Various Shi’a communities have been identifiable since at least the eighth century. Among the principal features that distinguish Shi’a from Sunni tradition is the belief that a legitimate successor to leadership, called imam (pronounced eeMAAM), must be designated by his predecessor and belong to the family of the Prophet. According to ancient Shi’a belief, Muhammad did designate his cousin Ali, but Abu Bakr, Umar and Uthman managed to usurp power and prevent Ali from assuming his rightful place. Around the middle of the eighth century a split developed over who would be the seventh Imam. One group continued to pledge their loyalty to a man named Isma’il, who had just died, even though Isma’il’s father, the seventh Imam Ja’far, appointed a replacement when Isma’il died. The faction that stayed with Isma’il came to be called the Isma’ilis, or Seveners, since their line of Imams ended then. There are now at least two major branches of Seveners, one of which looks to the Aga Khan as its spiritual leader. The larger group of Shi’ites in the eighth century believed the legitimate line of Imams extended to a twelfth, and ended when that Imam went into concealment until his expected return at the end of time. Twelver Shi’ites are by far the majority community, constituting nearly all of Iran’s and more than half of Iraq’s people.