It seems to me that the way our mainstream biblical scholars still see the early history of Christian gospels can be best compared with Creationism. After all, each of our mainstream Synoptic theories today -- whether it is 2ST (Two Source Theory), 2GT (Two Gospels Theory), or Farrer -- is premised essentially on the assumption that all of the Synoptic gospels somehow emerged into the world in a single act of creation -- each put together by a single writer, it seems, an exegetical genius of some sort, locked up in a private study somewhere, and isolated from all the others. And after each of the gospels had been written down "during the first century", it had been frozen textually, more or less, somewhat miraculously perhaps?
But what I'm offering here, on the other hand, is essentially an evolutionary view of gospels' history. And, on this view, no single date of creation can ever be affixed to any of our 4 canonical gospels. Their development was a continuous process, that started perhaps even before 70 CE, and continued well past 200 CE. And, all throughout, while this process unfolded, there had been a lot of cross-pollination among the gospels -- the sort of a cross-pollination that's usually pretty obvious even to a casual reader. After all, especially after the 4 gospels had been assembled together into a single edition ca 170 CE, the whole collection was owned by the Church, so all 4 gospels had a potential common editor who was quite interested in making their accounts appear more harmonious.
And, in general, I find that if one discusses these matters with non-professionals, for a change, they will usually express no surprise at all upon hearing that the Church continued to develop and "improve" these works for quite a long period of time as it saw fit. After all, it's a common enough assumption that the Church was the owner of these texts right from the beginning, so why wouldn't their owner continue to make some "improvements" to them, if it saw the need to do so?
