Not something else.
It is like it is because God created everything in wisdom. God wisely used genes.
So concupiscence is transmitted to all through natural generation because it is transmitted by genes.
Its not fHansen’s question but interesting from a purely speculative point of view.
All the Church commits to is that the propogation is through the body not the soul.
How exactly through the body we do not really know.
The medievals thought it was through the male line only and that this conclusion was fully consistent with theological principles. That is why, I suppose, Aquinas famously erred (or rather didnt foresee) re the Immaculate Conception. In this medieval view there would be no need for Mary to be completely without sin to produce a child free of Original Sin. If there was no male seed involved in there would be no OS anyways.
It is very interesting that Aquinas and many of the Scholastics did not have their way on the issue of Mary’s Immaculate Conception in medieval times. Very interesting because it suggests a flaw in their, until then, seamless garment Scholastic approach to OS.
And the discoveries of modern embryology vindicate the Church in her affirmation of the ImmConc as “required” for a better understanding of the mechanism of OS and its propogation.
In the light of modern embryology and ther discoveries of egg and sperm made only 150 years ago we do see the conclusions of the medievals were based on flawed scientific premises.
For if we went along with them we would now have to say, in the light of modern science, that OS is passed down through the Y chromosome which is only from the male, and that the X chromosome is free from “defect”.
But then that means females must be free from OS which is obviously against Church teaching. So its a case of new embryology requiring new theological principles.
It seems the medievals were in fact mistaken to believe that OS is passed down through a defect in male “seed”.
And in fact the whole propogation by sex angle is now thrown into complete confusion. We have to accept this statement as a theological principle confirmed by the Church I suppose. But in the light of modern ebryology and genetics it seems to still lead to more of a dead end than it did in medieval times.
You suggest above that it is due to a defect in the genes (presumably of both male and female). Yet this is a very sterile approach to the issue that was not the case with ther medieval understanding.
At least in their understanding there was a spiritual aspect to this propogation. They considered semen to be very powerful at a spiritual level. It was not really a seed but a sort of architectural life force that formed protoplasm from the female - and its own matter did not enter into the formation of the embryo. So the defect was in the semen’s spiritual formative properties.
We see this spiritual life-force power at work in the speculations of the Eastern Fathers as to what sort of physical sex would have taken place before the Fall. They do not see the need, to be blunt, for penetrative sex. They seemed to suggest it would be enough for Adam and Eve to embrace with the intent of having children and the combined spiritual intent would have been enough to form a conceptus in the female. Thus the concept of virginal motherhood in Eden was asserted - due to the ancients largely believing carnal sex always involved some form of evil intrinsically. In other words carnal sex was necessitated by the Fall but that allegedly was not God’s original plan for us. (The same seems to go for bodily excrative functions which are considered “dirty”, the paradisial food was such that nothing was left unused when passing through the body. And again with childbirth, babies in Eden would not pass down the birth canal as that would destroy virginity. Hence the assertions of extra pain in childbirth outside Eden and why we have those traditions that Mary’s virginity remain intact even during childbirth - even to the extent that Jesus magically caesared through the abdominal wall as was the case with Buddhe 600 yrs prior).
But if we try and duplicate this sort of thinking into modern genetics it doesn’t work. Modern genetics is totally “materialistic” in understanding the process, no room for the communication of spiritual defects via a purely physical propogation mechanism that has completely lost its “spiritual” aspects.
And as we cannot say that God creates new souls with OS before they inform flesh…we are left without any decent solutions to this propogation of OS by sex teaching anymore.
It must be to do with something more than genetics.
It is something defective in materiality itself I suggest. Its not just human flesh that is wounded, the very soil itself is somehow implicated aslo.
Enough raving.