The women of the 19th-century urban poor were at it. Sneaking around, getting some. That, anyway, is the conclusion drawn from some recently reported DNA research, published in the journal Current Biology.

The authors of the paper compared the Y chromosomes of 513 pairs of men who supposedly share a common ancestor to determine the prevalence of what they called “extra-pair paternity” over the past 500 years – in other words, the number of times in the men’s family trees that the father named on the birth certificate wasn’t the same as the man who supplied the sperm.

For most of the period, the rate was stable at one in 100. But the researchers’ analysis identified a spike in the 19th century, when the level went up to six in 100. What caused this? The Industrial Revolution.

While procreation stayed closely tied to marriage bonds in the countryside, the rapidly increasing urban population lived in an intimacy with each other that made sex outside marriage more possible that ever before. This was reported as “an uptick in adultery”, although the researchers acknowledged that sexual violence played a part too: not every extra-pair paternity event was consensual.

There’s an inevitable glint of salaciousness in the way this has been reported. And the idea of the Victorian woman loosening her stays for a passing fancy fellow, then presenting the resulting baby to her clueless husband as his own, has a certain piquancy to the kind of man who hangs around on internet forums inveighing against the general untrustworthiness of females.

As presented, extra-pair paternity sounds like a kind of con that modern science can at last unravel, the cuckoos in the nest finally revealed and the unhappy chaps who raised another man’s child made subject to retrospective sympathy.

But such a view forgets that life for women in the urban working classes was precarious at best (something that the historian Hallie Rubenhold has written about movingly in her book The Five, a group biography of the victims of Jack the Ripper). The available jobs were poorly paid and unreliable. To be a woman alone was to skirt along the bleakest fringes of existence; to be a woman alone with a baby was to have almost no prospects at all. The imperative was to find a man who could provide some legal standing, some financial security and some social shelter in an inhospitable world.

Did all the men raising children who weren’t genetically their own know? Of course not. But many would have done and though the researchers may be correct that extra-pair paternity is little studied from a genetic standpoint, the private mythologies of families abound with these stories, few of which sit safely within the prudish label of “infidelity”.

The parlour maid whose master ruined her, but set her up with a dowry with which she could be safely married off to a male servant. The deserted woman who supported herself and her children with a makeshift procession of temporary husbands of no lawful status.

And, yes, the one who was having a good time and got away with it. Marriage is a patriarchal invention and nothing the patriarchy made was ever done in women’s interests: marriage exists precisely because men sought to control the female body and not all female bodies have submitted easily to that control.

The untidy true story of paternity is really the story of how insufficient our institutions can be when they try to contain the messy truth of human feelings. Desire will defy lawful bonds, brute survival will best romance, and love – those fathers who cared for their sons, regardless of “extra-paternity events” – will refuse the mean calculus of genetics.