Most people agree that the original sin was when Eve at the forbidden fruit. But Dr. Sedler, in his book "When to Speak Up and When to Shut Up," sets forth the theory that Adam was present when Eve decided to sin and he did not speak up to advise her against it. He says that this is the original sin--the fact that Adam said nothing when his companion was making an unwise choice.
It is our responsibility as Christians to speak up when our friends and family members are making wrong choices. We must, however, do it with an attitude of love and humility.