Boots is going to do an over-the-counter paternity test that should, if nothing else, put Jeremy Kyle out of business. It's no cheaper than the ones sold online, but that's not the point. Previously, DNA tests were for men crazed with jealousy, or looking for ammunition on the brink of a break-up. High-street availability marks a leap from "doable but extreme" to "acceptable, bordering on respectable". I personally ceased to associate Boots with respectability when they moved their tax affairs to Zug, but you know what I mean: it's a little bit like if they decided to sell poppers.

The figure that Boots quotes for "uncertain paternity" is one in 25 children. I imagine this came from Sperm Wars, the popular science moment of 1996, in which Robin Baker cited a study that said 4% of human conceptions involve sperm from multiple men. The real notorieties of this book are its views on rape (actively sought by the woman as a way of testing the fighting spirit of the man) and on homosexuality (doesn't really exist). But at the point it came out, the uncertain paternity was the headline argument.

I remember my dad saying that this was a rather conservative interpretation, since those were just the conceptions that occurred with multiple sperm in play at the same time, and didn't count those in which the sperm of the husband was interspersed with other sperm over a period of weeks. He thought the true figure was more like one in 10. It sounded to me like projection: he had a son, who he knew about but hadn't met, who thought his father was someone else altogether. My family is full of question marks like this. When people have children, and then they turn out to be other people's, there's always an attempt to stratify it: it's the underclass, or it's bohemians, or it's a DNA-test debacle on daytime telly. But it happens everywhere, and when people insist that it doesn't I increasingly think, chum, you just aren't concentrating.

But however widespread the question marks are, I am extremely sceptical about whether anyone will take up the opportunity to test. First, Boots might not necessarily normalise the process of paternity testing. It could go the other way, and dent its own vanilla image through its association with this product. At the moment the test, Assuredna, connotes the same peeping sleaziness as that dust you can buy to check if anyone's been shagging in your bed (since you ask, it is called SemenSPY).

Second, there is international precedent with over-the-counter DNA sampling. The US pharmacist Walgreen's launched a "discover your DNA" kit (the test wasn't for paternity, but for predisposition to disease) that was immediately withdrawn by the Food and Drug Administration (FDA), for reasons which have some crossover application here – considerations of consent, authenticity, storage and information-sharing. How can a child be considered to have given meaningful consent to a tissue sample? Does the sperm-donor anonymity argument work, that it's in the best interests of the child to know its real father?

Donna Dickenson, emeritus professor of medical ethics at the University of London, says that the medical benefit is hard to discern here. What are companies even going to do with the samples? Assuredna say they incinerate them, but there are no legal guarantees or requirements for paternity testing generally. (In the US case some companies kept them, and were suspected of trying to compile a DNA database that they could flog to advertisers or drug salesmen. You have to tip your hat to entrepreneurship like that.) Those tests, incidentally, were already available online and still are: it was only their availability in a mainstream outlet that troubled the FDA.

Third, it isn't lack of availability that's been standing, all this time, between a father and his copper-bottomed DNA-ratified certainty. What prevents most fathers seeking a paternity test is a fundamental trust that exists between people who aren't compelled to be together for any reason beyond inclination. That isn't enough to guarantee that everybody's related to who they think they're related to, but it seems to be enough to preclude most people even wondering.

An interesting study came out last week in which the social psychologist Abraham Buunk examined "mate-guarding" in different societies – those in which parents arranged their child's marriage, compared to those in which the couple themselves made the choice. In cultures that kept the sexes separate, marriages tended to take place for social, political or financial reasons, centring on the wishes of the parents, not the couple. In cultures where a love-based choice was the norm, mate-guarding was rare. The author remarks: "In western cultures, most husbands do not actively try to prevent contacts between their wife and other men and may even accept a moderate degree of flirting." This is not a veiled attack on Islam: a large part of the study was based in Argentina, where different levels of parental involvement occur for a variety of non-religious reasons.

The study points to one huge boon of love-based culture: the act of choice has given us trust. It doesn't need to be serviced with DNA check-ups, it simply exists. And while some of us might be wrong in that trust, most of us are right.