Leo XII never made a solemn declaration that Eve literally came from the side of Adam. In discussing the origins of marriage, he notes this fact from Genesis, taking it for granted. There’s no question of a solemn definition.
That having been said, Catholics currently are obliged to believe that Eve was created from Adam’s side. This is according to a declaration of the Pontifical Biblical Commission made back in 1909, and that hsn’t been revoked.
Still, there is no question of a solemn definition. So, although we are required to give assent to this teaching, I suppose a Catholic scholar or scientist would be within his rights to treat an opposing belief on a merely hypothetical level.
Or perhaps not. The reason why the Church insists that all men, even Eve, came from Adam, is that this has profound implications for the doctrine of Original Sin. Original Sin was not contracted when Eve ate the fruit; it was contracted when Adam did. Just as we Christians have a supernatural solidarity with the one man, Christ, and so can be saved; so, on the natural level, we all have a sort of solidarity with the one man, Adam, in whome we have lost sanctifying grace.
If Eve was not in some way biologically “descended” from Adam, then it would seem that she was exempt from Original Sin (though not from personal sin).
Then again, a theologian might someday find a way of reconciling this, if in fact her generation from Adam is not to be literally understood.
Mary was born from the side of the new Adam ( the spear wound in the side of Jesus).
I think you’re getting your analogies mixed up.
The Fathers do use this analogy, but only when they speak of
the Church, not Mary, as the New Eve.
Yes, Mary is also in a sense the New Eve (and the Fathers acknowledge this). But in this case it’s got nothing to do with the spear wound in Christ’s side.
In fact, if I’m not mistaken, the Fathers comment at the paradox: while the first Eve was generated from Adam, the Second Adam (Christ) was actually generated from the Second Eve (Mary). **