What do the bicycle and the internet have in common? One less than obvious answer is that they have both encouraged sex between strangers. The introduction of new technologies can often result in dramatic, and largely unforeseen, effects on societies, disrupting established patterns of doing things and connecting people in unexpected ways. In his book The Discovery of France, the historian Graham Robb describes how the sale of 4m bicycles before the first world war had a striking impact on French society. One consequence was probably to make the French taller. As Robb writes: “A boy with a bicycle could leave his pays in search of a job or bride and be back in time for dinner, which is why the bicycle has been credited with increasing the average height of the French population by reducing the number of marriages between blood relations.” The French love of the bicycle, it seems, encouraged passion of a different kind. The internet may be having a similar effect as it broadens the social connections that people make. Steve Jobs once even described computers as bicycles for our minds, although their ability to facilitate amorous liaisons, like the pre-first world war velocipedes, was probably not what he had in mind. The sociologist Mark Granovetter theorised about the strength of weak ties. According to this idea, you are more likely to find a job through a loose acquaintance than a close friend because they can access a broader network of contacts. That is the appeal of LinkedIn. But an academic paper published this month explores the potency of what it calls “absent ties” in the marriage market thanks to the rise of online dating sites. Whereas many of us still marry people we meet through friends of friends, colleagues or neighbours, more and more of us are now hitching up with complete strangers we first discover on the internet. The likes of Match.com, OKCupid and Tinder are the algorithmic matchmakers of our day. In the US, one-third of marriages results from online dating. Tinder, which launched in 2012, has about 50m users and produces 12m matches a day. One of the paper’s authors, Josué Ortega, who studies game theory, became intrigued by these dating sites while teaching at Columbia University and wondered how far they were responsible for breaking down racial segregation. Although many of his students were using Tinder for casual sex, he was also struck by how sometimes it led to more permanent relationships for older users, such as a professorial colleague in his 70s who met his second wife via the app. “New technology gives us more options,” says Mr Ortega. “And these options have unexpected effects on society.” To explore how such networks might work in theory, Mr Ortega and his co-author Philipp Hergovich built a mathematical model of online connections. They came to two stark conclusions: these networks should result in markedly higher rates of inter-racial marriage and a lower rate of divorce (because of the greater compatibility of matches). How do these findings match the observable data? Overall, according to the Pew Research Center, only 6.3 per cent of marriages in the US are inter-racial compared with 9 per cent in the UK (although it should be remembered that such marriages were illegal in parts of the US until 1967). But the number of inter-racial marriages has shot up in the US since the introduction of online dating sites. The authors also cite separate research showing that marriages initiated online result in fewer divorces. Absent ties may indeed make the heart grow fonder. Of course, correlation is not causation. The relatively recent introduction of online dating sites (Match.com launched in 1995) means that the data are of short duration. And mathematical models have a hard time accounting for messy human emotions such as blind love. Whatever the cause, the authors argue that the rise of inter-racial marriage is a good thing because it helps promote social integration. But those with a particularly strong sense of ethnic identity might not see it that way. It may increasingly be the case that our societies will divide between some groups defined by ethnic identity and others bonded by social values. We obsess about white supremacists marching through Charlottesville while largely overlooking how seemingly trivial technologies, like Tinder, are reshaping our societies in more subtle and important ways.