By the 1st century CE, many of the city-states such as Mombasa, Malindi, and Zanzibar began to establish trading relations with Arabs. This led to increased economic growth of the Swahili states, the introduction of Islam, Arabic influences on the Swahili Bantu language, cultural diffusion, as well as the Swahili city-states becoming members of a larger trade network. Many historians had long believed that the city-states were established by Arab or Persian traders, but archaeological evidence has led scholars to recognise the city-states as an indigenous development which, though subjected to foreign influence due to trade, retained a Bantu cultural core.