original sin: a both/and?

in some follow-up thoughts to my last post, i've been thinking that maybe this extrinsic v.s. intrinsic debate on original sin is really a both/and.

if my premises are right that our ethics come from culture which comes from human relationship (with God, humans and creation), and our ethics are screwed up because our relationships are screwed up, then what happens when we consider that to be a human being-- ontologically-- is to be cultural and relational? in other words, human beings have a relational/cultural dimension, and when we are born into a relational/cultural tainted world, then the moment that dimension begins taking shape that part of us is tainted.

now i understand that this won't satisfy those who insist that a human being, in utero, is already depraved. but if we understand that being human is more than just biology, then i think my explanation that sin comes from the outside, but immediately affects our relational/cultural dimension from the very beginning of our life could be a satisfying explanation.