Unreached people groups were made for oral Bible storytelling! Most historians and theologians believe that long before Moses wrote the book of Genesis, the stories were passed along in oral form. From Creation to Moses, they believe the stories were orally passed from one person to another.
When Moses preserved these stories in written form, he emphasized the value of hearing the stories of God: “These commandments that I give you today are to be upon your hearts. Impress them on your children. Talk about them when you sit at home and when you walk along the road, when you lie down and when you get up” (Deut 6:6).
When Jesus spoke to the crowds, He did not tell them anything without using stories. (Matt 13:34). Jesus used stories because most of his audience was oral learners.
Peter and John were probably oral learners: “When they saw the courage of Peter and John and realized that they were unschooled (“agrammatoi” in Greek, meaning “illiterate”) and ordinary men, they were astonished and took note that these men had been with Jesus.” (Acts 4:13).
And so it was that “the word of God spread and the number of disciples in Jerusalem increased rapidly.” (Acts 6:7). Many Church historians believe that in the 40 years after Pentecost (before the New Testament was written) a church was started in almost every major city of the Roman Empire!