The concept of original sin was first alluded to in the 2nd century by Irenaeus, Bishop of Lyon in his controversy with certain dualist Gnostics. Other church fathers such as Augustine also developed the doctrine, seeing it as based on the New Testament teaching of Paul the Apostle (Romans 5: 12 -- 21 and 1 Corinthians 15: 22) and the Old Testament verse of Psalms 51: 5. Tertullian, Cyprian, Ambrose and Ambrosiaster considered that humanity shares in Adam's sin, transmitted by human generation. Augustine's formulation of original sin was popular among Protestant reformers, such as Martin Luther and John Calvin, who equated original sin with concupiscence (or "hurtful desire"), affirming that it persisted even after baptism and completely destroyed freedom. The Jansenist movement, which the Catholic Church declared to be heretical, also maintained that original sin destroyed freedom of will.

Answer this question based on the passage: when did the doctrine of original sin begin? Let's have some stream of consciousness first.
This is the relevant information: The concept of original sin was first alluded to in the 2nd century by Irenaeus, Bishop of Lyon in his controversy with certain dualist Gnostics. So, the answer is the 2nd century.