"Why did Jesus choose the Apostles; why single out anyone at all if there is to be no hierarchy?"
The culture of that day for itinerant rabbis was for them to have students, disciples, who followed him around and learned on the job. When Pentecost came there were more than 120 male disciples and additional women followers. Out of the Jerusalem church after the persecution started the disciples scattered across Egypt, Africa Italy and Greece spreading the Gospel. These weren't Apostles, but disciples. Priscilla and Aquilla and Apollos were converts of these dispersed disciples and they did not look upon the church as hierarchical.
thanks for your reply; I'm sure others have and will discuss the structure of the Church post-Christ on earth.
What I'm still wondering, what an itinerant rabbi having "students, disciples, who followed him around and learned on the job" doesn't quite answer, is: Why did Jesus choose the 12?
thanks very much..