Transcript Assortment - University of Alberta

Female Choice
Limiting Resource
• Females
• Finite offspring production
• Intersexual selection
– “Female choice”
To Be Considered
• Male dominance and status
• Male resources
• Paternal investment (Dads vs. Cads)
Buss (1989)
• Cross cultural
• Women rank current resources, ambition,
and dominance (social status) highly
• Dominance and resources generally
positively correlated
Sadalla et al. (1987)
• Silent video of two men interacting in office
environment shown to female subjects
• More dominant male rated as having higher
status and being more attractive
• Actual attributes of each male controlled for
Theory
• Dominant males should produce more
offspring than submissive males
–
–
–
–
More access to females
Intra- and intersexual competition
Polygyny
Maximize inclusive fitness
Non-humans and Pre-modern
Humans
• Non-humans: this generalization seems to
hold quite well (e.g., Ellis 2002)
• Also, for pre-modern humans (e.g., Boone
(1986), Borgerhoff Mulder (1990), Voland
(1990))
• Problems with application to modern,
industrialized human populations
– Low socioeconomic classes have more children
than upper classes
Dominance
• Socioeconomic class may not be a good
measure of dominance
– Humans evolved in small social groups
• Mazur et al. (1984): West Pointers
– Graduation photos and rank 20 years later
– Dominants didn’t have more children than
submissives
• Modern contraception
Mazur, Halpern & Udry (1994)
• Redirected the question
• Do dominant looking males have more
opportunity for copulation than submissive
males?
• In pre-modern period this would likely
correlate with higher number of offspring
Method
• 3 year longitudinal study
• Male students, starting at grade 7 or 8
• Every 6 months
– Questionnaire on sexual experience
– Assessment of pubertal development
• Dominance rating based on school yearbook
photo
• Attractiveness rating
– Self and interviewer ratings
Results
• Most sexually active boys are more:
– Dominant looking, attractive, pubertally
developed
• Dominant boys tend to be attractive
• Dominant and attractive boys tend not to
wear glasses
• Dominance is the best predictor of sexual
intercourse
What Makes a Dominant Teenage
Male?
• Dominant faces
– Handsome or muscular
– Oval or rectangular in shape
– Prominent brow and chin
• Submissive faces
– Round (pudgy) or narrow (skinny)
– Less attractive
– Have glasses
Implications
• Dominance is the best predictor, although
attractiveness is also important
• No data here on female choice
– Are females attracted to dominant males?
– Do dominant males make their own
opportunities for sexual experience?
Bogaret & Fisher (1995)
• Variability in sexual behaviour
• Physiological, cultural, behavioural
explanations
• Between sexes
• Within sexes
– Often larger than between
Study
• Used 9 predictor variables
– Age, attractiveness, psychoticism, dominance,
social intimacy, male hypermasculinity,
testosterone, sensation seeking, sexual affect
• Recorded number of lifetime sexual
partners and number of partners in one
month from 215 male undergraduates
• Question: are some of the 9 variables
redundant?
Results
• Significant positive correlation between
number of lifetime sexual partners and:
– Positive sexual affect, antisocial tendencies,
physical attractiveness, sensation seeking, and
testosterone
• Age, sensation seeking, and testosterone
account for 25-30% of the variation
Townsend, Kline, & Wasserman
(1995)
• University age males and females with high
sexual activity
• Males with greatest number of sexual
partners were star athletes, fraternity
leaders, other high profile positions
Status
• Male success depended upon their status
being high and being known
– E.g., football and basketball stars had greater
access to women than rugby and lacrosse,
especially when football and basketball on
network TV
– Male’s best success was with female university
students who knew their status
– Wear varsity jacket to advertise
Status and Fitness
• Across species, link between male status
and fitness
• Symons (1979) argues females mating with
such males will achieve sons that will be
equally successful
• Success of university athletes in previous
study?
Scheib (1994)
• Hypothetical artificial insemination
– Decouples genetic from resource contribution
• Hypothetical dating service (for long-term
relationship)
Sperm donor
Mean Importance
Rating
Long-term mate
Heritability
Character
Health
Physical
Abilities
1.93
4.05
4.69
3.36
Heritability
• Physical, health, abilities, then character
• Character/personality not believed to be
passed by genes
• Value in long-term mate understandable, but
importance in sperm donor unexpected
• Possibility that it is very difficult to
decouple psychological mechanisms of
long-term choice in sperm donor context
Age & Status
• Buss (1989)
– Preference for males 3.42 years older
• Male RV
• Resources
• Gangestad & Buss (1993)
– Slight negative effect on female preference
for physical attractiveness
– The more wealth men can acquire, the less
important looks are
Bereczkei & Csanaky
(1996)
• Hungarian data set
• Couples with older, higher
educated husbands and
younger, less educated wives
had significantly longer
marriages
Age difference
at marriage
Younger husband
No age difference
Older husband
Mean number
of children
1.68
1.85
1.91
Age
difference
(years)
-27
-15
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
22
Percent
0.1
0.1
0.2
0.1
0.4
0.1
0.1
0.3
0.6
1.1
0.6
1.1
2.5
3.7
8.0
8.4
14.1
11.5
12.3
7.6
6.7
5.1
3.4
3.3
2.4
1.5
0.8
1.2
0.6
0.1
0.4
0.5
0.1
0.1
0.5
0.1
11.4%
- female older; + male older
Female
age at
Marriage
17
18-20
21-23
24-28
>28
Mean age
difference
(years)
-5.21
-4.25
-3.11
-2.41
-5.13
Hopcroft (2006)
• Status and reproductive success
• Potential fertility
– Reported rates of sex
• Achieved fertility
– Number of biological children claimed
• United States, General Social Surveys
(1989-2000)
Results
• Income increases frequency of sex for
males, but not females
• Education decreases potential and achieved
fertility for males and females
– But, better educated men have more children
than better educated women
Conclusions
• Income increases male/female differences
and education narrows male/female
differences re: fertility behaviour
• Income, for males, at least may translate to
proximate and ultimate reproductive
success
– Extremes (very poor and very rich) excluded
from this study, though
Testosterone
• Believed to be immunosuppressant (Kanda
et al. 1996)
• Handicap principle
• Male facial features may be honest signal of
genetic fitness
Conflict
•
•
•
•
High testosterone males
Good genes
Higher number of sexual partners
Low(er) parental investors
Mazur & Michalek (1998)
• Measured testosterone in military men
• Testosterone levels drop at time of marriage
• High testosterone males have less stable
marriages
Gray et al. (2004)
• Compared testosterone levels in males in
different relationships
• Single males had higher testosterone levels
than those in established relationships
• Suggests testosterone drops in long-term
relationships to promote pairbonding
Waynforth, Delwadia & Camm
(2005)
• Facial photos of 45 men
• Measures of facial features (e.g., jaw,
eyebrow ridge) influenced by testosterone
• Women rated photos for attractiveness
• Only women interested in short-term
relationships (higher sociosexuality scores)
showed preference for facial masculinity
• Most preferred less testosterone-driven face
Meaning…
• Some support for handicap principle
• But, handicap interpretation not the only or
the most significant factor in female choice
• Changing testosterone levels in males given
relationship type complicates matter
Boothroyd et al. (2005)
• Examined male faces
• Female variables
– Their own attractiveness, phase of menstrual
cycle, in or out of a current relationship
• Interestingly, female preferences
explainable by maturity cues as opposed to
health cues
Multiple Motives Hypothesis
• Cunningham, Barbee, & Pike (1990)
• Female choice contradictory
• Want dominant, high status mature male,
but also want socially approachable,
nurturing characteristics
Dominant Males
• Good defense against other males
• Protection of female, mate guarding
• High aggression
– May be directed at female and/or offspring
• More likelihood of promiscuity/polygyny
Four Features
• Neonate
– E.g., large eyes, small nose area
• Mature
– E.g., prominent cheekbones, large chin, thick
eyebrows
• Expressive
– E.g., large smile
• Grooming
– E.g., high status clothing
Ideal Face
• Not an average
• Extreme neonate and mature features
combined to produce most attractive male
faces
• “Cute” and “rugged” simultaneously
• Elicits feelings of nurturance and respect in
women
Other Body Attributes
• Want dominant, but not too dominant
• Various features besides facial representative
• Graziano et al. (1978)
– Even tall women prefer men of medium as opposed to
short, or very tall height
• Horvath (1981)
– Women prefer moderately-broad to non- or very- broad
shoulders
• Lavrakas (1975)
– Female preference for fit, but not extreme male
physique
Female Alternatives
• Good genes
– Dominant, masculine
– “Cads”
• Good paternal investment
– Willingness to provide resources
– “Dads”
Dads
• Schmitt & Buss (1996)
• Demonstrate helpfulness, honesty, kindness,
sensitivity
• Good communication skills
• Invoke love and show commitment
• Display resources and/or show potential for
long-term resource stability
Cads
•
•
•
•
•
•
Buss & Schmitt (1993)
Machismo
Provide immediate resources as gifts
Dominance displays
Show-off
Don’t have or won’t invest for long-term
Options
• Secure a Dad
– Gain resources
– May not be best genes
• Extrapair copulations (EPCs)
– Mate with Cad
– High quality genes
Concealed Ovulation
• Human females lack obvious signs of
estrous, unusual within the primates (Domb
& Pagel, 2001)
• Most primates (and other mammals) only
mate when females are likely to conceive
Theories
• Promotes paternal certainty (Alexander &
Noonan, 1979)
– Male forced to mate guard and mate with a female
frequently
• Promotes paternal confusion (Hrdy, 1981)
– Many males mate with female and any could be father
of offspring; reduces infanticide
• Reduces risk that self-aware human females will
use contraception to avoid risks of pregnancy
(Burley, 1979)
• Benefits females by allowing for EPCs with
higher quality males
Female Reproductive Cycle
• Normally ovulating women fertile for 6-7
days each month
• Sperm can survive for several days in uterus
• Hours after ovulation, conception no longer
possible
• Females will, however, have sexual
intercourse throughout their reproductive
cycle (i.e., non-reproductive sex) (Bellis &
Baker 1990; Baker & Bellis 1995)
Female Sexual Desire
• Continuous receptivity, but changing sexual
desire across the cycle
• Sexual desire peaks in mid-to-late follicular
and periovulatory phases of cycle (Regan
1996; Slob et al. 1996)
• With increased sexual interest mid-cycle,
might predict increased frequency of
female-initiated sexual intercourse at midcycle
Female EPCs
• Baker & Bellis (1995)
– Women with long-term sexual partner
– 6% reported last sexual intercourse with
extrapair partner
– Frequency of EPC was three times more likely
to occur at mid-cycle
• Gangestad et al. (2001)
– Females more likely to fantasize about extrapair
partner at mid-cycle
Implication
• Females adapted to mate when most likely
to conceive
• Females in long-term relationships are more
likely to engage in EPCs when most likely
to conceive
• Risk of getting caught?
– …Heading off on a bit of a tangent here…
Gangestad & Cousins (2001)
• Low FA men rated as attractive only by
women interested in casual sex
• For long-term relationships, these same
women did not find low FA men more
attractive
• If low FA correlates with higher genetic
fitness, offers support for idea of females’
use of traits to identify good gene providers
Low FA Males as Mates
• Various studies show that low FA males
may make poor long-term mates
• Have more female partners, produce more
offspring, more dominant, more likely to get
into fights, etc. (Waynforth 1998;
Gangestad & Thornhill 1997, Furlow et al.
1998)
• But, might be very good candidates for
short-term mates (i.e., Cads)
Scent Cues
• Several replications (e.g., Gangestad &
Thornhill 1998; Rikowski & Grammer
1999, Thornhill & Gangestad 1999)
• Men wear t-shirt for several days
• Women sniff shirts and rank smell for
attractiveness, sexiness
• Correlate ratings with point in women’s
cycles
• Mid-cycle women show greater preference
for low FA males’ scents
Perrett et al. (1998)
• Perrett et al. (1998) found Scottish and
Japanese women have preference for
somewhat feminized faces
• However, Penton-Voak et al. (1999) showed
that this preference breaks down at midcycle; then women show preference for
highly masculinized face
Implication
• Women are being attracted to higher quality
males when most likely to conceive
• Shift in Multiple Motives Hypothesis across
menstrual cycle
• Female choice adapted to optimize female
reproductive success both in terms of
genetic fitness of offspring and paternal
investment