Outline Lecture 11 Mating 1
A: Some basic predictions
1. What would an outside observer predict about human mating?
2. “Would you…”
-men and women similar on going on a date
-much more men than women say they would go back to apartment (70-8%)
-same thing with gong to bed with the person
3. Basis of Predictions:
– Differences in minimal parental investment: who has the bigger gamete? (sperm vs.
– female carries offspring till birth (9 months), minimum is higher for females
– Biased “Operational Sex Ratio” (this is different from sex ratio)
– sex ratio: males:females
– OSR: number of males:females who are able to reproduce at that time
– sometimes females are not able, at some time there will be more males:females who
can reproduce at that time
– in some species, minimal parental investment is more for males (seahorses)
- Sex differences in body size and/or weaponry: males may have bigger bodies and weapon,
on average human males are stronger and larger than females
- Delayed maturity in males: pays to wait a little, build more muscle, social status, etc.
Holding off and building up capital before the competition starts. In humans females
begin puberty years earlier than guys do.
– Sex differences in mortality & longevity:
external causes: take bigger risks (physical and social) to attract mates;
internal causes: short-term physiological versus despite long-term negative effects (e.g.
physiological costs of testosterone)
whether internal costs or external costs, men are taking bigger risks and dying more at
- Sex differences in willingness to engage in sex: male reproductive success (RS) increases
with each additional mate, whereas females do not gain as much from mating again;
Males benefit more from multiple mates and from mating again soon than do females;
Result: males in polygynous species are more willing to have sex;
In every region, men desired more partners over the next 30 years than women did
The Coolidge Effect: male refractory period decreases when a new female is introduced
males more ready to have sex with a new female than with the same femaled
B: Effective Polygyny (i.e. greater variance in male RS than in female RS)
-for long term relationships, both sexes invest alot
-sex differences in choosiness diminish for long term relationship; for one night stands
and dates, women are more choosy than men are.
-women have larger minimum investment, & so are more choosy for short-term
5. Causes – Polygynous versus monogamous marriages:
polygyny: 1 male multiple females
polyandry: 1 female multiple males
polygynandry: multiple females & males
Polygynous Temne of Sierra Leone: male reproductive success increasing with the
number of females married to male, he has more offspring with more females
U.S. Mormons: more wives mean more reproductive success
In many culture