Ayn Rand’s Repudiation of Original Sin

In one of her letters, Ayn Rand confesses that if she "were to select only one idea as the most depraved ever conceived by man," the doctrine of original sin "is the one I would pick." How did Rand understand this long-standing religious notion, and why did she have such a negative evaluation of it? What does she think are the implications that embracing original sin has for one's moral life? Where did she see expressions of the idea in her time and how do they still shape our culture and politics today?