It was the first man and woman who brought sin into the world, Adam and Eve. The result of this original sin is that man is no longer immortal in the flesh but only the soul of man is immortal. It is because of this first sin that we may also sin for because of the sin of our original ancestor God’s plan has been circumvented and we no longer have the power over sin within ourselves. Because of this loss we are subject to the temptations of the flesh and have lost the intellectual ability to know God’s will or to receive His grace unless drawn to it by His Spirit.
Scripture is very plain as to the great loss this was to humanity and to God’s design for His creation:
(Psa 51:5 DRB) (51:7) For behold I was conceived in iniquities; and in sins did my mother conceive me.
(Wis 2:23 DRB) For God created man incorruptible, and to the image of his own likeness he made him.
(Wis 2:24 DRB) But by the envy of the devil, death came into the world:
(Rom 5:12 DRB) Wherefore as by one man sin entered into this world and by sin death: and so death passed upon all men, in whom all have sinned.
(1Co 15:21 DRB) For by a man came death: and by a man the resurrection of the dead.
(1Co 15:22 DRB) And as in Adam all die, so also in Christ all shall be made alive.
We also see from St. Paul’s writing that it is through the transgression of Adam that brings us “death through sin”. God also spoke through Isaiah:
(Isa 43:27 DRB) Thy first father sinned, and thy teachers have transgressed against me.
It is through the Gospel of Jesus Christ that we are saved through the Sacrament of Baptism from original sin.
(Act 2:37 DRB) Now when they had heard these things, they had compunction in their heart and said to Peter and to the rest of the apostles: What shall we do, men and brethren?
(Act 2:38 DRB) But Peter said to them: Do penance: and be baptized every one of you in the name of Jesus Christ, for the remission of your sins. And you shall receive the gift of the Holy Ghost.
(Act 2:39 DRB) For the promise is to you and to your children and to all that are far off, whomsoever the Lord our God shall call.
(Act 2:40 DRB) And with very many other words did he testify and exhort them, saying: Save yourselves from this perverse generation.
(Act 2:41 DRB) They therefore that received his word were baptized: and there were added in that day about three thousand souls.
(1Pe 3:21 DRB) Whereunto baptism, being of the like form, now saveth you also: not the putting away of the filth of the flesh, but, the examination of a good conscience towards God by the resurrection of Jesus Christ.