Week 11 Smells like symmetry: the sent of love and attraction
From what we have learnt in our previous session, we now know that pheromone such as copulins or copulance fires signals to our brain that influences attraction. These signals are received through our nose; our sense of olfactory seems to have an even greater contribution to love, affection and attraction. In fact, the scent of dissimilarity in genes may play a direct role in influencing mate choice (Thornhill, Gangestad, Miller, Scheyd, McCollough & Franklin, 2003).
Humans produce individually unique body odours that are determined in large measure by the set of linked genes that regulate the immune system; this is known as the Major Histocompatibility Complex. The smells produced by the skin is such that each individual possesses a distinctive odour and possesses a mechanism for recognizing genetic similarity (Lewis, 1984).Today we will study odour prints, odours that carry unique genetic codes that determine how we perceive other people.
The uniqueness of odour prints stems from the MHC which allows us to naturally decipher genetic codes that initiate immune responses to guide us to a suitable mate selection (Thornhill et al, 2003). The MHC influences not just how perceptible we are to others, but may act as pheromones (Martins, Preti, Crabtree, Runyan, Vainius & Wysocki, 2005). Odours of the opposite sex are highly attractive, especially for males when females are in heat (Rasmussen, Lee, Roelofs, Zhang, & Daves, 1996). However, if humans use the odours of others, at least in part, to select a mate, then sexual orientation may influence preferences for human odours or production of these odours (Jacob, McClintock, Delano, & Oberg, 2002).
Acording to studies made by (Singh,2001) and (Thornhill et al, 2003), these sub groups can be divided into groups that produce odours that indicate fertility and those that do not. In experiments conducted by Thornhill et al, 2003, it was found that men displayed a significant sent preference for women who are at high risk of conception in their menstrual cycle. A predictable outcome of such experiments. What was interesting about this experiment was that women were found to be attracted to the odours of men that demonstrate traits of male body symmetry, this was especially true when women were ovulating (Thornhill et al, 2003).Who knew that body symmetry had a scent of its own. The odours we produce are altered accordingly to our bodily changes. For example, Individuals under stress or disease emit body odours quite different from their normal odours ( Filsinger & Fabes, 1985) this allows people to distinguish between healthy and appropriate mating partners. So you might find that you may be smellier when you are sick.
Our odour prints allow individuals to identify subgroups within the population, which suggests odour prints also have a role in social recognition (Singh, 2001). A reason for this was suggested by ( Leon, 1983) ,neural circuits in the olfactory system may develop a template to which odours can be neurally matched, allowing a unique responsiveness to meaningful odours. Over the years, this hypothesis was expanded upon by ( Filsinger & Fabes, 1985) who tested this theory on babies and the recognition of odours in motherhood. They found that newborn infants are more likely to orient to odours donated from the breast of their own mother rather than another which suggests that the detection of differences in human body odours begins early in life (Porter & Winberg, 1999; Filsinger & Fabes, 1985).
Odour identification occurs between mothers and their children and are related to the recognition of genetic relatives. ( Filsinger & Fabes, 1985). As this helps one to identify offspring, the MHC’s role in kin recognition adds to the communication of mother-offspring attachment process. This form of communication is so strong that (Porter & Moore, 1981) found that siblings and mothers were able to correctly identify odours of clothes worn by their siblings and off- spring versus those of strangers. In addition, parents were able to discriminate between odours produced by two of their own children( Filsinger & Fabes, 1985). From this perspective, olfaction appears to facilitate mother-infant interaction to avoid the parenting of the wrong offspring ( Filsinger & Fabes, 1985).
On the flipside, maternal behaviour may be influenced hormonal changes that occur during pregnancy may produce a unique physiological state in the mother which makes her highly receptive to her young (Hofer, 1981). This happens by the altering of olfactory thresholds, thus allowing the free expression of maternal responses to occur. This capacity is found to be latent in non maternal adults, particularly males. I guess this is how nature responds to couples who do not wish to have children, by producing odours that encourage motherhood as babies too emit odours of their own. It was found in the same research that interaction and experience with newborns in close quarters facilitate these behaviours in these adults through the similar emission of smells ( Filsinger & Fabes, 1985). The exposure to specific maternal odours could imprint into the nervous system a special responsiveness to such odours experienced early in life. ( Filsinger & Fabes, 1985) resurrecting a sense of an affection.
The MHC and odours produced by our bodies are key elements to not just mate selection and reproduction, they also provide a type of “aroma-therapy” for parenting adults. It encourages certain maternal behaviours and helps identify our children. It is comforting to know that even our sense of smell has a role to play in identifying people and selecting appropriate partners as a natural defence.
References
Filsinger, E.E. Fabes, R.A. (1985) Odour Communication, Pheromones, and Human Families, Journal of Marriage and Family, 47(2),349-359.
Hofer, M. A. 1981 The Roots of Human Behavior. San Fran- cisco:W. H. Freeman.
Jacob, S., McClintock, M.K., Delano, B. Oberg, C. (2002). Paternally inherited HLA alleles are associated with women’s choice of male odour. Nature Genetics, 30, 175–179.
Leon, M. 1983 “Chemical communication in mother-young interaction.” In J. Vandenbergh (Ed.), Pheromones and Reproduction in Mammals. New York: Academic Press.
Lewis, R. 1984 “Practice catches theory in kin recognition. Science 223:1049-1051.
Martins, Y. Preti, G. Crabtree, C.R. Runyan, T. Vainius, A. A. Wysocki, C.J. (2005) Preference for Human Body Odours Is Influenced by Gender and Sexual Orientation. American Psychological Society. 16(9), 694-701.
Porter, R. H. and Moore, J. D. 1981 “Human kin recognition by olfactory cues.” Physiology & Behaviour 27:493-495.
Porter, R.H. Winberg, J. (1999). Unique salience of maternal breast odours for newborn infants. Neuroscience and Biobehavioral Reviews, 23, 439–449.
Rasmussen, L.E. Lee, T.D. Roelofs, W.L. Zhang, A. Daves, G.D.Jr. (1996). Insect pheromone in elephants. Nature, 379, 684.
Singh, P.B. (2001). Chemosensation and genetic individuality. Reproduction, 121, 529–539.
Thornhill,R. Gangestad, S.W.Miller,R. Scheyd,G. McCollough, J.K. Franklin, M. (2003). Major Histocompatibility complex genes, symmetry and body sent attractiveness in men and women, Behavioural Ecology, 14 (5), 668-678.
Attraction (Human Instinct)
