Is the doctrine of Original Sin biblical? 

We search in the Bible to understand the root causes of evil and the original sin and how it is applied to people today. We look at age of accountability and see how it is in the bible. we search through and reference through the psalms and David's lineage and past to understand where God stands on these doctrines. At the end of this we come to a conclusion. Is it based in the bible to be accurate...?