Do Single People Smell Different?

 You would be forgiven for thinking that the best way to smell attractive is to cover up your natural scent, based on the size of the market for high-end fragrances. But what if our own smell was the key to impressing a date? 

Our genetics play an important role in determining the smell of our BO, meaning that everyone's smell is unique to them. We know this because wins BO is so similar that test participants are able to match two t-shirts worn by twins when mixed up with other random t-shirts. In fact, participants in this experiment couldn't tell the difference between twins t-shirts and two t-shirts worn by the same person. Our noses are surprisingly perceptive to human smell, and contained in that smell is all sorts of information about a person's diet, fertility, age, health and genetics. So can we use that information to make choices about who we date? Well, heterosexual men find women's BO more pleasant during the follicular phase of their menstrual cycle, when women are at their most fertile, and least pleasant during menstruation, when women are at their least fertile. This may have been evolutionarily important because if a woman is more attractive to a man at a time when she is actually fertile then it's a good investment of resources for the men to approach her at exactly this time. 

This led scientists to ponder; can we smell attractive people? To answer that, Ilona Croy and other researchers like her use smelly t-shirts worn by strangers to test participants' noses. In one study, participants were given a range of t-shirts and asked to rate them based on their BO. Women found that single men's t-shirts smelled stronger than married men's t-shirts which might be useful information if you're looking for a date. Similar scent-based attraction studies have found a curious link between BO preference and something called HLA dissimilarity. HLA is a group of proteins that play a role in coding for some of our immune response. Everyone's HLA profile is slightly different, and reveals which kinds of diseases we have immunity to. It is also heritable, so we pass on some of that immunity to our children. From an evolutionary point of view, it is an advantage to have offspring with someone who is HLA dissimilar, meaning their immune system defends them against a different set of diseases. This means that their offspring is very likely to be heterozygous, meaning that offspring has a high variability against a large variety of pathogens. And this means that that it's very beneficial if I mate with someone who has a different immune system than I have. 

In some studies, single people have been found to prefer the BO of HLA dissimilar individuals. These studies suggest that we might be able to use our sense of smell to pick out good mates. However, the most comprehensive study of its kind found no link between BO preference, HLA dissimilarity and chosen partners in 3,700 married couples. Basically, while we are able to tell the difference between good BO and bad BO, we probably won't end up choosing who we marry based on their smell.