Original sin is not part of the original teachings. (We are not born sinners as we incarnate again and again from lifetime to lifetime to work out our karma and grow spiritually)
Original sin is a religious 'control' device, as is the hierarchy of the early church -- that the word of God came first through the bishops and priests, who were God's representatives, and then to be passed out to the laity as they saw fit.
So, original sin, Jesus, the redeemer of sins, who died for our sins, and several other foundational beliefs of modern Christianity were add-ons.