 Islam is the religion of the region's biggest ethnic groups by population.Islamic rules on livelihood, values, dress and practices had a profound effect on the populations and cultures in their predominant areas, so much so that the concept of tribalism is less observed by Islamized groups like the Mande, Wolof, Hausa, Fula and Songhai, than they are by non-Islamized groups.Ethnic intermarriage and shared cultural icons are established through a superseded commonality of belief or community, known as ummah.