That comes later when someone decides to sin, before that there can be no real evil, only potential evil, which doesn't make you evil any more than being able to commit a murder makes you a murderer. People become corrupt and can become less corrupt upon their choice, they are born good though.
As a Christian, I believe that though God originally created man "very good," though with the freedom to choose evil, man corrupted himself by sinning against God so his nature is presently depraved in every part. This does not mean that every man is as bad as he could be (we see many people, unbelievers included, who are at least outwardly upstanding people), but it does mean that in every part of man there remains corruption. I do not see how there can be any other explanation for man's evil in the world. If he were naturally good (or a blank slate, as ladiesman suggests), that could not answer how man can be so exceedingly wicked at times, as we see in various genocidal regimes.
On the question of whether or not human nature is innately good or innately bad, Rousseau would say that man is innately good, our very essence is to be virtuous. In contrast, Hobbes and Machiavelli says man is by nature wicked, selfish and competitive. I think humans are neither naturally virtuous nor naturally vicious, human nature has both good and evil tendencies.
I mean..Human's definitely possess the ability to be kind, but it just turns out that humanity has bad qualities. Who knows what we'll do in the future but if you look at humanity's track record, we're not exactly "peaceful" or "free of sin". Instead of getting along,we kill each other,rape each other,harm each other, and insult each other.
Why? I don't even know. We have done SOME good,but our evil's definitely out shadow them.
Rather than the silly idea of "original sin", perhaps it is partly because going way back into the dim dark ages we were told to think we were something special. We regard ourselves as different from, and better than all other life. We practice violence, tyranny, indifference and thoughtlessness towards all other species, and then are surprised that is how we learn to treat each other. Either we need to wake up soon, or, when we successfully wipe ourselves out, if we don't take them with us, the rest of the animal kingdom and the planet itself will be breathing a huge sigh of relief.