“Every storyteller wants it to be true,” says Tristram Wyatt from the University of Oxford. “But analysed in more detail, it probably isn’t happening.” A plethora of studies have failed to replicate McClintock’s original findings, and after poring over the data, one of her post-doctoral researchers found that it might be a statistical artifact. In other words, this phenomenon is just as likely to occur by chance as through chemical communication. The frequency, length (five days out of 28), and variability of menstruation in women make synchronisation very likely.

Back in the 70s, however, the apparent discovery was the source of much excitement. Off the back of McClintock’s study, the British physician Alex Comfort published a commentary titled the Likelihood of Human Pheromones, stating that it would not be long until the first human pheromone was discovered.

He was right.

That same year, H A Cook, writing in New Scientist, purported to have found at least two examples in human breath and sweat. One, as far as he could judge, had the same odour of garlic. “This occurs in human female breath when the female is sexually aroused, and is not caused by the eating of garlic,” he wrote at the time. Cook went on to suggest that this pheromone aroused males, and was the reason women use small amounts of garlic in cooking. “The second human pheromone is the smell of fear, which is certainly apparent to dogs,” he continued, not taking into account the species-specificity of pheromones.

Such claims were easily discounted and ignored. But others stuck. Follow the trail of supposed sex pheromones in humans and you arrive at a conference held in Paris in 1991.