I'd like to see some evidence that Augustine changed the idea of original sin.
Here are some quotes from the Early Fathers from
Catholic Answers about original sin.
Hermas
“‘They had need,’ [the Shepherd] said, ‘to come up through the water, so that they might be made alive; for they could not otherwise enter into the kingdom of God, except by putting away the mortality of their former life. These also, then, who had fallen asleep, received the seal of the Son of God, and entered into the kingdom of God. For,’ he said, ‘before a man bears the name of the Son of God, he is dead. But when he receives the seal, he puts mortality aside and receives life. The seal, therefore, is the water [of baptism]. They go down into the water [spiritually] dead, and come out of it alive’” (
The Shepherd 9:16:2).
Theophilus of Antioch
“For the first man, disobedience resulted in his expulsion from paradise. It was not as if there were any evil in the tree of knowledge; but from disobedience man drew labor, pain, grief, and, in the end, he fell prostrate in death” (
Ad Autolycus 2:25 [A.D. 181]).’
Irenaeus
“But this man . . . is Adam, if the truth be told, the first-formed man. . . . We, however, are all from him; and as we are from him, we have inherited his title [of sin]” (
Against Heresies 3:23:2 [inter A.D. 180-190]).’
“Indeed, through the first Adam we offended God by not observing his command. Through the second Adam, however, we are reconciled, and are made obedient even unto death [Rom. 8:36, 2 Cor. 5:18-19]. For we were debtors to none other except to him, whose commandment we transgressed at the beginning” (ibid., 5:16:3.)
Tertullian
“On account of his [Adam’s] transgression man was given over to death; and the whole human race, which was infected by his seed, was made the transmitter of condemnation” (
The Testimony of the Soul 3:2 [inter A.D. 197-200]).
“‘Because by a man came death, by a man also comes resurrection’ [Romans 5:17]. Here by the word ‘man,’ who consists of a body, as we have often shown already, I understand that it is a fact that Christ had a body. And if we are all made to live in Christ as we were made to die in Adam, then, as in the flesh we were made to die in Adam, so also in the flesh are we made to live in Christ” (
Against Marcion 5:9:5 [inter A.D. 207-212]).
Origen
“The Church received from the apostles the tradition of giving baptism even to infants [Matt. 19:14; Luke 18:15-16; Acts 2:38-39]. For the apostles, to whom were committed the secrets of divine mysteries, knew that there is in everyone the innate stain of sin, which must be washed away through water and the Spirit” [Titus 3:5] (
Commentaries on Romans 5:9 [A.D. 244]).
“Everyone in the world falls prostrate under sin. And it is the Lord who sets up those who are cast down and who sustains all who are falling. In Adam all die, and thus the world falls prostrate and requires to be set up again, so that in Christ all may be made to live” (
Homilies on Jeremiah 8:1 [post A.D. 244]).
Athanasius
“Adam, the first man, altered his course, and through sin death came into the world. . . . When Adam transgressed, sin reached out to all men” [Romans 5:12]. (
Discourses Against the Arians 1:51 [inter A.D. 358-362]).
Cyril of Jerusalem
“Indeed, one man’s sin, that of Adam, had the power to bring death to the world. If by the transgression of one man, death reigned over the world, why should not life more fittingly reign by the righteousness of one man [Jesus]? If they were cast out of paradise because of the tree and the eating thereof, shall not the believers now enter more easily into paradise because of the tree of Jesus [the Cross]? If that man first formed out of the earth ushered in universal death, shall not he that formed him out of the earth bring in eternal life, since he himself is life?” [John 10:10, 14:6] (
Catechetical Lectures 13:1 [A.D. 350])
Also there is an article about Augustine and original sin:
Subtitled - "St. Augustine and original sin are not the boogeymen many modern Eastern (and Western!) scholars make them out to be"
It goes into the Eastern fathers as well as Augustine and concludes:
"Augustine read carefully and even made verbal use of the teachings of St. Gregory Nazianzus regarding original sin, and Gregory is “the theologian” of the East
par excellence. It never occurred to Augustine or to anyone else that his teaching was out of line with the teaching of the Eastern doctors. Indeed, Pelagius was condemned in the East, and Augustine listed among the approved teachers of the Church in ecumenical councils. There is no “original” Latin error in Augustine. He is a universal doctor just as are Chrysostom, Basil, and Gregory."