We are now approaching a social revolution in which the economic foundations of monogamy as they have existed hitherto will disappear just as surely as those of its complement-prostitution. Monogamy arose from the concentration of considerable wealth in the hands of a single individual – a man – and from the need to bequeath this wealth to the children of that man and of no other. For this purpose, the monogamy of the woman was required, not that of the man, so this monogamy of the woman did not in any way interfere with open or concealed polygamy on the part of the man. But by transforming by far the greater portion, at any rate, of permanent, heritable wealth – the means of production – into social property, the coming social revolution will reduce to a minimum all this anxiety about bequeathing and inheriting. Having arisen from economic causes, will monogamy then disappear when these causes disappear?
One might answer, not without reason: far from disappearing, it will, on the contrary, be realized completely. For with the transformation of the means of production into social property there will disappear also wage-labor, the proletariat, and therefore the necessity for a certain – statistically calculable – number of women to surrender themselves for money. Prostitution disappears; monogamy, instead of collapsing, at last becomes a reality – also for men.
In any case, therefore, the position of men will be very much altered. But the position of women, of all women, also undergoes significant change. With the transfer of the means of production into common ownership, the single family ceases to be the economic unit of society. Private housekeeping is transformed into a social industry. The care and education of the children becomes a public affair; society looks after all children alike, whether they are legitimate or not. This removes all the anxiety about the “consequences,” which today is the most essential social – moral as well as economic – factor that prevents a girl from giving herself completely to the man she loves. Will not that suffice to bring about the gradual growth of unconstrained sexual intercourse and with it a more tolerant public opinion in regard to a maiden’s honor and a woman’s shame? And, finally, have we not seen that in the modern world monogamy and prostitution are indeed contradictions, but inseparable contradictions, poles of the same state of society? Can prostitution disappear without dragging monogamy with it into the abyss?
Engels, Friedrich. Origin of the Family, Private Property, and the State; Chapter II.4.https://www.marxists.org/archive/marx/works/1884/origin-family/ch02d.htm