several things. One was the conquest and settlement of the Americas by people of European ancestry, a process that, while not completed until the nineteenth century, was still a profoundly important event in world history. This process was only possible because of the destruction of the indigenous societies that lived in the Americas before contact with Europeans. This, in fact, was the second major effect of the discovery--Native peoples were devastated by European diseases such as smallpox and typhus. This represented one of the most significant demographic catastrophes in human history. Another effect is what was named the "Columbian Exchange" by one historian. Plants, animals, and, as mentioned above, diseases that had been separated by millions of years of evolution came in contact with each other. Animals from Eurasia and Africa that were introduced to the Americas included horses, chickens, cattle, rats, mosquitoes, and sheep. Plants like wheat, sugarcane, and even common weeds like chickweed and dandelions also flourished in the Americas. Corn and potatoes went the other way into Europe. Still another effect was that extracting the wealth of the Americas played a role in enabling the development of powerful European nation-states, starting with Spain and including England and France. The influx of wealth to Europe is often pointed to as a factor in the development of capitalism as well. So there are many profound effects--both short and long-term--of the collision of the Old and New Worlds that began in 1492.