==Introduction==
Tracing the origin of the canonical Gospels has proven exceedingly difficult. While Christians generally believe the Gospels were written by Matthew, Mark, Luke and John in the mid-first century AD, modern scholarship has failed to verify those claims. All four Gospels, therefore, are nowadays considered anonymous. Dating them has yielded no better results; they can be dated plausibly anywhere between c. 30 and 150 AD (or c. 30-180 AD for John), with a more probable range of c. 60-130 AD (or c. 60-150 AD for John). Further narrowing relies almost exclusively on speculation.

The Four Canonical Gospels

The Gospel of Matthew — traditionally the Apostle Matthew, son of Alphaeus; actually anonymous

The Gospel of Mark — traditionally Mark, who wrote down the narrative given by the Apostle Simon, called Peter; actually anonymous

The Gospel of Luke — traditionally Luke, who wrote down the narrative given by the Apostle Paul, who was formerly called Saul; actually anonymous

The Gospel of John — traditionally the Apostle John, son of Zebedee; actually anonymous

The Earliest Possible Dates

To get an idea of the low end cutoff, we must acknowledge that since Jesus was crucified under Pilate, the Gospels could not possibly have been written before 26 AD, when Pilate took office. However, such an early date for the Gospels, while arguably plausible, is extremely unlikely. The accepted authentic Pauline Epistles (those being. Romans, 1 &. 2 Corinthians, Galatians, Philippians, 1 Thessalonians, Philemon and possibly Colossians), which are dated to c. 50-60 AD, make no mention of the Gospels. It is, therefore, very likely that the Gospels were written down some time after this time period. The probable low-end cutoff, therefore, is c. 60 AD.

Internal evidence, namely the reference to the temple's destruction, suggests the Gospels were either written or edited after 70 AD. However, it is possible that the references are only coincidental, and that they were included prior to 70 AD.

The Latest Possible Dates

No clear references to the Synoptics occur until c. 130 AD, by Papias, which seems strange given the references to the Pauline Epistles by 1 Clement (c. 95 AD), and Ignatius (c. 110 AD). However, the subject matter of 1 Clement and the unusual circumstances under which Ignatius wrote may explain their mutual silence. Unfortunately, even Papias' testimony is somewhat suspect, as it survives only in a fourth-century quotation. Because of this, the 130 date is not absolute, but only probable. It does not apply at all to John.

In c. 150 AD, Justin of Rome quotes all three Synoptics, calling them the "memoirs of the Apostles." This reference is actually a retelling of a debate supposedly held in c. 135 AD. This suggests that the Synoptics had been written no later than c. 135 AD, and authorship ascribed no later than c. 150 AD. Justin also makes a possible allusion to the Gospel of John, but it is too ambiguous to use as an absolute cutoff. The Apostles, however, would have been long dead by this time, so Justin is unhelpful in confirming tradition of authorship. He is extremely important, though, because he provides an absolute cutoff of c. 150 AD for the Synoptics. Irenaeus provides the first clear reference to John in c. 180 AD, which is therefore the latest possible date for that particular Gospel.

Authorship

Let's take a moment to address the age of the Apostles at this point, which is helpful for assessing the likelihood of their involvement in the Gospels' compositions. Since Jesus died during Pilate's term in office, that means it must have occurred between 26 and 36 AD. Supposing, then, that the Apostles were adults, and that they were no more than five years older than Jesus (who was probably 33 or so when crucified), this puts their own births between 12 BC and 20 AD. In 60 AD, therefore, the Apostles' ages would probably be between 40 and 72. By 90 AD, they would have been between 70 and 102--though even the oldest is not likely to have made it past 90 or so.

The Didache quotes the Gospel of Matthew, but calls it the "Gospel of Our Lord." Several problems with this reference render it essentially worthless in establishing the date of the Synoptics, but it is a fascinating point of evidence otherwise, because it suggests Matthean authorship was attributed later--and thus erroneously.

Unfortunately, the various claims of Apostolic involvement are unlikely at best, and absurd at worst. The Didache, along with the age restrictions of the Apostles, suggests Synoptic authorship was incorrectly assigned after they had been written. No convincing evidence exists to support the traditional Apostolic authorship, leaving all four Gospels anonymous.

External Links

Most of the above information was drawn from the following source:

The Canon of the New Testament - Bruce Metzger

...which is summarized in this free online article:

The Formation of the New Testament Canon - Richard Carrier