18 19 20 Sexual Orientation

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18 19 20 Sexual Orientation
2015-03-02 12:56:33
sex and evolution
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  1. Kinsey scale
    • used to scale heterosexual and homosexual tendencies in four areas
    • self-identification
    • attraction
    • fantasy 
    • behavior
  2. sexuality stability in men
    • heterosexual more stable in self ID and behavior
    • homosexual more stable in fantasy and attraction
  3. genital arousal for men and women
    • men more aroused by preferred sex
    • women aroused my both male-male and female female stimuli
  4. Men and women - sexual attraction discrete or continuous?
    • men - bimodal. Consistent in extremes. 
    • women - steadily decrease from heterosexual to homosexual.
  5. variations in discrete traits is due to...
    • a single gene
    • it is monogenic
  6. variations in continuous traits are ...
  7. threshold traits
  8. heritability for sexual orientation
    lower than 1
  9. maternal immune hypothesis
    a woman develops "anti male" antibodies when she is pregnant with a male. These antibodies may attack and alter subsequent sons' brain, may mimic prenatal androgen exposure, or may attack and deteriorate tissues that produce testosterone
  10. brain structure - heter vs homo
    heterosexual men have a 2-3times larger hypothalamus than women and homosexual men
  11. Heterozygous advantage hypothesis
    heterosexual males who have one "gay gene" allele have increased fitness over heterosexual men with no gay gene.

    little support for this
  12. kin selection hypothesis towards homosexual
    homosexual men altruistically increase the fitness of their close genetic relatives.

    • does not explain presence in present large scale societies.
    • does not explain why would homosexuals still desire to mate? its costly and hurts their altruism
  13. antagonistic pleiotrophy
    gay genes are maintained because they have different effects in different bodies

    genes have different affects in different bodies
  14. 4 developmental processes leading to sex orientation variation
    • prenatal androgen exposure - for women too much, for men not enough androgens
    • fraternal birth order 
    • brain structure - larger hypothalamus hetersexual males than homo and women
    • polygentic trait - threshold for the many alleles making individual homosexual.
  15. pedigree evidence of genetic differences
    brothers of homosexual men are more likely to be homosexual
  16. heritability evidence of genetic differences
    twin studies show more heritability
  17. gene-sharing evidence for genetic differences
    XQ28 gene in males increases likeliness of homosexuality