Christianity in the 2nd century was largely the time of the Apostolic Fathers who were the students of the apostles of Jesus, though there is some overlap as John the Apostle may have survived into the 2nd century and Clement of Rome is said to have died at the end of the 1st century. While the Christian church was centered in Jerusalem in the 1st century, it became decentralized in the 2nd century. The 2nd century was also the time of several people who were later declared to be major heretics, such as Marcion, Valentinius, and Montanus.