There is no single African religion, as practices and beliefs varied widely across different regions and ethnic groups. Most African religions were oral traditions that incorporated belief in a supreme deity or high god, lesser spirits that could help or harm humans, and the active involvement of ancestors. Rituals and rites of passage marked important life events, and religious specialists like healers and diviners played important roles. While some North African regions integrated Greek, Roman and later Christian influences, the spread of Christianity and Islam more widely in Africa has changed and sometimes conflicted with traditional religious practices.