According to Vansina small kingdoms and Kongo principalities appeared in the current region by the 1200 CE, but documented history of this period of Kongo people if it existed has not survived into the modern era. Detailed and copious description about the Kongo people who lived next to the Atlantic ports of the region, as a sophisticated culture, language and infrastructure, appear in the 15th century, written by the Portuguese explorers. Later anthropological work on the Kongo of the region come from the colonial era writers, particularly the French and Belgians (Loango, Vungu, and the Niari Valley), but this too is limited and does not exhaustively cover all of the Kongo people. The evidence suggests, states Vansina, that the Kongo people were advanced in their culture and socio-political systems with multiple kingdoms well before the arrival of first Portuguese ships in the late 15th century.