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Agreed, we are discussing issues prior to original sin. I am using Last Common Ancestor in the sense used by geneticists in developing trees of life. That perspective sees no discontinuity at any point in evolution, and most certainly does not entertain our specific religious problem of ensoulment, a necessary and irreducible discontinuity from our perspective. 

In imagining, in speculating, about a solution, I accept direct creation by Yahweh in the sense of ensoulment as inescapable, but see no reason to imagine the direct creation of the bodies of our earliest ancestors (which you seem to see as required?). Indeed, Yahweh directly creates everyone of us in the womb by a similar act of direct creation, of ensoulment of sexually reproduced biological matter. I suggest that once one ponders the equivalence of that first ensoulment and all subsequent ensoulments, each an instance of direct creation, then the starting point disappears as a problem.
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