How is it that someone who lived thousands of years ago can "represent" me? The assertion that all of humanity "sinned" when Adam sinned, or "through Adam" is often made as a foundation to other Christian doctrines. What specific doctrine points to Adam being a representative of all of humanity? According to those who hold this doctrine, by what mechanism can Adam be considered my representative? I never voted for him nor was offered a choice to participate in his blood line. How is it logical that the choices he made should be held against me and the rest of humanity?

Furthermore, are my other blood ancestors such as my father and grandfather also my representatives in the same sense? If not how is their role different?

The tag original-sin has some interesting related questions, but nothing dealing just with the mechanism by which Adam is considered a "representative", a common phrase used by Christians.
I didn't get to vote or have any say in my forebears leaving their homelands and emigrating to the United States (or, The New World, as it was then known in Europe); nor did I have any say in whether or not to participate in their bloodline. Yet they represented me when they did it.

If we take the Bible to be God's word, and we believe that God cannot lie, then we also have to believe that Adam and Eve were the first people on earth, and that they had the choice to not sin - but of their own free will chose to disobey God.

It is not "Christianity" which says we are sinners because of Adam's sin, it is the Bible that says such:


  Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned


&amp; here:


  For since by a man came death, by a man also came the resurrection of the dead.


&amp; here:


  all have sinned and fall short of the glory of God