Converting to rice: urbanization, Islamization and crops on Pemba Island, Tanzania, AD 700-1500

Prior to Arab and European imperialism, the farmers of eastern Africa's Swahili coast engaged in a mixed economy, including fishing, animal husbandry and trade in the Indian Ocean's early global economy. This trade network also exposed eastern Africans to new Asian foodways. Botanical data from archaeological sites on northern Pemba Island, Tanzania, show that ancient Pembans first relied heavily on pearl millet, but subsequently became specialized producers of cotton and the Asian crops rice and coconut during the growth of the trading town of Chwaka. This turn towards Asian foodways, particularly rice, was part of a broader alignment with Indian Ocean cultures during a period of urbanization and Islamization along Africa's eastern coast between the eleventh and the fifteenth centuries. Rice specialization was risky due to the constraints of suitable land, rainfall, and labour supply, and it is likely that social and political rewards compelled this agricultural innovation.