Saint Augustine (354-430) was the first theologian to teach that man is born into this world in a state of sin. The basis of his belief is from the Bible (Genesis 3:17-19) where Adam is described as having disobeyed G-d by eating the forbidden fruit of the tree of knowledge in the Garden of Eden. This, the first sin of man, became known as original sin.
Many Christians today, particularly members of the Anglican, Roman Catholic, Lutheran, Methodist, and Presbyterian Churches, subscribe to this belief. They maintain that the sin of Adam was transferred to all future generations, tainting even the unborn. Substantiation for this view is found in the New Testament (Romans 5:12) where Paul says, "Wherefore as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned. By one man's disobediance many were made sinners."
Christianity believes that only through the acceptance of Jesus that the "grace" of G-d can return to man. A Christian need only believe in Jesus to be saved; nothing else is required of her.
The doctrine of original sin is totally unacceptable to Jews (as it is to Christian sects such as Baptists and Assemblies of G-d). Jews believe that man enters the world free of sin, with a soul that is pure and innocent and untainted. While there were some Jewish teachers in Talmudic times who believed that death was a punishment brought upon mankind on account of Adam's sin, the dominant view by far was that man sins because he is not a perfect being, and not, as Christianity teaches, because he is inherently sinful.
Sources: Kolatch, Alfred J. The Jewish Book of Why/The Second Jewish Book of Why. NY: Jonathan David Publishers, 1989.