Question: what was the single most important thing the spanish brought to the new world

title: New World
text: The label is also often used in agriculture . Africa , Asia , and Europe share a common agricultural history stemming from the Neolithic Revolution , and the same domesticated plants and animals spread through these three continents thousands of years ago , making them largely indistinct and useful to classify together as `` Old World '' . Common Old World crops ( e.g. , barley , lentils , oats , peas , rye , wheat ) , and domesticated animals ( e.g. , cattle , chickens , goats , horses , pigs , sheep ) did not exist in the Americas until they were introduced by post-Columbian contact in the 1490s ( see `` Columbian Exchange '' ) . Conversely , many common crops were originally domesticated in the Americas before they spread worldwide after Columbian contact , and are still often referred to as `` New World crops '' ; common beans ( phaseolus ) , maiz , and squash -- the `` three sisters '' -- as well as the avocado , tomato , and wide varieties of capsicum ( bell pepper , chili pepper , etc . ) , and the turkey were originally domesticated by pre-Columbian peoples in Mesoamerica , while agriculturalists in the Andean region of South America brought forth the cassava , peanut , potato , quinoa and domesticated animals like the alpaca , guinea pig and llama . Other famous New World crops include the cashew , cocoa , rubber , sunflower , tobacco , and vanilla , and fruits like the guava , papaya and pineapple . There are rare instances of overlap , e.g. , the calabash ( bottle - gourd ) , cotton , and yam , and the dog , are believed to have been domesticated separately in both the Old and New World , their early forms possibly brought along by Paleo - Indians from Asia during the last glacial period .