So why did we pick February 14 as the day to celebrate love? And why is it called Valentine’s Day? As there are several stories going around, we don’t have the definitive answer for you. One of the most common explanations is that the name derives from the Christian priest St. Valentine of Rome. Legend has it that at the time, an imperial law was in place prohibiting soldiers to get married, because bachelors were believed to be more prepared to die in battle. But St. Valentine is said to have wed soldiers in secret, as he thought loved conquered all. When Emperor Claudius II found out about this, he had the priest executed on 14 February 269, making Valentine a martyr for love.

Cupid is not commemorated specifically, but was the Roman god of love or lust. According to ancient myth, whoever is struck by an arrow will fall in love with the first person they see. This is why Cupid symbolizes luck at first sight and often adorns Valentine’s Day cards. All-in all it would appear the Romans ignored the olfactory aspect of physical attraction.

Chemistry in love

Does ‘chemistry’ really make us fall in love or is that a thing from the movies? Which hormones contribute to physical attraction? Professor of Chemical Biology Luc Brunsveld opened his pharmacology textbook for the occasion. This gave Cursor something to work with, as it turns out fact-checking online information in this specialized area is pretty difficult for journalists without a chemistry or biology background.

Anyway, without further ado: yes, chemistry is involved in attraction. “It’s a combination of different types of molecules, such as dopamine, serotonin, noradrenalin, oxytocin, testosterone, and estradiol. The roles and ratios of the molecules varies according to the stages of love (initial/lust/bonding-oriented attraction/attachment),” Brunsveld teaches us.

Via the nose

With around 17 million people living in the Netherlands alone, we should probably be happy we’re not attracted to everyone. You wouldn’t get much else done. But what singles out those exceptions among the crowd that do give you that special feeling in the pit of your stomach? Smell turns out to be a major ingredient. A smell is the sensory stimulation of the olfactory membrane in the nose by a cluster of molecules. There are certain body odors that play a role in human sexual attraction, a subconscious process in which people use a potential partner’s body odor to determine whether they will pass on positive traits to the offspring. So body odor can provide us with important clues about the genetic quality, health, and reproductive success of that potential partner. Brunsveld: “But that doesn’t mean that if someone is too far away to smell them, there’s no attraction by default. There are simply too many aspects at play when it comes to physical attraction. And the ratios of the molecules involved also change as it passes through its different stages (initial/lust/bonding-oriented attraction/attachment). Testosterone and estradiol in particular are very powerful molecules that are not only key in the development of secondary sexual characteristics, such as breast tissue and a wider jawline, but also determine your sex drive. If you have more testosterone, you generally have a higher sex drive.”

There are a few different ways in which body odor influences sexual attraction, including via human biology and the menstruation cycle. The olfactory membrane plays a role in smelling and subconsciously judging other’s people’s pheromones. This is not unique to humans, as it also happens in the animal world.

For example, research has shown that for heterosexual women body odor is strongly linked to physical attraction. One study group of women even deemed body odor a more important aspect of attraction than looks.