lecture 16

Question 1

what are the 2 Effects of TTT on gender phenotype

Answer 1

A) Physical Features
- Bones and muscles growth/strength
- Voice deepening
- Body hair (facial, pubic, underarm)
B) Behaviors
- Sex drive (libido=sexual drive)
- Rough and tumble (aggressive) behavior

Question 2

in the middle of a menstrual cycle, what increases?

Answer 2

estradiol increases, which results in the release of an egg (ovaries)
in humans: ovulation
non humans: estrus

Question 3

most female mammals (dogs) only accept and make advances when in estrus.. how about human and non human primates?

Answer 3

sexual behavior is less governed by sex hormones/fertility
Still, human females initiate sexual activity more often at ovulation (Maybe because estradiol increases the sensitivity of pudendal nerve and lubricates the vagina)

Question 4

what are the effects of sex hormones on mating

Answer 4

Some male animals only mate when TTT is high
Human males TTT is key….after castration (removal of testicles that produce TTT), lose sexual drive

Question 5

what can low TTT result in for men for mating?

Answer 5

Low TTT can result in impotence (sex drive decreases, trouble keeping erection)

Question 6

Once male or human reaches what age does their TTT decrease?

Answer 6

Age 35

Question 7

Are there obvious biological differences between
Heterosexuals vs. Homosexuals?

Answer 7

NO
- there is no differences in genitalia
- no differences in sex hormones (no difference in TTT)

Question 8

What is the evidence that Homosexuality is “nature” vs. “nurture”?

Answer 8

HEREDITY (TWIN) STUDIES IN MALES:
Brothers of a homosexual MALE:
are you homosexual and do you have a twin brother?
what type of twin do you have?
is your twin brother also gay?
monozygotic twin: 52% is gay
vs. dizygotic twin: 22% is gay
vs. adopted brother: 11% is gay
- there is a genetic component

Question 9

is homosexuality ALL genetic?

Answer 9

NO because then monozygotic twin would be at 100%
- additional nurture factors (different friends)
- maybe you dont know your twin brother is gay or gay brother is repressing

Question 10

which sex has a larger Sexually dimorphic nuclei in hypothalamus?

Answer 10

Heterosexual male larger than > heterosexual female (2x) (human and non human)

Question 11

what does the Simon Levay study show?

Answer 11

measured the size of nucleus in men vs female:
found that:
16 hetero MALE: size = 0.12 mm3
6 hetero FEMALE: size = 0.056 mm3
19 homosexual MALE: size = 0.051 mm3 (almost same size as females)

• CORRELATIONAL EVIDENCE