W6 L1 Sexual selection and human mate choice

Question 1

Darwin observation on gender differences

Answer 1

• Males, but not females, have armaments
• Males, but not females, are brightly coloured
• These ‘secondary sexual traits’ are not consistent with natural selection

Question 2

Darwin sexual selection theory

Answer 2

-not a struggle for survival but for reproduction right (loser doesn’t die but less/no offspring)
* Females(typically) improve their reproductive success by investing in quality offspring
* Males(typically) improve their reproductive success by investing in securing fertilisation success

Question 3

Mechanism of sexual selection

Answer 3

• intra-sexual competition, prevent other male from maiting or sperm efficiency (female doesn’t have much choice)
• inter-sexual competition, female choose

Question 4

Cause for Sexual selection competition in animal species

Answer 4

-Females have a greater ‘biological’ (gestation and lactation) investment in offspring, and thus should make a judicious choice of the sire of their offspring (cost of poor choice is substantial)
-Females are expected to base their choices on variation in male secondary sexual characteristics

Question 5

Do human have preferences in height study

Answer 5

-Have a diagram of couple, the only differences are in height. Rank which pair was most attractive
- showed that generally people prefer shorter female
-BUT tall female and shorter male prefer same height
-Study in UK: small positive correlation between female and male height w/ various

Question 6

Hadza of Tanzania – less exposure to popular culture

Answer 6

• Tanzanian hunter–gatherers
• live in savanna/woodland habitat
• women forage for plant foods
• men hunt with bows and arrows
• women ‘marry’ at around 17–18yr
• men ‘marry’ at approx. 20
• serial monogamy frequent
• females appear to exercise free choice of partner

Question 7

Study comparing low culture exposing population

Answer 7

• many Himba (Namibia) preferred partners of height equal to their own, and over 20% of men chose women taller than themselves
• men and women of the Yali tribe of West Papua (Indonesia) revealed little preference for any particular degree and direction of sexual dimorphism, suggesting that choice of partner is independent of body size
• men and women of the Datoga group (Tanzania) preferred extreme sexual dimorphism in stature, choosing men and women that were either much taller or much shorter than themselves

Question 8

Study on Psyc student on mate choice

Answer 8

-First year psychology female students asked to rank, for marriage or a date, target males with identical attributes (age, education, hobbies, income, etc) but noted the male had purchased either a Honda Civic or Porsche Boxster
- equal choice for marriage but more choose Porsche for date

Question 9

Preference herebility: genetic influence on mate choice

Answer 9

-study from mono and dizygotic female twin
-Some preferences that is heritable are: Kind & under-standing, healthy, physical attractiveness, exciting personality, earning capacity and good-house keeping
-can be influences by culture

Question 10

Study on human odor preferences

Answer 10

• our body odor are due to gene, coding for an immune fuction gene know as MHC
• people prefer different MHC but woman on pill prefer similar MHC
  -But preferences in MHC varies between study so there might be other factor acting

Question 11

Sexual selection in different gender

Answer 11

• Male reproductive success (number of offspring) was determined by the number of mating partners
• Female reproductive success was unrelated to the number of mating partners but resources transferences
  -study on drosophila so might not apply to human

Question 12

Parental investment theory

Answer 12

the sex that invests more in its offspring will be more selective when choosing a mate
the less-investing sex will have intra-sexual competition for access to mates

Question 13

Sexual selection and maiting rates in human

Answer 13

Reproductive potential > for males than females
* Gestation is approximately 9 months
* A male could potentially mate with hundreds of females per year; a man who is monogamous would likely have a single child with a given partner during that time period.
* In evolutionary currencies, this represents a strong selective pressure for males to mate multiply
- different culture have different models of reproduction

Question 14

Redoing bateman’s principle with mordern tech

Answer 14

• meta-analysis shows Bateman data could not be replicated

Question 15

Reason for Polyandry is taxonomically widespread and likely the ancestral state

Answer 15

• avoid reproductive failure (much more common in animals than typically recognized)
• material benefits (provision of ‘nuptial gifts’ or other nutrients transferred during copulation)
• genetic benefits (trading up, genetically diverse offspring)

Question 16

Incidences of polyandry in humans

Answer 16

• Of the 1,231 societies listed in the 1980 Ethnographic Atlas, 186 were found to be monogamous, 453 had occasional polygyny, 588 had more frequent polygyny, and 4 had polyandry
• It is associated with partible paternity, the cultural belief that a child can have more than one father
• Can also be associated with the idea that multiple sperm lead to a stronger child

Question 17

Maiting frequency does not equal offspring number

Answer 17

• Sexual selection may continue after copulation
• selects for male adaptations to ‘win’ at sperm competition (ie, greater investment in sperm production)

Question 18

Raffle in sperm selection

Answer 18

• Larger males produce more sperm
• Chimps have proportionally more sperm
• Suggests they have lots of competition

Question 19

Anatomical feature suggest monogamy in human

Answer 19

-if male are polyandrous, there would be more sperm competition, favoring large testes like chimp
-human are less than expected

Question 20

Study on male potential sperm-completion

Answer 20

Prediction: ejaculate should contain more and more active sperm under conditions of sperm competition
Methods: males, randomly assigned sexually explicit images involving either two males and one female (opportunity for sperm competition), or three females (no opportunity for sperm competition), provide ejaculates
-Results: Human males respond to different kinds of sexually explicit images, but not in a way predicted by sexual selection (opposite in fact)