© 2015 Gayil Nalls
Source: © 2015 Gayil Nalls

Under our brash and busy world is a subtler world, a world that has always been there for humans.  It is an invisible bridge between self and others that is part of the sensory life of each of us. It is a type of communication and learning capacity that is fundamental to our social bonding and the interconnectedness we need for survival.

Despite our differences, or maybe because of them, the human olfactory system, with its connections to our brain’s limbic structures and memory processing, is able to characterize the molecular biochemical signals of other humans. We have always had the remarkable ability to correspond, perceive and experience others through our sense of smell. Human beings have evolved to bond deeply, and to pre-reflectively be guided by this powerful and vital biological information we each emit.

The link between sensory input and behavior is firmly established, as is the link between olfaction and memory. However, social odors and how they create a level of understanding and the mechanism of their mental processing has only recently become a highly active area of scientific research. We now know that through smell we gain insights into a range of information, including the biochemical aspects of the immune systems of others. We may sense disease processes such as diabetes, lung disease, cancers, and the metabolism of schizophrenia.

Our sensitivity to airborne molecules, odorants transferred to us, is paramount as we navigate our daily lives, moving from bed and our co-sleeping partners to crowded subways and packed escalators and elevators. Through our sense of smell we create spatial understanding of our surroundings and gauge our encounters with strangers. We recognize potential threats of dominance or anger, and bask in molecules of empathy. At times we smell another’s fear, a contagion that travels through a crowd, and make it our own.

Our perspiration is our unique chemical identity that communicates everything about us from our gender and state of mind to the foods we eat and drugs we take. As hormones have specific smells, recent studies of the smell of sweat found that blindfolded volunteers were able to distinguish sweat-soaked armpit pads of the elderly from other age groups.  This is yet another step in our firm understanding of how social odors influence and orchestrate a variety of human behaviors in our encounters.

The fact that humans emit molecules that attract or repulse was evident in another study in which the musky smell of middle-aged men, who make high levels of aggressive hormones, was found to be the most intense and unpleasant among the samples representing different age groups and genders. Also, through the olfactory sense we recognize the odorous particles of a potential mate. Again, with T-shirt testing, researchers have determined that men can smell the concentrations of certain compounds that occur when a women is most fertile.

In a larger picture of the human life cycle, we have come to understand that human DNA changes throughout the stages of life, and just as one’s age can now be identified from DNA testing, age can also be identified from one’s aromatic chemistry. Humans release chemicals that signal different stages in an individual’s life cycle, from the much-loved smell of infants before their bacteria biome has developed and their immune system has matured, to adolescents, when hormones and pheromones become active, to dying and the ester gasses of death.

All through life each of us is a walking odor plume that leaves a scent trail wherever we go, and surprisingly, it is a marked path that can be detected and followed by other humans. Despite our reduced number of odor detecting receptor cells when compared to animals such as dogs, researchers have verified that humans can detect and follow a scent trail too.

As we move through the crowded streets of the world metropolises, we continually encounter the subtle world—social odors, capable of activating and conditioning hormone-driven behavior. With the global population growing, it may be time to consider that the dynamics of our collective primal human olfactory systems, though invisible, may be the most important structure of our cities.

© 2015 Gayil Nalls, All rights reseved.

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