There is a belief among many denominations that the Apostles' positions were handed down to others: the view is commonly known as Apostolic Succession. This is a fundamental and essential part of the Roman Catholic Church's position, as their Nicolaitanistic clergy would have no justification without it. Likewise, many of the Protestant groups that came out of Rome (Lutheran, Presbyterian, Methodist, etc.) or split off (Episcopal, Eastern Orthodox, Anglican) teach a similar form of Apostolic Succession, though not as fiercely as the RCC.
To fully understand the quandary that modern "Christianity" is in requires a little digging into the history of the Body of Christ, or the Church. While the universal Body of Christ actually began at Pentecost, when the Disciples were empowered with the Holy Ghost, some groups teach that Christ founded His church on Peter, using Matthew 16:18;
"And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it."The only problem with that is that Jesus had just gotten done asking Peter who he thought Jesus was, to which question he responded, "Thou art the Christ, the Son of the living God." Now, Peter's name means little stone, but Jesus is the Rock of Ages and the Cornerstone, so Jesus building His church on Himself (a rock) makes much more sense than Him building it on Peter (a stone).
Anyhow, that's how the Church started: Peter was the first spokesman, and later Paul was the main instrument to spread the Gospel of Christ. The Gospel began to spread when the Jews started persecuting the Christians, and they moved away, taking their relatively new-found faith with them. Eventually the Gospel reached Rome, where Paul wound up getting executed by Nero. When the number of Christians became a large problem for the Roman government, they were persecuted with all the fury of the Roman legions, yet they continued to grow even more.
By 300 A.D., Emperor Constantine realized that they would never be able to root the Christians out, and as the saying goes, "If you can't beat them, join them"; he did exactly that. He "Baptized" his troops by marching them through the river, after which he had his armies wear crosses on their armor. He cited a vision in the sky, where a cross stood bearing the inscription: "In Vince Hoc," or "With this conquor." Many church elders warmly welcomed the respite from persecution, though some feared the new union between the government and the body of Christ. Constantine's new religion began incorporating many of the trappings of the former pagan worship, including polytheism, ornate worship services, temple prostitution and other godless, profane things, under the guise of "Christianity."
There were many people, however, that fled this new abomination, and eventually were persecuted as the unholy union of church and state began to overshadow Europe and the entire Roman Empire. In an effort to stifle the resistance to their religion, the Roman church forbad the common people to own or possess any portion of the Scriptures, or writings of the apostles or the Hebrew Old Testament. In this they thought to control the people, and keep them in ignorance to the abominations they were perpetrating in the name of Christ.
Between 393 and 419 A.D., different councils and synods had declared the "Canon" of the Bible, or which books were and were not Scriptural. The Roman church, using the idea of Apostolic Succession, declared that since Jesus gave Peter the keys of the Kingdom of God, that they still held those keys and also had the right to declare what was God's word.
By contrast, however, the Bible states that God's word is settled forever in Heaven, negating the necessity of a canon. Just because a group of men gets together and declares something to be so does not establish it, just as their refusal to accept something does not negate its existence. Therefore, to claim that the Roman Catholic Church is the authority on the written word of God, when God had already settled it in Heaven in eternity past, is preposterous to the highest degree. The Catholic church simply wanted to keep the people in darkness to the word of God (hence the "Dark Ages") so their "Indulgences" and "Penances" and "Priests," "Monks," "Nuns," "Friars," "Cardinals" and "Bishops" wouldn't be uncovered as fraudulent, unblibical, paganistic trash.
The grass withereth, the flower fadeth: but the word of our God shall stand for ever.