Why couldn't we truly talk about "World History" before the arrival of the Italian sailor to the new world? Please answer with a complete idea ASAP please it's for a test

Explanation:

Columbus himself had made that assumption. His discoveries posed for him, as for others, a problem of identification. It seemed to be a question not so much of giving names to new lands as of finding the proper old names, and the same was true of the things that the new lands contained. Cruising through the Caribbean, enchanted by the beauty and variety of what he saw, Columbus assumed that the strange plants and trees were strange only because he was insufficiently versed in the writings of men who did know them. "I am the saddest man in the world," he wrote, "because I do not recognize them."

im not sure on this one