The father’s natural obligation to feed his children brought about the institution of marriage, which designates who must fulfill that obligation. The peoples  of whom Pomponius Mela speaks  determined it only by resemblance.
Among organized polities, the father is the man whom the laws, through the ceremony of marriage, have declared necessarily to be such,  because they find in him the person they are seeking.
This obligation, among animals, is such that the mother can usually suffice ; it is much more extensive in humans : their children have reason, but it comes to them only by stages ; it is not enough to feed them, they must also be guided ; they could already live, and they cannot govern themselves.
Illicit conjunctions contribute little to the propagation of the species. The father, who has the natural obligation to feed and raise the children, is not fixed in place at that point ; and the mother, who is left with the obligation, encounters a thousand obstacles from shame, remorse, the inhibition of her sex, the rigor of the laws ; most often she lacks means.
Women who have subjected themselves to public prostitution cannot have the convenience of raising their children. The strains of such education are even incompatible with their condition, and they are too corrupt to have the confidence of the law.
It follows from all this that public continence is naturally linked to the propagation of the species.