Project Proposal
Bio 3B
Saddleback College
Spring 2010
The effect of the menstrual cycle on sexual selection for temporary and long-lasting relationships in Homo sapiens based on olfactory cues.
Cole Querry and Ken Tupper
Department of Biological Sciences
Saddleback College
Mission Viejo, California 92692
Males who have a favorable body odor have been shown to be selected more often by females since their body odor is linked to their bilateral facial symmetry, which denotes good genetics. Since the menstrual cycle affects the hormone levels in women we researchers hypothesized that women who are menstruating would be more susceptible to the odor of males who have a greater degree of facial symmetry. What links change in hormone levels to smelling body odor? You need to better link the two here College-aged women smelt and rated the attractiveness of a total of 8 T-shirts that were worn by men for a period of 24 hours. Then a second study was conducted where college aged women smelt 5 T-shirts that were worn by men for a 24-hour period. In this study, the women were followed for a month smelling and ranking the shirts once every week. Results indicated that the female subjects did select the individuals with a greater degree of bilateral facial symmetry significantly more often. However, the menstrual cycle did not have an effect on the amount of times the males with the greatest facial symmetry were chosen. The study also showed that there was no significant difference in female selection of males with greater symmetry when their degree of difference was within 1%.
Introduction
Physical attractiveness has become a biologically and culturally important construct, giving a meaning to the pursuit of the perfect mate. What some are unaware of is that these phenotypic traits of facial symmetry and body odor can be related to good genes. Evidence indicates that pheromones can be directly correlated to facial symmetry cueing a high mate quality. needs citation
Many cultures define beauty in different ways; however, all cultures show a considerable agreement that bilateral facial symmetry to be is attractive (Rhodes et al 1998). Facial symmetry corresponds with the symmetrical development through stages of development therefore exemplifying genetic success against stress and time this sentence doesn’t make sense(Rikowski and Grammer 1999). Females use these genetic characteristics as cues to ensure quality in a mate choice and during different periods of menstruation, women’s preference on a sexual mate and the level of commitment can vary (Gangestad and Thornhill 1998).This sentence should also be in the abstract linking hormones to mate choice
Based on favorable body odors of men, females should have a greater response to those pheromones and choose men with greater facial symmetry. Throughout the different stages of the menstrual cycle, women have fluctuation in the attractiveness towards men who they would sleep with for a short-term relationship and who they would choose for a long-term relationship, or mate. Since during the week of menstruation women have a peak in sexual desire (P.C. Regan 1996). It is believed that during these peaks they would put greater selection pressure on which individual they would choose for a mate.
Women should put more selection pressure on the individual that they will choose for a long-term relationship since this will be the individual who will be providing them with offspring. For this reason this study will look at women’s selection for short-term and long-term relationships. Where is the hypothesis?
The ideas here are good, but not well connected. it needs some cleaning up to look more like scientific paper. The sentences lack flow and are too colloquial.
Materials and Methods
Experimentation began within the month of February of 2010 and data were collected at Saddleback College and outside the school. Eight white t-shirts were purchased then washed with odorless Tide laundry detergent to ensure there are no external odors contaminating the olfactory response. After the shirts had been washed, they were transferred into the dryer using clean latex gloves and once dried, immediately sealed in a zip-sealed bag to prevent odor contamination. The male subjects (n=8) were given the shirts and had to wear their given shirt for a twenty-four hour period. Each male subject, prior to wearing the shirt, showered with odorless Dove soap and was not allowed to apply any lotions, deodorants, colognes, aftershave, or any other item that could alter their natural body odors. Once the twenty-four hour period was over, male subjects immediately took off the shirts and placed it back into the zip-sealed bags. On Tuesday February 23rd and Wednesday February 24th, 2010, female subjects (n=53) were asked to smell each of the shirts and fill out a questionnaire asking: to rank the shirts based upon favorability on a scale from one to ten, choose who they would settle down with (based on scent), choose who they would select for a one night stand, and ask if they were menstruating. If the female subjects were not menstruating, investigators asked a subject when there their last menstruation was. Data was analyzed, and chi-squared contingency table was constructed.
The second set of data were was collected through the months of March and April of 2010. you should mention here what you are testing….the effect of position in menstrual cycle on attractiveness rating Male subjects (n=5) participated by wearing new t-shirts freshly washed with odorless Tide detergent t-shirts for a twenty-four hour period. Once the shirts were prepared in the same manner as in the first study, experimentation began with male subjects bathing with odorless Dove soap and immediately putting on the freshly washed and sealed t-shirts. After the twenty-four hour period, shirts were placed in the sealed bag once again to be smelled by female subjects (n=9). Male subjects wore the shirt one twenty-four hour period per week in order to follow female subjects throughout a month span. The shirts were washed and sealed between every study to prevent odor contamination. The women were asked once per week to smell t-shirts and rank them on a scale from one to ten based on desirability. (were they asked to rank the shirts from most desirable to least desirable or were the shirts each given an arbitrary number?)Shirts were randomized each week to ensure no female subject had an influence on another’s recordings. Numbered from one to five, the shirts were tested by female subjects and the questionnaire was then filled out. Asking the same series of questions from the first set of data were asked tested: who would you choose for a one-night stand; who would you choose to settle down with; are you menstruating; and if no, when was your last menstruation. After the last set of data was collected, a chi-squared contingency table was constructed.
Lastly, pictures were taken of all male subjects from both studies in this experimentation (eight from the first set of data collected and the five from the second set of data). Pictures were taken at a straight-on angle and the program ImageJ (National Institute of Health, USA) was used to measure facial symmetry. Three measurements were taken using ImageJ: A1, A2, and A3. A1 measured from the middle of the brow to the far tips of the right and left eye; A2 measured from the tip of the nose to the outer tips of both earlobes; and A3 measurement was taken from the cleft beneath the nose to the outer tips of the right and left side of the mouth, as shown in figure 1. Measurements of for all subjects were then transferred into MS Excel and the ratios were then calculated finding in order to rank subjects based on with greatest facial symmetry. These results were then tested as to how they ranked based on the experimentation compared to the rankings done by the female subjects in both sets of data collection.
Figure 1. Three facial measurements (A1, A2, A3) represent bilateral facial symmetry.
Results
Ratio averages of the three facial symmetry measurements of each subject and selection percentage for the first study are shown in table 1. The male subjects with the greatest degree of bilateral facial symmetry were never significantly chosen more by the by the menstruating group then by the non-menstruating group for long-term relationships too convoluted, needs revision. In the first study the individual with the greatest bilateral facial symmetry was chosen for what? 55% of the time by the menstruating group. with a P value of 0.5711, this shows that There is no significant difference in the amount of times chosen by the menstruating group compared to the non-menstruating group (p=0.5711, test you used). The individuals with a degree of bilateral facial symmetry of 98% or greater had a P value of 0.2560 or greater. What does this mean?
Ratio averages of the three facial symmetry measurements of each subject and selection percentage for the second study are shown in table 2. In the second study the individual with the greatest degree of bilateral facial symmetry was only chosen by the menstruating group 46% of the time, with a P value of 0.6711 wrong format. In this study all the individuals had a degree of facial symmetry of 98% or greater and only one individual was chosen significantly more by the menstruating group over the non-menstruating group (P value= 0.0005, test). For short term relationships only one individual (which subject #)was chosen significantly more often by the menstruating group. In this study the menstruating group did not choose individuals with greater bilateral facial symmetry significantly more often then than the non-menstruating group. This whole section should be rewritten or revised. A graph of results should be included.
Discussion
Favorable body odor has been shown to be linked to a higher degree of bilateral facial symmetry, and a high degree of bilateral facial symmetry is linked to good genetics. Research has shown that women will have peaks in there degree of sexual desire (P.C. Regan 1996). Therefore in our this study we looked at if this peak in sexual desire would also affect their choice in male subjects causing the women to choose individuals with higher degrees of bilateral facial symmetry more often during this peak of sexual desire weren’t the females choosing based on scent not symmetry. However in our study it has been shown that the peak in sexual desire during the week of menstruation does not have an effect on the females’ choice of male mates for a long-term relationship.
In our first study there were two individuals who were chosen significantly more by the menstruating group. These two individuals did not have a high degree of bilateral facial symmetry and were very rarely chosen doesn’t this contradict the previous sentence. The same thing happened with these two individuals in this study for the short-term relationship Too colloquial. Therefore with a larger sample size of women this apparent anomaly may disappear. Therefore another study where there is a larger sample size would be beneficial to determine more accurately if the peak in sexual desire during the week of menstruation affects women’s selection based on body odor.
In the second study where we followed the same women for four weeks we only saw one individual who was chosen significantly more often by the menstruating group for a long-term relationship, but this individual also was not chosen often. However in this study we did see one individual who was chosen significantly more often for a short-term relationship, and who was chosen a significant amount of the time. This individual did not have the highest degree of bilateral facial symmetry but he was chosen a significant amount of the time. To elaborate on this study it would be beneficial to do an extended study where female subjects are followed for many months to see if they will choose the same individuals every time or more often then not when they are menstruating and on there peak time of sexual desire. Don’t just repeat your results, analyze them. Why didn’t you find a statistical difference?
In this study it was noted that when males are within 1% difference in the degree of facial symmetry there was no significant difference in the amount of times they were chosen for a long-term relationship or a short-term relationship. When the degree of symmetry is this close, the scent of males who have a greater degree of masculinity have a more masculine scent that is preferred by women (Cornwell, R. E. et al. 2004).
Subject#1 / Subject
#2 / Subject
#3 / Subject
#4
Average
Ratio
(%) / 97.96 / 97.18 / 96.58 / 96.54
Selection
Percentage
(Menstruating) / 0 / 0 / 12.5 / 12.5
Selection
Percentage
(Non-menstruating) / 6.6 / 0 / 8.8 / 2.2
Subject
#5 / Subject
#6 / Subject
#7 / Subject
#8
Average
Ratio
(%) / 96.00 / 96.48 / 98.58 / 98.97
Selection
Percentage
(Menstruating) / 12.5 / 0 / 25 / 1437.5
Selection
Percentage
(Non-menstruating) / 4.4 / 11.1 / 35.5 / 31.1
Table 1. Average ratio percentage and selection percentage of male subjects in study 1 for long-term relationships.Table captions need to be written above the table, and both tables need to be under results, not discussion section.
Subject#1 / Subject
#2 / Subject
#3 / Subject
#4 / Subject
#5
Average symmetry
Ratio
(%) / 98.58 / 98.97 / 96.48 / 98.68 / 98.07
Selection
Percentage
(Menstruating) / 38 / 12 / 12 / 26 / 12
Selection
Percentage
(Non-menstruating) / 36 / 14 / 4 / 25 / 21
Table 2. Average ratio and selection percentage of male subjects in study 2 for long-term relationships.
References: Literature Cited