The grossly stereotypical American Indian, like from the movies, riding the Great Plains with an eagle feather headdress and war paint, well he didn't exist before the Columbian Exchange because there were no horses for him to ride. And the introduction of horses allowed many Native Americans to abandon agriculture in favor of a nomadic lifestyle because riding around hunting buffalo made them far richer than farming ever had. Thanks Thought Bubble. But before animals and diseases completely reshaped the New World, it was New World plants that had the biggest effect on Eurasia. Sure, Europeans brought over some crops that we now grow here in the Americas, like wheat and grapes, both of which are necessary for Catholic Mass. But New World plants radically changed the lives of millions, maybe hundreds of millions, of Africans, Asians, and Europeans, specifically by making pizza possible. It was the greatest gift of all.