Religion in Africa is very diverse, with traditional indigenous religions varying widely across the continent. Indigenous religions were integrated into everyday life and sought to explain concepts like order in the universe, good and evil. While most were polytheistic, they often involved belief in a major god and sub-deities as well as spirits that communicated between the physical and spiritual worlds. Islam and Christianity also have a strong presence in Africa due to spread by Arab traders and later European colonists starting in the 15th century. Today the continent exhibits a complex blend of traditional, Islamic and Christian religious traditions.