Ok, the exact reason that Christians say that every person is a sinner out of the chute, (Except one, but he wasn't completely human since he was part godstuff) is because of that evil woman Eve. Even though she was tempted by the Satan-snake beyond her ability to resist. Additionally, after she became a sinner, she tempted Adam (by some accounts with her feminine wiles) and he too became a sinner.
Because of that, the landlord kicked them out of the garden, forced Adam to take up rake and hoe when before all things were given them. And he caused Eve to suffer greatly during childbirth. (I kind of wonder about that was since Eve didn't give birth until *after* they left Eden, so how could she know it was greater suffering?)
He also damned the snake and Satan too. At least he was consistent.
And the landlord said that all their descendants would be damned as well because of their transgression. I think that was kind of immature for a being that is supposed to be infinite and ageless.
It wasn't until he sent his son (which was himself) to earth to suffer and die did that sin get forgiven. But only to the select few who accept the landlords son as their Saviour and are baptized in his name. That is why children who are baptized are considered to be without sin as all is forgiven at that point.
Depending on which branch of Christianity you accept, those who came after Adam and Eve but before the landlords son are damned and are in hell. Also those who have not heard of Christianity or reject it are also damned. This from the guy that knows all and sees all.
-Sandy