I asked a friend who is a jenu-wine NT scholar about a comment of Tony Campolo's comment about the church being pacifist in its first three centuries. He asked in return "If someone asked you what the church believes in the 20th C, what would you say?" And after a pause, he smiled ans said "It was about the same then." I was reminded of this in the context of our NT study, which is describing the beliefs of Palestinian Jews in the 1st C. Christians tend to say things like "Well, the Jews in Jesus day believed..." However you fill in that blank, you're in trouble.
We extend that type of mythical thinking to the early church, because it makes it easier to talk about and remember. But it isn't so. The church was unified from about the time of Thomas's acknowledgment of the risen Christ until a bit after Pentecost. About Acts 5, actually. Or maybe only sundown on Pentecost. Not even halfway through that book there is a description of a dispute about Gentiles and the Law, and with some effort, they came back into accord.
The picture may come from the early Protestants, who in their contention with the Roman Catholic Church, painted that varied communion as more unified than it ever was. Or perhaps it was the Catholics of that time in their contention with the Protestants, extending the idea of universality, wholeness, and agreed core doctrines into a less-accurate monolithic picture of themselves. (This wasn't the only juncture where such ideas might firm up, but it's the one we are most familiar with.)