A small thanks to the resident Theists..

[Aractus]

Or that none of the gospels were written before 70AD. None of the original manuscripts survives, and the estimates of when they were written depend, not surprisingly, on whether or not you need for the dates to conform to pre/post-destruction of Jerusalem. The Christian must presume that they were written before, else they won't seem genuine. The non-Christian can approach the writings as they would any other ancient text purporting to describe specific future events in enough detail to make them clear.

Okay, a few things, let's work in reverse-order. "Any other ancient text", well let me repeat the example I've already given you.

Up until about 20 years ago it was general consensus among historians that the Egyptian Pyramids were built by slaves. This was based on one single source, written by a contemporary Greek historian in the 5th century BC. Herodotus visited Egypt c. 450BC, and was told that the pyramids were built by slaves.

Then, the graves of Egyptian workers were excavated alongside one of the pyramids, and now every historian believes that none of the pyramids were built by slaves - even though, and here's the interesting part, it's still equally possible that some pyramids were built by slaves and others by workers - after all they were built centuries apart!!

So don't presume to go on to me about what constitutes an acceptable level of evidence, if the single piece of writing by Herodotus is enough to convince historians that the pyramids were built by slaves for 2400 years, then I expect to see counter-evidence that is at least equal to the evidence that I've provided, not a simple dismissal of the evidence.

We don't need to presume when they were written, we do what is done with all historical documents, we date it as best we can from the available internal and external evidence. The fact that none of the Gospels mention the destruction of Jerusalem, makes it highly likely that they were written before that evident. The fact that Luke does not record Paul's death in Acts makes it highly likely that Paul has not yet died; Luke ends with Paul under house arrest, there's no other reason for this. Note that no events past AD 61 are recorded in the book of Acts; even though the book starts "historically" and ends in the "present". This is what gives us the most solid dating of the writing.

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None of the original manuscripts survives

This is true for most ancient texts, correct? Would you really expect papyrus originals to still exist vs parchment copies?