From Luke Timothy Johnson’s “Among the Gentiles”:

When the evidence in Acts is considered together with that in the earliest epistolary literature, a number of historically responsible statements can be made about the earliest stage of the Christ cult within the Greco-Roman world. First, the movement spread with impressive speed: within 10 years of the death of Jesus, there were communities of believers in Judaea, Samaria, and Syria (Acts 1-11); in 15 years, communities could be found in Asia Minor (Acts 14); in 20 years, through Asia Minor and into Greece (Acts 16-18); and in 25 years, in the capital city of Rome (Acts 28:14)-with ambitions to spread the movement also to Spain.16 Such rapidity of expansion is the more impressive when it is remembered that the evidence for the movement’s spread concerns the existence of ekklesiai (associations, gatherings, communities) and not simply the conversion of individuals.

The rapid pace of expansion was not entirely due to enthusiastic reception of the message wherever it was brought. The earliest missionaries experienced harassment and persecution (primarily from fellow Jews and incidentally from Roman authorities), so that movement from one place to another was impelled as much by rejection as by acceptance.IS Christianity’s itinerant expansion began not after a long period of settled existence in Jerusalem but immediately and under less than ideal circumstances. Within two decades, the nascent movement was forced to negotiate geographical, cultural, linguistic, and demographic transitions. 19 The transitions had to be accomplished, moreover, under conditions not only of external duress but also of internal instability. The most prominent leaders of the cult were killed within the first 30 years.20 The “mother church” of Jerusalem was impoverished and in need of assistance from other communities.21 Even when it tried, it could not offer effective control over a movement that had spread over such a vast area at such a rapid pace.22 Nor could coherence be accomplished through textual controls-there was as yet no collection of Christian writings, and Torah scrolls were not easily transported or deployed in circumstances of rapid expansion.23

All these factors help explain the diversity of expression and perspective in the earliest Christian writings. Christianity was, in the first generation, virtually something new everywhere it appeared, taking its shape from the experience and conviction of the local or itinerant founder, the conditions and response of those who joined the movement, and the combination of social circumstance and continuing experience of communities through time.