This is from Bart Ehrman's (subscription) blog, which I highly recommend. I'm not sure if I'm alowed to share it, but I don't think he'd mind. It talks about the earliest diversity:
The key point is that the differences affect not just the resurrection appearances. That’s just the tip of the iceberg. Destro and Pesce have maps of Palestine for each of the Gospels where they shade in where Jesus does or says anything. And the four different maps are very different indeed. In the three maps that provide shading for what you find in Mark, in the “special sources of Matthew” (that is, the material that Matthew has acquired from sources other than Mark or Q), and in the “special sources of Luke” – the only place of any overlap is Jerusalem. Mark has activities of Jesus up in Tyre, Sidon, Caesarea Philippi – basically places north and northwest of the Sea of Galilee. Luke’s special material does not have these places, but instead has places on the southern coast of the Mediterranean heading east to Jerusalem; Matthew’s special source has some overlap with Mark, but mainly it’s all up in Galilee north, east, and NE of the sea of Galilee. John on the other hand has almost none of that, but instead has a areas in Samaria and Judea. And so on.
Destro and Pesce use these data to make a very interesting argument. They think that Jesus, during his public life, was active in a number of areas of Galilee and Samaria and the Transjordan. In various places he would have acquired followers, who could not physically follow him around since, well, they did have to work for a living in order to eat. After his death, these groups of followers would have continued to adhere to his teachings – as they understood them. They would have told stories about him. Their views would have developed. And there is absolutely no reason to think that these various groups would have thought the same things about Jesus, remembered the same things about him, recalled the same teachings from him, or interpreted these teachings in the same way.
In other words, immediately as soon as “Christianity” (however we define that) began after Jesus’ death, there would have been small groups of Jesus’ followers in different places with different views. And these different interest groups’ stories are the ones that eventually were brought together in the various Gospels.
Destro and Pesce do not tie this into Bauer’s thesis about orthodoxy and heresy, but the connections are hard to miss. Diversity in the early Christian movement did not start with the Gnostics and Marcion in the middle of the second century. It was there from the beginning, as different followers of Jesus in different places had different understandings of what he said, what he did, and what he meant. These groups would have heard at different times that Jesus was raised from the dead. They would not have been connected with each other, unified with each other, seeing one another as all members of the same church. They were simply the followers of Jesus who may have known that there were other followers elsewhere (or not). We shouldn’t think of Christianity as starting out as ONE group of Jesus’ followers, who all swore allegiance to the disciples who set up the church in Jerusalem. It would have been scattered, disunified groups throughout Palestine. From the very beginning.