Odor Compatibility: The Reason Our Scents Attract Partners And Friendships

It doesn't take much to realize whether someone smells good to us or bad to us. Sometimes we meet someone who, at least on a surface level, smells so great that we want to be near them all the time. On the other hand, we sometimes meet someone who doesn't smell right to us. Like, something is definitely off and we'd prefer to stay away from that person. We don't know why, we can't explain it, but we just know that they're not our people. And it's true — they're not. 

Whether we're cognizant of it or not, how we smell and how others smell to us is why we have the friends we have and why we choose the partners we choose. We just automatically feel a connection with those whose natural smell — sans deodorant, perfume, and other scents — makes us feel comforted and, in the case of partners, even aroused.

If you find yourself not offended by the body odor of those around you that can come after a long, sweaty summer's day, or if you even love that smell, there are reasons for it.

When it comes to friendships, it's about compatibility, having things in common, and sharing similar, if not the same values. But while all these things (and more!), make for great long-lasting friendships, smell actually plays a role before we even know these details about a person.

According to a June 2022 study published in Advance Science, when people felt an instant connection with someone else, as opposed to a friendship that evolved over time, the friends smelled very similarly. Even when the researchers brought in a group of strangers, collected their smells from t-shirts that were worn the night before, then asked the group to stand in pairs and mimic each other's movements, the results were the same: those who felt an immediate click with someone had a similar scent than those where there was no instant connection because their body odors were so different.

In 1995, Swiss zoologist Claus Wedekind conducted what we would be known as the "t-shirt experiment." Similar to future studies that used t-shirts to obtain body odor, Wedekind took 49 women and 44 men, asking the latter to wear t-shirts for two nights. When the t-shirts were returned, the researchers put them in boxes with holes so the women could smell the shirts, rating them from pleasantness to sexiness. As the study found, most women were attracted to the smells of men who were genetically different from them, therefore, making them a romantic match or "the one," so to speak. 

It's here that Charles Darwin's theory of survival of the fittest comes into play. While Darwin didn't rely on t-shirts to prove his theory, he surmised that through natural selection, people — or any organism for that matter — would inherently choose those with different genetic makeup, securing that any children that are had will have the best chance at surviving.

Which brings us to...

When scientists talk about genes in regard to mate selection, they're talking about the major histocompatibility complex (MHC) genes or, as it's referred to in humans, the human leukocyte antigen (HLA), which are components of the immune system. As Darwin predicted and as Wedekind found with this famous "t-shirt experiment," when looking for a partner, we naturally gravitate toward those who have opposite genes from us. The reason why is purely linked to evolution and procreation, and because of this, according to a 2016 study by Scientific Reports published in the National Library of Medicine, sexual and partner satisfaction are at their highest when we're with someone whose immune system genes are unlike ours. 

When two people come together with varied immune systems, their offspring are going to have a strong immune system that will, ideally, be able to fight off disease and infection, giving the child a better chance at a healthy long life so, they too, can find a mate with different immune system genes than their own and procreate. Because of this, each generation gets stronger and stronger, and more able to fight off disease. Even if you have no intention of having children, you'll still be attracted to those who have opposite immune system makeup than what you have, and that attraction will stem from how your partner smells to you and vice versa. 

Although ancient monarchies would marry their cousins so as to keep the bloodline, well, royal, what they didn't know is that ultimately that was a bad idea. Inbreeding, which involves procreating with someone who has the same MHC and HLA as you, results in creating a genetic combination that isn't just potentially harmful to the offspring, giving them less of a chance at survival, but can even cause some major genetic defects. It doesn't matter which animal you pluck off the planet, inbreeding isn't doing the species any favors.

It's because of this that we're actually able to sniff out those who are related to us, even if it's subconscious, and steer clear of them when it comes to romantic and sexual attraction. Which also means that those cultures, in which marrying within the family is seen as an essential part of keeping their bloodline pure, probably aren't particularly attracted to their partners. They may think they are for the sake of the bloodline, but because evolution trumps what we force ourselves to believe, the reality is that these couples probably aren't as into each as they would be if their genes were opposite.

While the various studies that were conducted only focused on same-sex friends and heterosexual couples, because of the impact body smells has on same-sex friends, one can't totally rule out that this likely says something about same-sex romantic relationships. Takeaway? Maybe ditch the perfume for a change and see who you attract. You might be really surprised.