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Writer's pictureSophie Lozowska
10 min read

Love from the first scent? (scientifically based dating tips)

Have you ever had that amazing feeling of butterflies in your stomach, a sense of being in a muddle - those vague, exhilarating senses when you see THAT person? Let me help with the puzzle. The culprit is called the limbic system, a primitive section of the brain responsible for regulating essential functions like hunger..and apparently love.  


When encountering a potential mate, a part of the brain called the hypothalamus spurs the release of neurotransmitters such as dopamine and serotonin, causing the sensations of lust or love. The initial surge of attraction to someone involves a complex interplay between the sympathetic and parasympathetic nervous systems. The sympathetic system, responsible for the "fight or flight" response, can suppress desire if adrenaline activity is too low, which is why scientists suggest watching a horror movie on a date rather than a rom-com. As intimacy deepens, our "love" becomes associated with dopamine-mediated pathways, facilitated by the parasympathetic system that governs relaxation and pleasure. 


How attractiveness comes to play then? 

Behaviours are often genetic and may be inherited, reflecting traits that were evolutionarily advantageous to our ancestors. This perspective proposes examining the brain's development through the lens of evolutionary adaptation. Those who adapt best to their environment are more likely to survive, reproduce, and pass on their genes to the next generation. Within this tradition, humans are said to select mates that will enhance their reproductive success, and there has been a concurrent emphasis on the importance of certain species-typical features, some promoted by pop culture articles are: symmetrical facial features, physical fitness or youthfulness whether manifesting itself through clear skin or acts of altruism.  


But we are here to talk about pheromones, so first, let’s state some truths like the fact that in the animal kingdom pheromones’ role does not only come down to mate attraction. Pheromones are chemicals produced and released mostly by apocrine glands into the environment, affecting the behaviour or physiology of other or its species. Their primary function is to communicate in a general sense - to induce aggression or alarm, to advertise territorial boundaries, or to promote parent-offspring bonding. Kairomones for instance, are semiochemicals emitted by an organism that mediate interspecific interactions to the benefit of another species, often at the expense of the emitter. Ants release kairomones to help their colony members find their way home, but these chemicals also leave a trail that predators, like snakes, can follow. Another example is the bee orchid, which mimics the appearance and scent of a female bee. When a male bee is attracted and investigates, it becomes trapped and subsequently flies away with the orchid's pollen, facilitating the plant's reproduction.


Does it mean I will attract my date by walking outside soaked in Amazon pheromones?

The easy answer for impatient ones - we are extremely likely to release and be guided by pheromones because we are humans descended from animals yet no one has ever chemically identified a human pheromone. 


However, if you are here to find some actual scientific tips on dating we will start with a really simple study that talks a little bit about how important diet is in attracting a partner. In 2006 Havlicek and Lenochova investigated what would happen when male participants alternated between a red meat-rich diet and a largely non-meat diet. What was found was that female participants consistently judged the men's body odour to be significantly more pleasant when the men followed the non-meat diet, which included increased intakes of eggs, cheese, soy, fruit, and vegetables. This illustrates that consuming a healthier, plant-based diet can positively influence body odour and, consequently, attraction.  


History of bombykol - so how animals attract even without eating veggies. 

In 1959, Nobel-winning German chemist Adolf Butenandt and his team chemically identified the first official pheromone, bombykol, found in silkworm moths and used in sex attraction. Butenandt was a professor both in Germany and Poland and had been previously known for the chemical identification of sex hormones oestrone (1929), androsterone (1931), and progesterone (1934) and for this work, he shared the 1939 Nobel prize in chemistry with Leopold Ruzicka. 


A silkworm moth | Image credit: Chemistry World


What they found was that when female moths are ready to mate and flutter their wings, they release bombykol into the air currents. Males use their antennae to sense this pheromone as it travels through the wind. Once the scent is picked up, a male moth flies in a zigzag path, moving towards the increasing concentration of bombykol. The males’ antennae are covered with 17,000 hairs (sensilla), each containing thousands of pores. Approximately half of these hairs are specialised in detecting bombykol, giving each month over 20 million pores through which the pheromone can diffuse; you see, they sacrifice a lot to find a mate!


After the bombykol molecule enters one of the pores, it must navigate through a watery solution called sensilla lymph that surrounds the pheromone receptor cells. Since bombykol is hydrophobic due to its long carbon chain, it requires assistance to reach the receptor site. This help comes from a pheromone binding protein (PBP) that has charged groups on its exterior to attract water molecules, making it water-soluble. As the bombykol-carrying protein approaches the nerve cell membrane containing the receptor, it interacts with charged sites around the receptor, potentially involving a pH change in the aqueous medium. This interaction causes the carrier protein to alter its shape, disrupting the weak hydrogen and ionic bonds holding the bombykol molecule, allowing the pheromone to quickly bind to the receptor. This binding produces an electrical change in the receptor, triggering a nerve impulse sent to the brain.


Structure of B. mori pheromone binding protein (PBP), showing bombykol in the pocket of the protein | Image credit: RSC Education


But how did they do it?

During the time of the “bombykol project,” silkworms were used as the source of silk for the large European silk industry, which provided Butenandt with a ready source of thousands of silkworms for the initial investigation. Then it was time to extract bombykol, however, we first need to acknowledge that bombykol is produced in an abdominal gland, so its extraction is highly challenging. But, it is not the only molecule released, so secondly after identification, they had to separate it from other organic materials working with suuuuper tiny quantities (micrograms per millilitre) and with none of the sophisticated techniques available to the modern chemist, such as spectroscopy. Next, they performed bioassays, so in other words observation of moths in the presence of pheromone that led them to notice the previously mentioned “flutter dance”. Based on this knowledge, they created an experiment in which male moths were exposed to extract solutions of differing concentrations to find out the least concentrated solution required to produce the response. Then they purified the solution by fractionating and separating mixtures of liquids, gases, and solids into their components. The smallest concentration that would lead to the “flutter dance” in 50% of a sample of male moths was 10-12 micrograms of bombykol per millilitre of solvent. 


Molecule of Bombykol - C16H30O | Image credit: Alamy


As it all sounds neat, you would probably not assume that the purification took 20 years, whereas the identification of Bombykol took only one year! After World War II, the European silk industry collapsed, and Butenandt’s supply dried up. So, they ordered half a million female moths from Japan, which, after two years of painstaking extractions and separations, yielded 6.4 mg of pure Bombykol. After the introduction of spectroscopy, discovering the presence of an alcohol group and two double bonds (four possible isomers) went smoothly. Lastly, they confirmed Bombykol by synthesising it themselves, preparing all four isomers. One of these isomers was at least a thousand million times more biologically active than the rest.


Therefore, what is the debate all about?

The debate over the existence and functionality of human pheromones is both fascinating and contentious. Proponents argue that, like other mammals, humans secrete scents that can influence behaviour. Evidence supporting this includes a study by Doucet, which found that babies have a specific behavioural response to a particular smell, irrespective of whether it comes from their mother or any other lactating woman. This suggests a biological basis for scent communication. Furthermore, the fact that humans, like other mammals, secrete various scents throughout their lives—consider the distinct odour of a teenager's room, for example—bolsters the argument that we might possess functional pheromones.


On the other side, sceptics argue that generalisations from animal research do not necessarily apply to humans. Human mating behaviour is influenced significantly by cognitive and sociocultural factors, such as learned experiences and social norms, which complicate the simplistic view of pheromone-driven attraction. Critics also point out that studies on human pheromones often suffer from replication issues and small sample sizes. Additionally, while smells play a role in human interaction, they are not necessarily pheromones, as the human process of scent detection is highly complex and difficult to study. Moreover, despite some promising data, researchers have struggled to isolate specific pheromone molecules, relying instead on indirect evidence like graphs.


Olfactory pathways | Image credit: Catalyst University


A key aspect of this debate involves the vomeronasal organ (VNO), also known as Jacobson's organ. This organ is well-documented in animals for detecting pheromones and sending signals to the amygdala, which processes emotions, and then to the hypothalamus, which controls hormonal responses. However, its presence and functionality in humans are hotly debated. Some believe the VNO disappears during foetal development or, if it remains, lacks the sensory neurons necessary to send signals to the brain. This would render it nonfunctional. On the other hand, supporters of the pheromone theory argue that if the VNO is present, it could still play a role in a subtle form of communication-related to attraction, akin to its function in other animals. Therefore, in the debate, there are several factors, so even if we found the chemical structure of a human pheromone, the mystery of human scent and the impact of pheromones on our behaviour would not be fully solved.


Two studies to make you believe in pheromones:

The idea of reproductive fitness is central to understanding human attraction, as demonstrated by Claus Wedekind's famous 1994 T-shirt smelling experiment. People often detect each other's natural body odours subconsciously, much like how we perceive voices without realising it. Females, in particular, are “attracted” to the major histocompatibility complex (MHC) molecules, which play a key role in immunity and fertility. These molecules, composed of a large number of genes on chromosome six, help ensure healthy offspring. In Wedekind's study, 49 female and 44 male students from the University of Bern participated. Male participants wore plain, cotton T-shirts for two days without using deodorant or fragrance, and they avoided sex, alcohol, and smoking during this period. Female participants then rated the scents of six T-shirts: three worn by males with similar MHC genes and three worn by males with different MHC genes. 


The results showed that women found the odour of men with different MHC genes more pleasant. Interestingly, women taking oral contraceptives preferred the scents of men with similar MHC genes. This study highlights the influence of MHC on attraction, supported by the compound androstadienone, found in male sweat, which has been shown to improve mood, emotional focus, and sexual arousal in heterosexual women as well as highlighted the importance of menstruation circle in mating behaviour. 


Another experiment, conducted in Sweden, revealed even more intriguing results, suggesting that sexuality is closely connected to attraction to pheromones. Swedish researchers used brain imaging techniques to show that homosexual and heterosexual men respond differently to two odours that may be involved in sexual arousal, with gay men responding similarly to women. The oestrogen-like compound activated the usual smell-related regions in women, but in men, it lit up the hypothalamus, which governs sexual behaviour. Conversely, the male sweat chemical primarily activated the hypothalamus in women and the smell-related regions in men. These two chemicals seemed to have a dual role, functioning as an odour for one sex and as a pheromone for the other. When the experiment was repeated with gay men, their response to the two chemicals matched that of the women, leading to the conclusion that the hypothalamus's response is determined not by biological sex but by the individual's sexual orientation.


Here comes the conclusion…

The topic of pheromones is quite ambiguous and I apologise for not helping out with your love life directly. We can say there are some limitations in the presented studies and theories. Everyone lives in their chemical world, influenced by the context of memories and the connection between senses. Different olfactory systems mean that there is no fixed set of chemicals in our noses. Nerves from the brain are exposed in the olfactory bulb, with over 400 receptors on their ends that work in a combinational fashion. These receptors come in different variants, so everyone has a unique olfactory system that affects how we perceive and respond to scents.


A big issue is also that we learn what smells good and what to avoid, with cultural influence being so strong that it can suppress a child's natural urge to smell everything because it’s "new." For instance, we are taught to appreciate the aroma of blue cheese as a "national specialty" despite its strong odour. Additionally, much of what we do as humans involves connecting senses to experiences, which shapes how we perceive certain smells. Scents must be rooted in our memories, as they travel from the olfactory bulb to the limbic system, then to the hippocampus and amygdala.


Our dating style has changed from secreting clouds of pheromones around ourselves, as insects do to mate, to swiping on tinder. So if you picked up this article to find some dating tips, here they come: eat your veggies, do not buy pheromones on Amazon, sweat a lot, do not be afraid of dating people of other races - you may end up with healthy offsprings - and.. be a scientist!


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