Biology 202
2002 Third Paper
On After taking a mixture of mind-altering drugs one night, Stephen D., a 22-year-old medical student, dreamed that he had become a dog and was surrounded by extraordinarily rich, meaningful smells. The dream seemed to continue after he woke up- his world was suddenly filled with pungent odors.
Walking into the hospital clinic that morning Stephen reports that he, "sniffed like a dog". And in that sniffing he recognized before seeing them, the twenty patients who were there. "Each had his own smell-face", he said, "far more vivid and evocative than any sight-face." Stephen also recognized local street and shops by their smell. Some smells gave him pleasure and others disgusted him, but all were so compelling that he could hardly think about anything else. (1).

Most creatures that wiggle, slither, swim, walk or just plain sit, survives by their noses. (4). The story mentioned above is just an example of the power that the olfactory system posses, or rather another example of the extraordinary brain at work as it is the brain that interprets the information received by the olfactory system and attempts to make sense of it. Stephen was able to distinguish one individual from the other nineteen people present at the clinic by simply using his sense of smell. My curiosity of the olfactory system lies within this primary question; can the nose's ability to distinguish between such scents as food and wet grass also be intricate enough to "sniff out" a potential mate?

Our culture places such low value on olfaction that we have never developed a proper vocabulary for it. In A Natural History of the Senses, poet Diane Ackerman notes that it is almost impossible to explain how something smells to someone who has not smelled it. There are names for all the pastels in hue, she writes - but none for the tones and tints of a smell. (1). Why would we choose to ignore the importance of one of our primitive senses? Some anosmics suffer from depression and their quality of life is severely affected primarily because many expectancies of life, such as memories, taste, and the possibility of finding a mate, have all been hindered by their inability to smell. (11). Yet, sometimes we fail to see the value of this sense, and its potential genetic worth; i.e. finding a mate.

(13).

In order to understand how this sense might, (I use the word might because scientists have not agreed that it is a fact), aid in heightening sexual desire and consequently our choice of lovers, we must first examine the olfactory system itself. We think that we smell with our noses, but this is a little like saying that we hear with our ear lobes. (7). That simple, short rush of air up the nose that we inhale when we breathe plays an integral role in our sense of smell. Specialized receptor cells of the olfactory epithelium detect and recognize smells. The air passes through the nasal cavity through a thick layer of mucous to the olfactory bulb. The smells are recognized here because each smell molecule fits into a nerve cell like a puzzle piece. The cells then send signals to the brain via the olfactory nerve. The brain then interprets those molecules as the sweet flowers, or the curdling milk that you've held up in your nose, or as some scientist want us to believe as the sweet aroma of love. In this sense each receptor is like a key on a typewriter, and each molecule types on several letters to produce a word, the odor. The "words" are then sent to the olfactory bulb, a pine nut-sized part of the brain right above the nose, where the words are turned into olfactory sentences. (4).

(11).

Humans can detect over ten thousand different smells. The sense of smell is a primal one. It is one of the most important means by which our environment communicates with us. (3). Smells are really airborne molecules that find their way onto our noses from the outside world. Inside the nose are the sensitive receptors that can detect a huge range of smells. The brain then works out whether you have encountered this smell before and if so, what it is. Pleasant? Repulsive? (5). In this respect, you can think of sensory systems as little scientists that generate hypotheses about the world. (6).

(13).

Each sensory system has a code for the information it receives. The olfactory system encodes odors by chemical composition. There are over one thousand different olfactory receptor proteins found on neurons in the nose, each of which recognizes a particular chemical feature of some odor molecules. The neurons send their signals to the brain's olfactory bulb, where each of the thousands of little clusters of neurons called glomeruli receives input from olfactory neurons with just one receptor type. That means each smell should activate a unique pattern of glomeruli - the "code" for that smell. (2). If humans can distinguish between over ten thousand different smells, could at least one of those detectable smells be that of our potential mates?

(14).

Poets have swooned over it since the invention of the written word; singers started crooning about it even before that time. It is the central theme in our daily lives, from the books we read to the people who make our hearts beat a little faster. Attraction to another individual is what insures any specie's survival. Certainly, a person smitten for the first time at a bar does not ask for genetic sequence and specifics about that special someone's immune system before approaching him or her. Yet perhaps some of that information is received and interpreted at a subconscious level, yielding all of the necessary information to trigger attraction. (8). Almost forty years ago, scientists Karlson and Luscher coined the term pheromone as a way of explaining the attraction within a species. (9).

Pheromones are chemical signals secreted by one individual and received by another individual of the same species, in which they trigger a specific behavior or developmental process. One of the hottest debates in the study of chemical senses is whether humans can produce and detect pheromones, and if so, whether they can use pheromone signaling to drive behavioral responses. The strangest behavioral data supporting pheromone - based communication in humans have come from work on menstrual synchrony. It has been shown, for example, that female college roommates begin to menstruate at the same time. Interestingly, this synchronization effect may be achieved solely by wiping underarm sweat from "donor" women onto the upper lips of "recipient" women, strongly suggesting that human pheromones may be contained in sweat. (10). So if our sense of smell is strong enough to coordinate and entourage of women who have never interacted to have the same menstrual cycle then it is arguable to say that our sense of smell has the same capability of attracting us to another individual sexually.

Humans, like other animals, emit odors from many parts of their bodies. Personal body odor represents secretion from several types of skin gland, most of which are concentrated in the underarm (axillary) area. The biochemical composition of these secretions (and the resulting individual body odor) depends on genetic, hormonal, metabolic, dietary, psychological, social and environmental influences. It is not known whether the olfactory signals from one individual's secretions are perceived consciously, and processed through the main olfactory system, or whether a portion of the signals are pheromones, which are presumably processed unconsciously through the accessory olfactory system. Some scientists believe that mammals usually (although not exclusively) detect pheromones through receptors found in a specialized structure called the vomeronasal organ (VNO). This is a small tubular structure lined with receptor cells, and it is close to the nasal cavity. Pheromonal information sensed by the VNO is transferred to the accessory olfactory bulb and other regions of the brain, including the anterior part of the hypothalamus. This region controls the neuroendocrine systems responsible for aspects of reproductive physiology and behavior. The NVO -to-brain pathway constitutes the accessory olfactory system, and it is distinct from the main olfactory system, the receptors for which are in the olfactory epithelium in the nose. (9).

Based on the fact that personal body odor represents a biochemical composition of genetic, hormonal, metabolic, dietary, psychological, social and environmental influences, it would appear plausible that we can "sniff out" our mate. After all we are animals. However, I would argue that our evolutionary development has made it so that we have surpassed the primitive nose as being the sole explanation for why we chose whom we choose as a partner. If we can use our sense of smell to find a potential mate, which includes that person having a desired genetic make-up which would ensure our survival, would this not exclude homosexual relationships as, in this combination there is no natural fertilization of one partner by the other? Yet, they are humans too and are attracted to one another. Would the theory of using our sense of smell to be attracted to another individual within our own species also exclude beastiality, a practice that is still done today and is postulated that Catherine the great died from in 1796? (12).

Indeed, one must always take into consideration the role of free will in attraction. Humans are complicated creatures whose actions cannot be simplified to suit one theory of rationalization for said actions. Scientist do not know for sure if pheromones contribute to mate selection in humans. Even if pheromones get the proverbial foot in the door; from there, the course of the relationship is controlled by many other factors, both conscious and sub-conscious.

References

(4).

WWW Sources

1) The Mystery of Smell: The Vivid World of Odors., Expresses sentiments about olfactory system

2)Mapping Smells in the Brain., Discusses codes in Olfactory system
3)How do We Smell?, Explains air flow in nasal cavity
4)What's that Odor?, Discusses receptors function in the nose
5)Science Year Kit, Explains smells and pheromones
6)Illusions Reveal the Brain's Assumptions, Brain makes an educated guess about what the information it receives is
7)Finding the Odorant Receptors, Discusses the function of odorant receptor
8) The Science of Attraction, Discusses pheromones and human attraction for one another
9)Human Pheromones: Communication Through Body Odour, Discusses the VNO
10)Evidence Found of Human Brain Detection of Pheromones, Discusses the possibility that the brain can detect pheromones
11) Role of Smell, Discusses how smell effects the other senses
12)Catherine II Empress of Russia, A Biography of Catherine the great
13)Olfaction, Explains how the olfactory system operates
14)Smell and the Olfactory System, Used for picture. It discusses the correlations between smell and the olfactory system


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