By some interpretations, sentience is the original sin (or at least the consequence of it.) Adam and Eve ate from the tree of knowledge, after all, and if you take the serpent at its word, the knowledge was to "be like God, knowing both good and evil."

Then again, the original sin is more likely to be disobeying God to begin with. Although that leads to a chicken and egg question of how it was possible for Adam and Eve to be talked into disobeying God to begin with if humans didn't have the capacity to sin at the time.