In the southern coastal region, kinship networks tended to be more fluid and symbolic and could therefore exert less of an impact on the way individuals interacted. Key factors were the area's extremely hot and humid climate especially during the summer - and trade, which encouraged the migration of coastal peoples and communities throughout the Persian Gulf. Coastal communities, which were cosmopolitan and multicultural, tended to exhibit greater racial and religious tolerance (Mojtahed-Zadeh, 2003, p. 67). Peoples of African descent, therefore, tended to reside in non-hierarchical communities that practised mostly exogamous marital arrangements. Today, all the inhabitants of southern Iran, including descendants of Africans, are referred to as Bandaris (the people of the port) and those who remain visibly distinctive are known as siyaban-i janub (the blacks of the south). These terms are commonly used in popular culture, films and songs, highlighting their African origin. Ironically, many Iranians are wont to attribute the prevalence of either lighter or darker complexions to climatic variations, namely, darker skin to the south and fairer skin to the cooler north.