6b. Sexual Selection: human attractiveness & mate choice Flashcards
In order to reproduce, traits must have evolved which…
allow us to DISPLAY and INTERPRET the quality of potential mates
What does attractiveness encompass?
The set of adaptations (physical and non-physical) that display mate quality
What does mate choice involve?
The appraisal of the attractiveness of potential mates
Women’s mate preferences
Low fitness variance (more concern with quality of offspring)
Quality of offspring can be achieved via (1) high investment/resources, (2) good genes
Long term - more emphasis on investment than good genes
Women’s mate preferences (Buss, 1989)
Study of 37 cultures with over 10,000 participants
For long-term relationships, intelligence + kindness rated top by both men and women
Women consistently rated economic resources as important
Why do women have a strong preference for high status males?
Signals resources and protection
Why do women prefer slightly older men?
Status increases with age
The importance of status
Women compete for men of high status
Men compete to gain status (at the expense of someone else)
Status signals resources and protection and to some extent genetic quality
Women’s preferences for physical attractiveness
Athletic prowess and height (signals ability to provide and protect)
Study on personal ads - taller men got more responses
However, extreme tallness is not attractive - related to health
Studies on facial symmetry
- Women prefer men with symmetrical features
- Women have relationships with men of similar levels of symmetry
- Men with lower levels of asymmetry have more sexual partners
- Facial symmetry particularly correlates with sexual success in men
- Women more likely to have affairs with men who are more symmetrical
Why is symmetry so important?
Genetic predisposition to be symmetrical (bilateral symmetry)
Both sides of a bilaterally symmetrical trait (e.g. face) are coded for by the same genes
Asymmetry indicates that something has gone wrong
Why does asymmetry occur?
Genetic reasons (animals with high levels of mutations have more asymmetry) Developmental reasons (e.g. parasites, pollutants, illness) Both disadvantageous to fitness Random deviations are called FLUCTUATING ASYMMETRY
Masculinity causes the formation of secondary sexual characteristics via testosterone…
square jaw
brow ridge
cheekbones
Testosterone is an immunosuppressant. What does this mean?
Vulnerability to infections and cancers
In order to have high levels of testosterone and stay healthy, what must a man have?
Good genes and development
When do females prefer masculinised faces?
When most fertile (as this is when genetic signals are most important)
Preferences for physical attractiveness are secondary to…
indicators of status and resources in women (particularly for long term relationships)
Priority of investment from men due to:
higher bi-parental care in humans
high resource cost of human offspring
Men’s mate preferences
Males are less choose - greater concern with quantity of mates
However, more parental investment than most species –> some choosiness
Choosiness also varies with extent of investment (one night stand vs. marriage)
May also vary with man’s own mate quality
Three primary selection pressures have shaped men’s mate preferences:
(1) The need to mate with women capable of bearing offspring (i.e. fertile, healthy)
(2) Importance of passing on good genes to offspring
(3) Avoidance of cuckoldry
YOUTH as an indicator of health and fertility
Youth is crucial because fertility declines with age
Cross culturally, men prefer women 2.5 years younger (ave.)
As men get older, they prefer increasingly younger women
BODY SHAPE as an indicator of health and fertility
Research has focused on:
- Waist-to-Hip Ratio (WHR)
- Body Mass Index (BMI)
Waist-to-Hip Ratio (WHR)
Female body is an hourglass shape
WHR - the diameter of the waist divided by the diameter of the hips
<1 = waist is more narrow than hips
Singh argued that WHR is more important than slimness
What is thought to be the optimal WHR?
0.7
Evidence for the role of WHR
WHR = 0.7 correlates with with general health and fertility
Singh argues related to optimal levels of oestrogen and resistance to certain diseases
Historically, women have used methods to alter WHR (corsets)
Body Mass Index (BMI)
BMI = weight / height squared
Cue to fatness/thinness
Study with photos of real women - attractiveness ratings fell as image got fatter, and fell sharply as it got thinner
WHR was a poor predictor of attractiveness
TRUE OR FALSE: WHR of 0.7 is optimal cross-culturally.
False - Hadza of Tanzania
Urban vs. rural society preferences (WHR vs. BMI)
Britain vs. Malaysia
BMI was primary factor
The more industrialised the society, the lower the BMI preferred
Other measures of sexual attractiveness (other than WHR/BMI)
Facial symmetry
Clear skin
Hairless body
Sexual ornaments e.g. large/symmetrical breasts, long/shiny hair
HOWEVER some of these can now be faked! E.g. shaving
Why are men are most concerned with physical attractiveness?
Signals health and fertility
Why are women most concerned with status?
Signals resources and protection
