Sexual Orientation

What patterns of genital arousal do men and women exhibit?

Male and female sexual orientation looks different. Femals: aroused by both male-male and female-female sexual stimuli. Men: greater arousal to their prefered sex. -Hetero men: aroused by watch female-female. Homo men: aroused by watching man-man and homo women were more like hetero men in that they like fem/fem more than man to man. Hetero woman aroused by all types.

Explain the following aspects onogeny (orging) of sexual orientation? Heritability.

Increased frequency of the Xq28 genetic marker in gay men. Homosexual brothers were 2x more likely to share Xq28.

What four hypothesis have been put forward to explain why genes associated with homosexuality have not been eliminated by natural selection?

1. Kin SelectionL Altruism, in some cultures. Homosexuals increse the fitness of their close relatives fa-afine. 2. Anatgonistic pleiotropy: Gay genes may increase reproductive selections in heterosexuals. This is stronger on the mothers side. However, this finding failed to replicate in 6 samples with 2 of 6 significant in opposite direction. 3. Maladaptive Extreme: most quantitative traits follow a bell-shaped distribution, with most people having an average value, some high, and some low (height). Maladaptive extreme is the situation when having an average value for a trait is better than being on the tails of the distribution. Ex: Perhaps gay genes persist because having a good balance of straight and genes might be better than having a lot of straight genes or a lot of gay genes. 4. Heterozygous advantage: Individuals who have only one copy of the gay gene and one copy of its allele are heterosexual and average higher fitness (variation) than heterosexual with no copies of gay gene. (??)

What is the Kinsey Scale?

4 dimensions of sexuality are conventionally used to assess sexual orientation via the Kinsey Scale.

Sex Hormones

CAH, 2D:4D, animal studies, drugs for preventing miscarriage

Sexual behavior of the Sambia of Papua New Guinea

Older boys get oral sex from younger boys as they go through puberty to explore their sexuality, and receive the semen that they cannot produce.

Maternal immune hypothesis:

Our immune system recognize invaders through molecule called antigens. Mothers lack Y chromosome, when a male fetus (Y) enter bloodstream, her immune system reacts. HEr immune system recognizes Y as foriegn and produces antibodies to attack Y linked antigens that are directly involved in brain development and T production.

The Perirhinal Cortex

Part of the brain that is more masculinized in homosexual women than heterosexual women.

Sexual Orientation of the Sambia of Papua New Guinea

Percentage of male that are heterosexual same as are western society.

What are the different dimensions of the Kinsey Scale?

Self identifications Attraction Fantasy Behavior

What do the distributions of sexual orientation look like for men and women?

Sexual attraction is a discrete trait in males. Most men will fall either well toward the exclusively heterosexual or well toward homosexual end of the continuum. Sexual attraction a continous trait in female: Frequencies decreased as sexual orientation went from exclusive heterosexuality to exclusive homosexuality.

Fraternal birth order a

The more older brothers a man has, the likelier he is to be homosexual. Homosexual men with older brothers are significantly smaller at birth than are heterosexual men with older brothers. This difference in birth, some other consequence of differential fetal development leads to homosexuality.

INAH-3

approximately 2-3 times larger in heteosexual men as in women and homosexual men. INAH-3 appears to be related to sexual motivation. Not clear whether differences in the size or structure of this region directly result in sexual orientation.