"Fun inside a girl has some pretty drastic biological consequences if not very careful. And who, back then, was careful?"
All who were monogamous. Or virgins. That´s one part of the value of virginity.
"The other "serious" biological concern usually takes 9 months to resolve."
But that´s not The End. Children and grandchildren ought to be forever, not for 9 months only.
"(Females don't have penises. Fingers do not inject DNA ladened semen.)"
They can break virginity, though. Visigothic law mentions offence of breaching virginity with a hand.
"The idea of rape was originally due to the "property" concept a man had over a female (of any age.) Virgins, back then, were worth more than a thousand goats and horses. Take that "value" away from one of his females, and the "owner" is going to get really pissed off."
If the thousand goats and horses belong to the virgin herself, she is still really pissed off to have them robbed or stolen.
A reasoning why a father, or mother, is pissed off to have their daughter defiled... is that he has been made a single grandfather.
The father´s aim was to get a rich and loving son-in-law, a knight in shining armour wrapped around his daughter´s little finger, able and willing to support all the children she will bear. He wanted someone else (the son-in-law) to pay for his grandchildren.
And now his daughter is defiled forever, a red-headed stepchild he has to pay for (because its father won´t) is the only grandchild he will have, because no knight wants his daughter any more.
Now consider the case of a son making a teacher pregnant.
The logical question for the concerned grandparent would be:
"Are you on the hook for the mother and child?"
If the answer is "Yes", the grandparent is basically as badly wronged. The boy gets stuck with a red-headed stepchild instead of a better bride and better children he might have got.
But if the answer is "No", the father can congratulate the boy. The grandchild in question is still someone´s red-headed stepchild, supported by teacher´s birth family or unwitting husband - but the boy is still free to get the better bride and the better children in future. The red-headed stepchild comes on top of, not in stead of, a family of better children, and is therefore a modest win, not a great loss as in case of the child stuck with parental responsibility.