Maize and cassava, introduced by the Portuguese from South America in the 16th century, gradually replaced sorghum and millet as Africa's most important food crops. Spanish colonizers of the 16th-century introduced new staple crops to Asia from the Americas, including maize and sweet potatoes, and thereby contributed to population growth in Asia. On a larger scale, the introduction of potatoes and maize to the Old World "resulted in caloric and nutritional improvements over previously existing staples" throughout the Eurasian landmass, enabling more varied and abundant food production.