by Captivating History (Author) How two worlds became one. In this book, you will understand how Christopher Columbus proposed something new: reaching the riches of the East Indies by sailing west from Europe. The rulers of Spain agreed to support his risky venture, and he sailed off in 1492. He unexpectedly ran into two continents nobody in Europe knew about. He didn't discover the continents; that had been done centuries before. Discover how the Old World of Eurasia and Africa began a monumentally important exchange of people, ideas, crops, animals, and diseases that changed history and humanity forever. This extended stitching together of the two hemispheres is called the Columbian Exchange.