Do you mean who wrote the gospels, acts, and apocalypses or, who wrote the early histories? Most of the authors of the canonical texts are attributed to four gospel writers and Paul/Saul of Tarsus, although scholars feel that some of the texts are attributions -- texts written by others and attributed to one of the canonical authors or disciples. For example, John 7:53 - 8:12 (the woman who committed adultery and was brought before Jesus) is one of the best known stories in the bible, but was not written by the author of John. From Erhman's "
Misquoting Jesus"
Quote:Despite the brilliance of the story, its captivating quality, and its inherent intrigue, there is one other enormous problem that it poses. As it turns out, it was not originally in the Gospel of John. In fact, it was not originally part of any of the Gospels. It was added by later scribes.
Another example is with the last twelve verses of Mark. Earlier texts have Mark ending after 16:8. The ending was modified at a later time and 16:9 - 16:20 was added. Some versions of the bible end after 16:8, some use a shorter ending, some amend 16:9 - 16:20 with or without a 'doubtful' after 16:8, etc.
There are apparently thousands of examples in the early texts, both canonical and extra-canonical that were modified over time. Some modifications were intentional to alter the tone of the story, some were inadvertent mistakes by scribes as they made copies of the texts. There are also entire gospels (the Gospel of Peter, for example) that were attributed to a particular author or disciple to give the story credence, but are pure forgeries. At least four of Paul's canonical letters were written by someone else (1-2 Timothy, Titus, Ephesians, and possibly Colossians and 2 Thessalonians), as were some of his letters that did not become canon. It is also thought that some of Paul's authentic letters were modified prior to insertion into the canon. For example, the portions of 1 Corinthians 14:33-36 that deal with women in church are thought to not be the words of Paul, but of someone who modified a copy of the letter at some later date (perhaps the same author who wrote 1 Timothy).
So, if your question was, "who wrote the earliest Christian texts?" the answer is very complicated. If you meant, "Who was the earliest historian?" then Origen, Clement of Alexandria, and Eusebius (AD circa 260-339) are the winners. 10 books, or chapters, of Eusebius' writings have survived and are compiled in,
The History of the Church, which I am in the process of reading.
Most texts that were deemed heretical were burned under orders from the Church. Much of what is known about earlier texts is from descriptions in the writings of Origen, Clement, and Eusebius. They provided detailed quotes of many texts that were deemed unsuitable for the orthodoxy of Christianity and mere mentions of others. Many no longer exist (i.e., The Gospel according to the Twelve Apostles and the Gospel of Basilides)
Other texts do exist, but not as originals. As with the texts that are part of the Christian bible, the earliest available documents are copies of copies of copies. The Gospel of Peter, the Apocalypse of Peter (hair raising, to say the least), and several apocryphal texts dating to the 8th century (originally written in the later half of the second century) were found in the tomb of a Christian monk in upper Egypt in 1886. Prior to it's discovery, it was known only as referenced by the early historians.
A large cache of early documents, including the Gospel of Thomas, and other texts that were considered 'gnostic' in nature (and ordered destroyed by the Church) were discovered in Nag Hammadi in 1945. Documents that became known as the Dead Sea Scrolls were found in 1947 in a cave 13 miles east of Jerusalem. These scrolls do not mention Jesus, John the Baptist, or any of the disciples. They are not Christian texts, per se, but provide a firsthand glimpse of life in the region at the time of the birth of Christianity.
There is plenty of fascinating material to read on early Christianity, both historical and contemporary in nature. Good luck on your search.