What does love smell like?
If you’re a polar bear, it turns out love smells like feet. Polar bears leave footprints in the snow impregnated with their scent and these little frozen clues left across miles of ice are enough for polar bears to find each other. This could be crucial for polar bears who are usually solitary creatures, only mating at certain times of the year.
If you’re a wasp (Dasyscolia ciliate), then love smells uncannily like the Ophrys speculum orchid, aka the mirror bee orchid. In addition to looking like the bee, this clever flower uses additional sexual deception to emit the odour of the female wasp, thereby attracting the male wasp to engage in mating behaviour during which pollen is transferred ready to take to other orchids. The result of more orchids instead of wasps in this highly specialised behaviour is vital to the orchid’s survival – the wasp is the exclusive pollinator.
1-octen-3-ol is an insect attractant, used in lures, being attractive to many insects including mosquitoes, sand flies, midges and tsetse flies. 1-octen-3-ol is an important classic fungal mushroom odour. It’s present in many natural things, including immature truffles and mushrooms. Crucially it is produced by many mammals during oxidative breakdown of linoleic acid (an essential fatty acid) in the skin. If you’re a blood sucking insect, 1-octen-3-ol smells lovely, it smells like lunch.
You may know that the smell of truffles are desirable to female pigs because they contain an odourant pheromone, androstenone, which is found in the saliva of the male pig. Sows seek the truffles but are so excited they often eat them. Dogs have largely taken over as truffle seekers because they can be trained to recognise and find truffles, and most importantly, not to eat them. Androstenone is also found in human sweat, but it does not illicit the same behaviour as in the pig (thankfully) and studies show wide variations in detection and descriptions of androstenone in humans.
For a baby rabbit, it could be argued that love smells like rabbit milk. A baby rabbit will respond with immediate feeding behaviour in the presence of rabbit milk and a series of experiments determined that the feeding response was induced by the milk odour, which contained over 150 different odourants. Amazingly, just one, 2-methylbut-2-enal was found to be the behavioural cue, the rabbit pheromone.
Benoist Schaal’s research highlights that the odour of human breast milk attracts babies to feed, and even non-breastfed babies are attracted to the smell of human breast milk over and above the smell of formula milk. It’s unknown if just one or several odourants contained in breast milk could be responsible for this innate desirability. Human babies feed in a relaxed ongoing way, so are not ideal subjects to repeat test preference for dozens of odouants in order to find out which one is the trigger, so maybe we’ll never know.
In humans, genes in the major histocompatibility complex (MHC) influence how we smell and how we look, both of which influence our preferences for potential mates. Several studies have demonstrated that women prefer the odour of men with dissimilar MHC types but similar looks, suggesting a sweet spot target for dissimilarity. Related studies also show pregnant women prefer MHC similar smells, suggesting a greater affinity for family when pregnant - perhaps due to the protective environment family is expected to provide. There is also evidence that our perfume selection is influenced by our MHC type, perhaps that we are drawn to scents which echo or magnify our essence.
Love has a smell for humans too, more appreciated now due to Covid related sensory loss. Your partner's unique scent is a key factor signifying familiarity, security, harmony and passion, can reduce stress and promote restful sleep. The sense of smell has a very important for its role in intimacy, family relationships, social support and emotional wellbeing. With each breath we can be reassured (or not) that we belong. Covid patients suffering from long term changes in their ability to smell and taste describe feeling disconnected from themselves and others. They cannot smell their partners and children or worse, parosmia (which can give awful smell distortions) can result in aversion. Long term absence of the smells of loved ones can cause measurable distress and depression.
Our breaths take in all kinds of sensory information including temperature, moisture, smell and a bit of love.
Love smells different depending on who and what you are, it’s not always kind or true or even consistent. Yet, the common thread joining these love scents is survival. What does love smell like? Perhaps at its basic level love smells like survival.
What does love smell like for you?
References for further reading:
Orchid seduction: https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:648125-1
Polar bear paws http://onlinelibrary.wiley.com/doi/10.1111/jzo.12181/abstract and https://www.cbsnews.com/news/polar-bears-find-mates-with-scratch-and-sniff-footprints/
Insects and Octenol http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3481478/
Androstenone and humans http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1664751/
Rabbit pheromone http://www.nature.com/nature/journal/v424/n6944/full/nature01739.html
Babies attracted to mothers milk smell https://www.sciencenews.org/article/newborns-nurse-long-term-memories-smells and https://www.newscientist.com/article/mg21128333-500-bumpy-nipple-smells-guide-babies-to-milk/
MHC types and humans http://www.researchgate.net/profile/S_Roberts/publication/23569567_MHC-correlated_mate_choice_in_humans_a_review/
MHC and perfume preferences https://academic.oup.com/beheco/article/14/5/668/186534
Covid related smell problems https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8462678/#idm139662310909680title