Original sin is not a Biblical teaching.
The creation of the pagan doctrine of original sin can be traced back to 4th Century Rome, where the pagan philosophies of Gnostics and Manicheans blended into Christian teaching. Unfortunately, this erroneous doctrine has had an inordinate influence on evangelical dogma and how the Gospel is preached.
Augustine of Hippo is the first to formulate the flawed doctrine. As a student, he studied under the Manicheans, who had a dualistic worldview which saw the material world as inherently evil; therefore seeing all humans as evil by nature from the day of their conception.
Augustine's background in pagan philosophy set the stage for what would be his idea of grace, faith, and salvation. This flawed idea is of severe negative consequence because it is through his efforts that the doctrine of original sin pollutes much of Christian teaching to this day.
Before Augustine, no one taught that humans were born sinners and therefore that there freewill is in bondage to their flesh.
In fact, the Old Testament contradicts Original Sin. One example is Ezekiel 28:15 which says, "You were perfect in your ways from the day you were created ..."
Another example is Ecclesiates 7:29 which says, "Truly, this only I have found; that God made man upright, but they have sought out many schemes."
The false doctrine of Original Sin plainly contradicts the Bible and erroneously makes God the author of sin.
The teachings of the early Church Fathers, who were direct descendants of Jesus' apostles, also contradicts Original Sin. The early church talked about sin as an action or an illness, Augustine and others shifted language to an inborn sin nature.
Justin Martyr (c. 160) said, "Unless the human race have the power of avoiding evil and choosing good by free choice, they are not accountable for their actions, of whatever kind they be."
Tatian (c. 160) stated that, " ... nothing evil has been created by God; we ourselves have manifested wickedness; but we, who have manifested it, are able to reject it."
The doctrine of original sin renders the Gospel ineffective. It destroys man's free will and turns God into a tyrant by God demand something man is incapable of doing.
Read more here about how Original Sin Is Biblically Refuted