Download Sexual Orientation

Sexual Development
Module 53
Sex Linked Traits
• For males, the smaller Y chromosome often does not contain a
corresponding gene segment to match the one on the X
chromosome.
• This means that a male can display certain recessive
characteristics as the result of having only one recessive gene
carried on the X chromosome of his XY pair.
• Traits determined by recessive genes on the X chromosomes
are referred to as sex-linked recessive characteristics
• Color blindness, baldness, hemophilia, Fragile X
Thanks
Mom!
Hormones & the Developing Brain
• At about 7 weeks, a gene turns on the production of
testosterone by the testes in males.
• Estrogen is produced in females by the ovaries.
• During 4th & 5th months, the fetal brain’s wiring is
influenced by these hormones.
– this is when one get’s “wired” male or female
ADOLESCENT SEXUAL
DEVELOPMENT
• Puberty – 2 year rapid
period of sexual
development ending
with reproductive
maturity
Intersex
• Intersex – born with intermediate or unusual combination
of male & female physical features.
• Born a Boy, Brought Up a Girl: The David Reimer Story –
watch this documentary to see what life was like for a boy
raised like a girl after a botched circumcision.
– (4 part series – 10 minutes each)
Consequences of Sexual
Behaviors
• Sexually Transmitted Infections (STIs)
– 2/3 of new infections in people under 25
– 39.5% of sexually experienced 14-19 year old females had an STI
– Overconfidence & combination of attraction & alcohol at times all contribute to risky
behavior.
• Americans have higher rates of teen pregnancy & STIs than
Europeans? What environmental factors contribute to this?
Factors Contributing to
Teen Pregnancy:
•
•
•
•
Minimal communication on birth control
Guilt related to sexual activity (makes
one less likely to be prepared)
Alcohol Use
Mass Media norms of unprotected
promiscuity with no repercussions
Factors Predicting to Sexual
Restraint:
•
•
•
•
High Intelligence
Religious Engagement
Father Presence
Participation in service learning
programs (volunteering to help
others)
Sexual Orientation
Sexual Orientation
• Sexual orientation—direction of a person's emotional
and sexual attractions
• Heterosexual—sexual attraction for the opposite sex
• Homosexual—sexual attraction for the same sex
– Gay—typically used to describe male homosexuals
– Lesbian—typically used to describe female homosexuals
– 3% of men, 1-2% of women
• Bisexual—sexual attraction for both sexes
– Less than 1%
• Questioning – unsure of their sexual orientation
Psychological History
of Sexual Orientation
• Psychologists agree that sexual orientation is not chosen or willfully
changed.
• 1973 – Homosexuality removed from the list of “mental illnesses”
by the APA.
• “Efforts to change sexual orientation are unlikely to be successful
and involve some risk of harm.”
• Compared to men’s sexual orientation, women’s tends to be less
strongly felt and more variable (erotic plasticity).
Biology & Sexual Orientation
• No evidence supports that certain environments make it more or
less likely a person will be homosexual or heterosexual
– (e.g., parenting, abuse, sexual experience)
• Many examples of other animals showing homosexual behavior
• Brain structure—differences found in tiny cluster of neurons in
the hypothalamus of homosexual and heterosexual men
– In homosexual men and heterosexual women, the cluster was only half the size as
in heterosexual men
– Same difference is found in homosexual sheep
– When straight women smelled a scent from male sweat their hypothalamus light
up. Same thing happened when gay men smelled the sweat. Straight men’s
brains had no reaction.
• Genetics—evidence from twin studies suggests that genetics
play a role
– 52% of identical twins, 22% of fraternal twins, 11% of adoptive brothers
– Changing one gene in a fruit fly can alter their sexual orientation
– Older-Brother/Fraternal birth-order - Link to having older brothers? See ABC
News Clip
Other General Findings
• Findings suggest a possible relationship among prenatal stress,
androgens, and the development of brain systems that play a role in
sexual attraction
• Children who are raised by gay or lesbian parents are as well adjusted
as children who are raised by heterosexual parents. They are no more
likely to be gay or lesbian in adulthood
• Sexual orientation is an early-emerging (as early as age six), ingrained
aspect of the self that probably does not change.
– See ABC News clip on Genetic Links to Being Gay.
• Male and female homosexuals are less likely than heterosexuals to
have followed the typical pattern of gender-specific behaviors in
childhood
• Once sexual orientation is established, whether heterosexual or
homosexual, it is highly resistant to change.
• Gays and lesbians can be found in every occupation and at every
socioeconomic level in our society.