Gender and Sexual Development: Biological and Social Influences
Brewer & Hendrie
: F most often report CV during partners orgasm/intercourse Buss: attributes ranked equally = kindness/understanding, intelligence, exciting personality, creativity; M ranked physical attractiveness higher; M ranked desire for children where F ranked earning capacity Clark & Hatfield: date: 50/50 M/F; apartment? 69/6; sex? 75/0 (F are long term; M are short term) Denis, Afifi, & Granger: higher T = perceived risk in pillow talk; lower T = positive perception of pillow talk Hughes & Kruger: F engage/prefer intimate talking before/after sex more than M Schmitt et al: how many sexual partners over 30 years = avg. higher for M (6-8) F (2-3) CV research: F reported moan more than M partners. F: moan, give instructions, consistent satisfaction w/ vocalization. M: verbal vocalization, timing = own orgasm. No impact on fertility/relationship satisfaction. F w/ F = greater satisfaction w/ partners meaning/grunting than F w/ M. Reports of positive perception of partner’s CV. M = moan during own orgasm & verbal; F = give instruction during own orgasm & nonverbal Phenotypic Ms: Klinefelter (XXY/XXXY): learning dis. (lang), tall, small testes, gynecomastia, F-typical body, less hair, low T – inc. LH (lack of neg. FB), low sex drive, low sperm count Jacobs (XYY): undiag., tall, inc. growth rate, normal T, lower IQ, engage in criminal activity/antisocial Phenotypic Fs: Triple X: undiag., generalizations diff. bc only 1 X active (Barr) at anytime in F cells, explains mild effect; cog. def. = delayed lang. dev., lower IQ; fertility mostly normal Turner (XO): lack of normal ovaries, lack of gonadal hormones, no puberty, sterile, short, broad chest, webbing, cog. def. = visuospatial ability, memory, attention; treated w/ growth hormones/androgens to inc. growth & estrogens for 2nd sexual charact. Genital development: 4 weeks: undifferentiated “genital ridges”; 5 weeks: differentiation –> Ms: presence of SRY = testes leading to prod. of AMH/T; Fs: w/ exception of ovaries, proceeds in absence of genetic instructions; ovaries inactive prenatally, several genes involved in stim. ovarian dev + inhibiting testes development; 6 weeks: 2 ducts go from gonad to ext. site of genitalia; Ms = T stim. wolffian ducts which turn into epidid., vas def., ejac. ducts, sem. ves., AMH @ testes = Müllerian to regress; F = no AMH = Müllerian dev. into oviducts, uterus, vagina; wolffian duct regress in absence of T External genitals: identical genital tubercle (glans penis/clit), urethral folds (shaft/minora); genital swellings (scrotum/majora) (Ms must convert T to DHT for masc. of ext. genit.; feminization of gen. occurs in absence of hormonal signals) Genes: SRY absence = F default pathway; presence = testis genes (SOX9, WNT4, RSPO1, DAX1) SOX9 = promotes genital ridges turning into testes FOXL2 = suppresses SOX9; “safety valve”; defective FOXL2 results in intersex; Gene on Y for inc. stature; Y-linked genes involved in spermatogenesis; mice à brain/behavioral diff. influenced by genetic mech. not involving SRY & testicular hormones (unknown) Gonadal intersex: possessing ovarian & testicular tissue (one/both glands contains both); testicular tissue underdeveloped/ovarian tissue normal; F structures predominate so majority of affected are XX, minority chimera Non-gonadal intersex: AIS: mutation in gene for androgen receptors render insensitive to androgens (DHT); affects XY (gene is on X, Fs have another X); partial/complete; testes develop normally under SRY influence – prod. of AMH/T, but no effect so Wolffian duct arrested, default pathway proceeds; phenotypic Fs w/ no F-typical internal rep. structures; diagnosis: newborn (shallow vag., testes = lumps), puberty (lack of pubic hair, primary amenorrhea); complete AIS: indistinguishable from XX Fs, taller; treatment: gonadectomy to lower cancer risk, estrogen prevent osteoporosis, deepening of vagina, med. problems of AIS overshadowed by stigmatization, inappropriate. treatment, parental deception; 5-alpha-reductase deficiency: inability to convert T to DHT; auto. rec. trait; affects XY Ms — testes function normally, producing AMH/T; internal rep. tract normal, but ext. genitalia do not develop toward M; raised as daughters; effects rescued by surge in T during puberty where girls turn into boys; few traits are completely DHT dependent (hair); CAH (congenital adrenal hyperplasia): overproduction of precursor steroids by adrenal gland; rec. genetic. def.= lack of enzyme involved in corticosteroid production from precursor steroids; no neg. feedback = brain/pituitary glands signal for inc. precursor steroids –> inc. production of androgens from excess precursor steroid –> excess androgen causes masc.; sexual dev. effects only XX (raised as daughters); in XX, Müllerian develop normally; if excess androgen occurs early enough Wolffian can be rescued (both persist); more common for androgen excess to occur during ext. gen. differentiation (F genitalia = masc. enlarged clit, fusion of labia); treatment = lifelong admin. of corticosteroids, surgery to demasc. genitals, prenatal treatment in dev.; CNS: different androgen levels in XY & XX: Onuf’s nucleus: innervates motor neurons of pelvic floor (base of penis); larger/contains more neurons in Ms; Medial pre optic area (MPOA): anterior hypothalamus associated w/ M sexual behavior in rodents; in humans, the INAH3 part of the MPOA is larger in Ms than Fs SDN-POA in rats: analog is INAH3; F rats induced to dev. larger SDN-POA w/ T treatment; Ms induced to dev. smaller SDN-POA w/ castration only during sensitive period; T facilities the survival of SDN-POA neurons 1. Cerebral hemisphere sizes (XY Ms, R>L) 2. Amygdala(XY Ms use R>L, XX Fs use L>R) 3. Serotonin production (XY Ms > XX Fs) 4. Dopamine production (XX Fs > XY Ms) Mounting: adult F injected w/ enough T will mount receptive Fs; adult Ms castrated will stop mounting (activational) Lordosis: adult Ms castrated + given estrogen will not show lordosis; but, castrated early in development + given estrogen in adulthood, they will; Fs treated w/ T early in development will not show lordosis –> T levels in early dev. determine lordosis in adulthood (organizational) Sensitive periods: prepubescent monkeys engage in play-sex; Ms mount, but Fs treated w/ T in fetal life took on mounting role in play sex; affected nonsexual behaviors too (play fighting & rough play); Fs not treated during fetal life, but given T in adulthood did not show this behavior (organizational); primates have many sensitive periods; Fs not treated during fetal life, but given T in adulthood did show more M-typical nonsexual behaviors Aromatization hyp: rodents/birds –masculinization of brain by estradiol aromatized from T, not T; neonatal injection of estradiol can masculinize; blocking aromatization or estradiol receptors interferes w/ masculinization effects of T; genetic Fs protected from masc. due to alpha fetoprotein (deactivates circulating estradiol. but does not cross BBB); genetic Ms –> T enters brain, & is then converted to estradiol; not as apparent in humans for T to masc. brain; External factors: pregnant rats + forced immobilization or bright lights = demasculinized M offspring; admin. of sex hormones in pregnant humans causes higher risk for cervical cancer in early life, breast cancer in later life, fertility issues, rep. tract. issues; social/environmental = M rates raised in isolation = less likely to appropriately respond sexually to estrous Fs; also anatomical changes in brain organization Puberty: biological transition to sexual maturity; pubertal growth spurt begin/end earlier in Fs than Ms; leads to increase in height as well as changes in skeletal structure/body comp.; Delay in pubertal growth spurt in Ms account partly for them being taller than Fs (12 for F, 14 for M); puberty in started via pulsatile secretion of GnRH, stimulating gonadotropin (FSH & LH) & gonadal hormone secretion; body weight/body fat uses hormonal signals to trigger hypothalamus to initiate pubertal maturation (leptin = peptide hormone secreted by fat cells; leptin stimulates secretion of kisspeptin (signaling molecule); kisspeptin stimulates secretion of GnRH, triggering puberty (body fat -> leptin -> kisspeptin -> GnRH -> gonadotropins -> gonadal steroids -> target tissues); Sex hormones have organizational effects at puberty –> evidence from imaging: Ms & Fs brains appear to diverge at puberty; estrogen drives dev. of parahipp. cortex, involved in memory & Fs > Ms in terms oof size & memory related tasks; process of sex.diff. appears to be put on hold during childhood, to be cont. towards completion w/ T & estrogen levels rise during puberty; Ms: growth of penis, pubic hair, auxiliary hair, voice deepens following enlargement of testes; eject. + nocturnal emissions; Fs: breasts, growth of armpit hair, pubic hair, growth/maturation rep. tract + external genitalia; onset of menarche (starting younger in western countries likely due to change in diet w/ cheap, calorie-rich manufactured foods
Gender: entire collection of mental/behavioral traits that differ btwn sexes (“gendered” traits: gender identity, sexual orientation, verbal fluency)Mary Wollstonecraft – Vindication of the Rights of F (1792) during a time when most people believed that only M were capable of performing the duties required for public life; some scholars disbelieve gender diffs. exist or attribute existence to societal not biological influences; 2005: Harvard Prez. suggested few F enter physics due to biological diffs. btwn sexes, leading to his resignation 2006; 2017: Google engineer suggested same regarding tech Cognitive traits: visuospatial: mental rotation (M outperform F; seen w/ navigation strategies (compass vs. landmarks); object location memory: F outperform M; verbal skills: F list more words than M; Personality traits: M more likely to show amore aggression than F (physical/verbal/written aggressiveness), M more likely than F to commit violent crimes; F more likely than M to express aggression indirectly via nonphysical means (malicious gossip); interests: M more likely than F to have thing/object related interests while F more likely than M have people/occupation related interests; Attitudes towards sex: casual sex: M express more permissive attitudes than F (pattern observed in over 50 countries; Esquire 2007 asked how you would feel after casual sex encounter: “satisfied” M >>> F; “regret” F >> M; choice of sexual partner: F more likely to be attracted to older partners; M more likely to be attracted to younger partners; F more interested in partners’ social status/wealth; M more interested in partners’ physical attractiveness (same pattern observed in Chinese cultures); jealousy: M & F both experience jealousy w/ F more likely to experience emotional jealousy & M more likely to experience sexual jealousy Gender diff. arise early in life: 3 to 4 month old infants know diff. btwn M & F typical faces; 6 months can distinguish btwn M-typical & F-typical voices; 2-3 years of age, children develop sense of own sex; before 3 years, children are unable to grasp that sex is a fixed attribute (gender constancy at 3-4 years of age); sex diffs. appear prenatally (fetal life); toy preference begin to diverge at 18 months: boys prefer vehicles, weapons, balls, construction while girls prefer dolls & play kitchen; by 4 years of age, children mostly play w/ other children of the same perceived sex (moral rules: boys governed by rules of justice while girls play by rules of social conventions); diffs. in cog. skills emerge around 9-12 years old (boys higher scores in calculating & mental visuospatial tasks (mental rotation) begin to appear); at 14, boys higher scores in problem solving tasks become evidence (does not translate to better grades, girls get better grades) Evolutionary forces: diffs. in cog skill: result of sex diffs. in division of labor over time such that Ms have taken leading role in hunting, warfare, & exploration (traits shaped by selection = proficiency in visuospatial tasks, navigation, etc) whereas Fs have taken leading role in home activities (traits shaped by selection. = greater hand & finger dexterity, object location memory, verbal ability, etc); diffs. in attitudes towards sex (causal sex) = Ms greater interest in casual sex is explained by their minimal biological investment in offspring; Fs lesser interest in causal sex is explained by their high levels of investment in offspring); diffs. in jealousy: Ms sexual jealousy is the evolutionary result of uncertainty of paternity; Fs are always certain of maternity, but Ms can never be certain; in humans, both parents invest great amounts in offspring (mother = dependent on father to provide resources & help; father needs to make sure all his investment is into offspring that is actually the father’s) Bio. factors influ.gender: CAH: evidence that hormones influence sex diffs. in traits & behavior – XX CAH Fs who are exposed to elevated levels of androgens during fetal development, exhibit some behaviors that are shifted in the masculine direction; same tendency observed for visuospatial tasks (mental rotation); 5-alpha-reductase deficiency: XY Ms affected appear phenotypically F at birth despite their prenatal T exposure (no DHT), but masculinize at puberty; most affected raised by parents as daughters as identified before puberty; at or soon after puberty, their gender identity shifts from F to M, indicating role for T both during prenatal & pubertal dev. for gender; unaffected children: XX fetuses: the lower the level of prenatal T, the more likely they would prefer “girl toys” over “boy toys” in childhood; marker in adults reflect prenatal androgen exposure 2D:4D ratio: index finger tends to be longer in XX Fs than XY Ms –> 2D:4D ratio used as index & the ratio is lower in XY Ms (high T) & higher in XX Fs (lower T); evidence ratio is influenced by prenatal androgens: fetal T levels: high T = low 2D:4D ratio [XX Fs w/ CAH: lower ratio; XY Ms w/ AIS: higher ratio; XX Fs who were members of opposite sex twin pair = lower ratio than members of both XX-F twin pairs; admin. T to pregnant rats = offspring ratio lowered] Otoacoustic emissions (OAEs): sex diffs. in auditory system exist; the cochlea generates sounds (SOAEs = spontaneous; COAEs = cicl-evoked); XX Fs generate more & louder OAEs than XY Ms & diffs. also exist in monkeys & sheep –> evidence that OAEs are influenced by prenatal androgens: F sheep exposed tov higher than normal levels of T have weaker COAEs in adulthood; XX Fs who are opposite-sex twin pairs have weaker COAEs & SOAEs compared to XX Fs who are same-sex twin pairs Life experience influence gender: the primary social influence on gender is family (dressing them, decorating room, type of toys); reinforcement of behavior, activities,/games –> “acceptability” is left up to subjective definition; influence can also be exerted without much conscious effort (i.e., role models); children who have older sibling of same sex are more gender typical than children who have opposite sex older sibling: PSAI score: higher = M typical, lower = F typical [genotypic sex is stronger predictor of gender-related traits than influence of older siblings] Media –> offers children things to imitate in gender domain: role modeling: when shower films, children were found to attend more to characters of the same sex as them; “Notes” study: exposure to broadcast media played a marked role in promoting gender stereotypes; today –> can be argued that media is promoting less gender stereotypes than the 1970s; in 1960s, fem. movement initiated resistance against F roles in society & many map rents made efforts to de-emphasize gender stereotypes in raising children; more F representation in school, college, & sports (changing definition of “athletic”); language= reinforces gender via grammatical structure & verbally communicated rules (children speaking lang. w/ grammatical genders tend to be rare of own sex 1 year earlier than children speaking languages without grammatical genders; gender learning from sociocultural rules = “big boys dont cry”, “man up”; socialization is a powerful influencer of gender development, but it is not everything –> there are children that are resistant to the socialization of gender, despite exposure (e.g., children who grow up identifying as gay, transgender, etc; socialization cannot negate biological influences (e.g., David Reimer = botched circumcision; penis destroyed; under advise from John Money, parents renamed him Brenda & raised him as a girl; genital recon. at 2; estrogen treatment during puberty; never adopted a F gender identity; hated his breasts, always attracted to F; underwent sex reassignment via phalloplasty, double mastectomy, & T treatment; married & had children; committed suicide) Gender dev. involves complex interactions: nature & nurture interact in the dev. of most gendered traits; life experience & genes interacts in complex ways to influence antisocial behavior in M: the victim-perp cycle says that people (esp. XY) w/ history of sexual/physical abuse during childhood are more likely to commit antisocial acts later in life; MAOA gene: normally regulates dopamine & serotonin; 2 versions: fully active & less active; possessing one or the other version alone: no effect on antisocial tendencies; but less active form + severe childhood abuse = 85% chance of antisocial behavior in adulthood Mahus (MtF) Polynesia; one per village; F dress; scared dance HIjras (MtF) India/pakistan; cut genitals; work religious dancers; prostitutes for Ms; kathoey (MtF) Thailand; genital reconstruction surgery; entertainment field Amazons (FtM) NE Brazil; warriors in M garb; M social role trans M (FtM) trans F (MtF) usually attracted to opposite sex/are heterosexual w/ respect to gender identity nonclassical trans F: autogynephilia; little sign of gender non-conformism in childhood; attracted to Fs; heterosexual w respect to sex assigned at birth; marry Fs & father children; fetishistic elements (paraphilia) = erotically aronsed by wearing F clothes; ideation to be in a F’s body & possess vgina; desire to become a woman fueled by desire to incorporate objects of their attraction (F) into themselves, rather than by an innate F gender identit; argument against autogynephilia: conflates paraphilia w/ trans; pathologies; reduces F to sexual behaviors/motivations; tbh just late onset dysphoria; more appropriate. is F embodiment fantasy which de-couples sexual behavior w/ gender identity, avoids needless mischaracterization & stigmatization of transF biological correlates: twin study: XY M MZ twins 33.3%; XX MZ twins 22.8%; XY/XX DZ twins 2.6% –> suggests genetic influence; dysphoria appears heritable; genes:CYP17: enzyme for prod. steroids; high levels of est. prog. & T may influence dev. of M gender identity during dev; AR (androgen receptor) = variation in transmit; other estrogen receptor genes also implicated; BNSTc: 2x larger/# neurons in XY than XX; trans F = F size; trans M = M size (no orientation correlation); INAH3: trans F = F typical size; trans M = M typical size; white matter: thinner in XY than XX; M-shifted patterns in transmit (midway b/w M & F patterns) COAEs: XY children w/ dysphoria = F COAES; XX children w/ dysphoria = F COAEs –> evidence for XY children w/ dysphoria may have exposure to lower amounts of androgens; Transitioning: psych/physical eval; real life exp for 1-2 years; hormones; gender affirming surgery (age at surgery affects outcomes –> postpone puberty in younger people w/ dysphoria w/ goal of improving surgery; ENDA: attempt to include protections against discrimination for trans- failed 2007; 21 state prohibit discrimination based on gender identity in employment housing, & public accommodations; 2015: equality act: prohibit disc. based on orientation & gender identity (fate uncertain); 2013-16: bathroom bills (24 states) –> restrict bathroom use by trans ppl; passed in NC, got repealed; 2017 ban on military, reversed 2021; 2018: define gender as bio. at birth (genitalia); intersex affected) leaked; did not proceed backlash; Bostock v. Clayton = Civil rights act protects employees from discrimination based on sexual orientation & GI; 2021: SAFE – see adolescent s from experimentation (Arkansas) = felony for dr.’s to do surgery or give blockers to trans youth, later, in Texas, prison time or loss of custody for parents giving gender affirming treatment for trans children; passed & is law