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Lecture 7

ANT211H5 Lecture Notes - Lecture 7: Foreplay, Parental Investment, Human Penis Size


Department
Anthropology
Course Code
ANT211H5
Professor
Sherry Fukuzawa
Lecture
7

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ANT211H5 FEMALE & MALE SEXUAL SELECTION
When did these qualities evolve and what is there adaptive value?
Documentary: the language of the body.
- Heavy cultural influence on what people perceive as “sexually attractive
In a Sociological point of view, we would ask ourselves “is there any reproductive or adaptive value to these
qualities?”
3 circumstances for a specific behaviour to have an evolutionary significance
1) Must be seen cross-culturally
2) Must have an adaptive value (must affect reproductive success)
3) Must be evident outside of our species (in our primate ancestors)
Female Sexual Selection (traits we look at)
body shape
WHR
asymmetry
breasts
menstruation
concealed ovulation
orgasm
menopause
Waist – hip ratio (WHR)
(Singh, 1993a) - tried to determine a sociobiological female body shape that was attractive to males across all
cultures (that had reproductive evolutionary value)
His studies began in Western culture:
He selected women who were generally considered attractive and measured their breasts, vs, waist, vs hips
He found:
Ratio of breast, hip & waist
“ideal” female figure cross culturally signals female reproductive status, reproductive capability & health
status
Typical range female: .67-.80; men - .80-.95
- there was a constant ratio within the range of .7
Was this a visual signal of potential fertility?
- There are many publications across different cultures testing his theory
Criticisms/limitations – Singh used line drawings
- However he discovered cross culturally that males found the ratio of WHR of .7 most attractive
Sex differences in Fat Distribution
Males – males exhibit when they express testosterone: “ android fat”: (WHR = .8-.9)
stimulates fat deposits more in abdominal region & inhibits fat deposition in thighs and buttocks
highly mobilized for energy
giving males different ratios between shoulders and waist

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metabolized very quickly
Women: when women express estrogen (when reaching sexual maturity): “gynoid fat”
inhibits fat deposition in abdomen & stimulates fat in thighs & buttocks - Distributed in hip/buttocks area
energy reserve for pregnancy & lactation - good energy storage for pregnancy and lactation (future
reproduction)
does not metabolize very easily
It’s proportion of their bodies that signifies fertility
KEY: not looking for an absolute measurements, but the ratio of measurements
Proportion of their bodies that signifies fertility
Problems with WHR-- limitations and exceptions
Studies in remote cultural groups where food is scarce (Yu & Sheppard, 1998)
In cultures with food resources that are scarce, girls with higher fat content = give off a higher visual signal
of higher energy and resources which they are able to pass on to their offspring
Energy storage is significant for birth, pregnancy
Doesn’t consider any other variables that have an influence on body shape
Symmetry (Gangstad, Thornhill & Yeo, 1994) – high levels of symmetry (left vs right)
- facial symmetry, signal of high genetic quality
Bilaterally symmetrical
Right and left sides are mirror images
Measure Facial Asymmetry – fluctuating asymmetry – diff between measurements in bilateral elements
Measuring 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
Experiments include activities where:
Digitized studies, and digitally skew and show face to male participants and ask which one is more sexually
attractive. Most males choose the most symmetrical face
Fluctuating symmetry= showing problems in development, someone of lesser genetic quality
Thornhill & Gangestad (1994); Grammar & Thornhill, 1994), Thornhill et al.,(1995) – series of studies of women who
had extra pair copulatory partners with males with symmetrical faces
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
Female orgasm is positive correlation with male symmetrical faces and during ovulation, they look for males
with higher testosterone markers
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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
faced) men
Reported more orgasms with EPC partners
More likely to have EPCs at time of ovulation (whole idea of short term sexual copulation opportunities with
males that have high testosterone genetic markers)
Is EPC Related to genetic quality of men? Extra pair copulations
Different female mating strategies those 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
Sexual partners:
Short term = genetic quality
Long-term = parental investment
Lactation & the breast – a lot of unique qualities in comparison to other female primates/mammals
Great variability among species in:
1. Anatomy of mammary glands
2. Composition of milk
3. Specific feeding behaviors
Female Breasts
Females in the human species maintain round, breasts and enlarged nipples even during ovulation
In primates: breasts will swell during ovulation, gestation and lactation, but deflate when not ovulating (visual signal
that they are fertile)
Why do human females maintain rounded breasts throughout ovulatory cycle?
In most human cultures female will supply entire nutrients to infant
Human Milk Composition – females provide all of the energy required for developing infant (for first 3 days of life)
Colostrum- 1st 3 days after birth before expression of milk, carries immunoglobulin’s, proteins, and antibodies that
mother will pass onto their infant to boost their immune system
Females can supply all the nutrients to their infants for up to a couple of years!
With the stimulation of nipples, milk production increases
Human milk is
Thin (than most mammals, quite low in proteins, signifies a continual nutrient source, demand feeing,
metabolize breatmilk very quickly)
Demand feeding: infants can feed every few hours whenever they want, because they metabolize nutrients
in the milk very quickly (short on calories)
Lactose, when not used up converts to fat, and is significant for brain development
Low concentration of protein & fat—hormones and digestive enzymes
High concentration of carbohydrates
Relatively constant nutritionally despite mother's own food intake
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