With all these states being linked through trade routes like the Silk Roads, the Indian Ocean trade, and the trans-Saharan trade, lots of people were moving around and intermingling
First domesticated in Southeast Asia, introduced to Africa through merchants crossing the Indian Ocean, flourished in the lush rainforests of sub-Saharan Africa, expanded the diets of the people and led to population growth
Drought-resistant grain of rice introduced to China from the Champa Kingdom in Vietnam, matured quickly and could be harvested more than once a season, led to a population explosion in China
Introduced by Muslim traders into Europe via the Mediterranean trade routes, spread throughout Europe and North Africa, led to more variation in diets and better health