Before the Columbian Exchange, which was never seen in Europe ?

When Christopher Columbus and his men came to the Americas over 500 years ago, they brought horses, chickens, and wheat bread from Europe. The Native Americans had never seen any of those things before. The Europeans had never seen the potatoes, peanuts, tomatoes, cocoa, or corn grown by the Native Americans.

which statement explains one of the reasons world war 1 was so much more destructive than earlier conflicts