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Lecture 10

ANT211H5 Lecture Notes - Lecture 10: Abdominal Cavity, Sexual Stimulation, Menstruation

Course Code
Sherry Fukuzawa

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Female Sexual Selection
Females compete with each other in some area to attract mates competing to require resources for their
offspring. This is true because females give a greater parental investment than males.
oMales tend to give parental investment, at least through the critical period.
oLimerance tend to give large series of resources during the first 2-4 years of the offspring life.
oMales tend to have a larger selection (“choosier”) for long term banks
Physical attraction is important component for males
oParticularly for short term mates, but also for long term mates.
oThis plays to the adaptive idea that males are choosing for their advantage.
oIt was more prevalence in male mate selection than female mate selection.
body shape
concealed ovulation
What constitutes physical attractiveness?
- Cultural influences
- Arbitrary taste
oFrom a sociobiological view, there has to be a connection to reproduction.
oIf mate choice has an adaptive value, therefore it must be related to reproduction individuals
should be choosing traits that signify optimal maturaity in order to have an adaptive value.
- Survival and reproduction?
Waist hip ratio (WHR)
(Singh, 1993a)
Ratio of breast, hip & waist
oWHR – waist hip ratio
oHe looked at populat media images of what in general males found attractive
oHe took measurements of body dimensions.
oWhat he found is that in the Miss America constant for the last 10 year, he found tat the winner had
WHR 0.7-0.69 ratio. He found this consistently in the Miss America pagent winners.
oThen he looked at Playboy center polls, and found that there was a continuity of WHR of about 0.7.
“ideal” female figure cross culturally signals female reprod status, reprod capability & health status
Typical range female: .67-.80; men - .80-.95
oSuggested that this particular ratio of WHR must represent an ideal female attraction to males. He
suggested that this is an indicated optimal fertility in these females.
oHowever, absolute dimension doesn’t matter- it is the ratio to the waist to the hips
oThis distribution of fat is in relation to gynoid fat (a fat found in association with estrogen). When
females release their secondary sex hormone, they start to produce this gynoid fat, which tends to
deposit in the of the buttocks, abdomen, and thighs. He found that it is related to energy reserves
that are required for pregnancy and lactation in females.
oThis is gynoid fat is very difficult to reduce (not metabolized easily).

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Sex differences in Fat Distribution
Males – testosterone: “ android fat”:
Stimulates fat deposits in abdominal region & inhibits fat deposition in thighs and buttocks
Highly mobilized for energy
Found that with the expression of testosterone, males tend to depoid android fat. This stimulates a fat in the
abdominal region, and inhibited the deposition of fat in the tight and buttocks.
Unlike gynoid fast, android fat can be easily metabolized (i.e., they can loose this fat easier).
The optimum range was about 0.8-0.9 an indicator of physical health in these males
oFemales choose males with a WHR of 0.8-0.9 as an indicator of better physical condition.
Women: estrogen: “gynoid fat”
Inhibits fat deposition in abdomen & stimulates fat in thighs & buttocks
Energy reserve for pregnancy & lactation
Problems with WHR
Studies in remote cultural groups where food is scarce (Yu & Sheppard, 1998)
Doesn’t take into account other variables in mate selection
WHR differs from 0.7 in the choice of females resources scare cultures
oCultures in which food can be quite scarce, males have been shown to prefer females with larger
WHR (large hips and buttock). This is because females are demonstrating greater energy reserve
when there is a food shortage, which is also good for fertility.
WHR, a lot of methodology of Singh is based on drawn images in which males choose with one is the most
attractive. So, there are a lot of other variables that are not taken into consideration.
Symmetry(Gangstad, Thornhill & Yeo, 1994)
bilaterally symmetrical
oThe amount of symmetry is often an indicator of genetic quality in body symmetry as well as
facial symmetry.
right and left sides are mirror images
oA lot of the research looks at movie stars and models
Measure FA – fluctuating asymmetry – diff between measurements in bilateral elements
oThe difference in any bilateral measurement
oAsymmetry – measurement of the difference of bilateral measurements
oMeasuring lack of symmetry
High levels of symmetry are thought to be indicative of hi levels of developmental precision
Inferred to possess good genes
Resistance to parasites
Females tend to have greater or more frequent orgasm with sexual partners with low fluctuating symmetry
Females also tended to engage in more extra pair copulations with males who are more symmetrical. Also,
they also reported to have higher frequency of orgasms. And these males were more sexually attractive
than their males.
Thornhill & Gangestad (1994); Grammar & Thornhill, 1994), Thornhill et al.,(1995)
opposite sex attractiveness - correlated negatively with FA
Attractiveness correlated positively with facial symmetry
negative correlation between the self reports of female orgasms & measures of FA in their partners

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Baker & Bellis (1993)
(EPC – extra pair copulations)
women engaged in extramarital affairs were more likely to have affairs with more attractive (symmetrical)
Reported more orgasms with EPC partners
Idea of tradeoff with extra pair copulation and maintaining long term
Is EPC Related to genetic quality of men?
-different female mating strategies that work in parallel
1. strong preference to find committed male with commitment to time & resources for her future offspring
2. motivated by mechanisms that facilitate impregnation by males of high genetic quality
Lactation & the breast
Great variability among species in:
1. Anatomy of mammary glands
2. Composition of milk
3. Specific feeding behaviors
Human Milk Composition
- Colostrum
o1st 3 days after birth
- Human milk is
oLow concentration of protein & fat
oHigh concentration of carbohydrates
oRelatively constant nutritionally despite mother's own food intake
- In western culture, many men find the size and shape of breast and nipples to be attractive
- In general, breast size will increase during ovulation this differs from other majority female mammals
- Breasts have taken on a new erotic sexual signal in modern humans
- In modern humans, we don’t actually produce milk right away, instead produce colostrum (thin, fluid, rich in
nutrients, essential fatty acids, etc.)
- In general, human milk is unique in comparison to other mammals it is thinner than skim milk. It is low in
fat, and calories.
Human female breasts are unique
- Placement of significant amounts of adipose tissue around the glandular tissue
- Maintain through the ovulatory cycle
-Why are human breasts enlarged?
-Why are they considered erotic?
Breasts are erotic attractors
Morris (1967) (Pair bond theory with hypersexuality)
Suggested that our unusual enlargement and colour of breast and nipple, all act to mimic secondary sex
trait. This acts as sexual signal to attract male partner.
Also suggested that the change of color and size of nipples acts as a visual signal to males for ovulation and
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