All human life does bad things, whether you want to call it sin or not.
http://en.wikipedia.org/wiki/Vanishing_twinhttp://www.ulm.edu/~palmer/Mother.htmStill, there are more disturbing things that happen in other parts of the animal kingdom. And doesn't it make sense to attribute more sin to the male gorilla who cannibalizes his newly won harem's children who were fathered by another male? Surely the gorilla has ethical responsibility. He experiences a "face to face" encounter ala Levinas (though I admit not being deeply read in Levinas). Yet we only ascribe "original sin" as a human phenomenon.
I think this means we should take a gradualist approach. But I'm still not sure.