Module 50: Sexual Development

Genetic factors

Males and females have differing sex chromosomes

Physiological factors

males and females have differing concentrations of sex hormones, which trigger other anatomical differences

X chromosome

the sex chromosomes found in both males and females. Females typically have two X chromosomes; males typically have one. An X chromosome from each parent produces a female child

Y chromosome

the sex chromosomes found only in males. When paired with an X chromosome from the mother, it produces a male child

testosterone

the most important male sex hormone. Both males and females have it, but the additional testosterone in males stimulates the growth of the male sex organs during the fetal period, and the development of the male sex characteristics during puberty

primary sex characteristics

the body structures (ovaries, testes, and external genitalia) that make sexual reproduction possible

secondary sex characteristics

nonreproductive sexual traits, such as female breasts and hips, male voice quality, and body hair

spermarche

the first ejaculation (usually happens in males by age 14)

menarche

the first menstrual period (usually happens to females by age 12.5)

intersex

a condition present at birth due to unusual combinations of male and female chromosomes, hormones, and anatomy; possessing biological sexual characteristics of both sexes

sex-reassignment surgery

to create an unambiguous sex identity for some children who are intersex

herpes

a viral infection, caused by a group of herpes viruses, that may produce cold sores, genital inflammation, or conjunctivitis

HIV

a life-threatening, sexually transmitted infection caused by the human immunodeficiency virus

AIDS

a life-threatening, sexually transmitted infection caused by the human immunodeficiency virus AIDS depletes the immune system, leaving the person vulnerable to infections

Communication about birth control

Many teenagers are uncomfortable discussing contraception with parents, partners, and Peers. But teens who talks freely and openly with their parents and with their partner in an exclusive relationship are more likely to use contraception

Impulsivity

Among sexually active 12-to-17 year old American girls, 72% said they regretted having had sex. If passion overwhelms intentions (either to use contraception or to delay having sex), unplanned sexual activity may result in pregnancy

Alcohol use

Among late teens and young adults, most sexual hook-ups (casual encounters outside of a relationship) occur after alcohol use, often without knowing consent. Those who use alcohol prior to sex are less likely to use condoms. By depressing the brain centers that control judgement, inhibition, and self-awareness, alcohol disarms normal restraints — a phenomenon well known to sexually coercive people

Mass media

Perceived peer norms influence teens’ sexual behavior. Media help write the social scripts that affect our perceptions and actions

High intelligence

Teens with high rather than average intelligence test scores more often delayed sex, partly because they considered possible negative consequences and were more focused on future achievement than on here-and-now pleasures

Religious engagement

Actively religious teens more often reserve sexual activity for adulthood or long-term relationships

Parental presence

Close family attachments also predict kater sexually initiation

Service Learning participations

several experiments have found that teens volunteering projects had lower pregnancy rates than did comparable teens randomly assigned to control conditions

sexual orientation

our enduring sexual attraction, usually toward members of our own sex (homosexual orientation) of the other sex (heterosexual orientation); variations include attraction toward both sexes (bisexual orientation)

Rates of homosexuality

According to more than a dozen national surveys in Europe and the United States, about 3-4% of men and 2% of women are homosexual

Anti-gay stereotypes

The prevalence of harmful anti-gay stereotypes can also contribute to the isolation and rejection that many nonheterosexual people feel (gay men are pedophiles)

Erotic plasticity

men’;s sexual drive and interests are less flexible and varying than are adult women’s

Kinsey Institute

investigators interviewed nearly 1,000 homosexuals ad 500 heterosexuals. Their findings: Homosexuals are no more likely to have been smothered by maternal love or neglected by their father.

Same-sex attraction in other species

Same-sex sexual behaviors have also been observed in several hundred other species, including grizzlies, gorillas, monkeys, flamingos, and owls

Gay-Straight Brain Differences

One hypothalamic cell cluster is smaller in women and gay men than I straight men. Gay men’s hypothalamus reacts as does straight women’s to the smell of men;s sex-related hormones

Genetic influences

Shared sexual orientation is higher among identical twins than among fraternal twins. Sexual attraction in fruit flies can be genetically manipulated. Male homosexuality often appears to be transmitted from the mother’s side of the family

Prenatal influences

Altered prenatal hormone exposure may lead to homosexuality in humans and other animals

Older brother (fraternal birth order effect)

Men with several older biological brothers are more likely to be gay, possibly due to a maternal immune-system reaction

Gay-straight trait differences

• spatial abilities

• fingerprint ridge counts

• auditory system development

• handedness

• occupational preferences

• relative finger lengths

• gender nonconformity

• age of onset of puberty in males

• face structure and birth size/weight

• sleep length

• physical aggression

• walking style