AN263 Exam 2

Male Reproductive Ecology

T levels not improved by increased nutritional status

Resource Competition

as a species, humans compete less; resource competition is extreme in humans - especially in stratified societies where the means of production can be controlled

Testosterone and Aggression

differences in testosterone don't tell us about individual differences in levels of aggression; individuals with more T not more aggressive; aggressive behavior can lead to increased T, not the other way around (T doesn't increase violence until quadrupled)

View of Female Sexuality

during Victorian era, female sexual desires were thought by many to be abnormal

Reproductive Success in Women Limited by:

energetic constraints on reproduction, ability to find and retain a mate, and offspring survival

In Men:

energetic constraints on reproduction, ability to find and retain a mate, offspring survival; human males can exert much more control over females and female sexuality than is seen in most other mammals

Hazda of Tanzania

fathers played more with biological children; male care was not just mating effort; fertile women = less investment (men will mate more and invest less); biological children received more care than stepchildren; provide less care as mating opportunities increase

Adaptive Hypothesis: Intermittent Reinforcement

female orgasm has been selected to be irregular - increases likelihood of mating; encourages extra-pair copulations (EPC) - little evidence that human females engaged in closely spaced repeated copulations with multiple males - non-human primates have orgasms, but not during intercourse

Female Orgasm as Non-Adaptive

females have low variance in reproductive success (RS); variance in sexual behavior does not affect a woman's RS (asserts that women who are more sexual don't have more kids; no direct evidence for or against this assertion); female orgasm is a by-product of mammalian bi-sexual potential; orgasm is possible because it is adaptive for males; can't be adaptive because it doesn't always happen

Is the Clitoris a Product of Natural Selection?

function: transmits pleasure upon stimulation that may or may not culminate in orgasm; size and position of clitoris shows variation between primate species, implies it has been under selection; structure has evolved for purpose of transmitting sexual pleasure to women; in humans, clitoris is sometimes removed as a way to remove/control female pleasure

Sperm Count and Overtraining

goes down with age; energetically stressed men have better sperm count

Sexual Behavior Adapted to Conception

gorillas: 20 copulations per baby

Hormonal Changes in Father

highest prolactin and cortisol in late-prenatal group; higher T led to higher mating/fathering success...but overall fathers had lower T than non-fathers; men who had children <1 year showed larger drop in T levels; men with 1-3 hours spent in childcare per day had lower T than those reporting no childcare

Non-Conception Sex

homosexual behavior (birds, mammals); non-conceptive hetero behavior (infertile) (many pair-bonded birds); some animals sexually diverse; male-male copulation by grey whales, botos, manatees

Offspring Survival

human males can invest more in offspring survival (direct care and resources) than in most other mammals

Testosterone and Fathering

human males have huge range of investment (sperm donor <--> single dad

Primate Sexuality

non-reproductive sex is not uniquely human

Testosterone

not a male hormone; loaded; fluctuates throughout the day

Resolution

return to pre-orgasmic state

Orgasm in Female Primates

rhesus macaques; stumptail macaques; Japanese macaques; orangutans; chimpanzees; bonobos *All involved manual stimulation, not during intercourse*

3 Classic Misconceptions of Sex:

sexual behavior that does not lead to reproduction is unnatural and therefore: wrong, evidence of mental illness, irrelevant to biology

Problems with Non-Adaptive Hypothesis

"variance in sexual behavior does not affect a woman's RS" assumes that females in a natural state ~unlike males~ breed at or near their reproductive capacity and that there is little room for natural selection to operate on females; assumes that copulation serves no function other than insemination; assumes females can't improve their RS by mating with multiple males

Evidence of Patriarchy in Historical Record

-3000+ years ago: humans became more patrilocal -after agriculture: increased need for male alliance formation and male control over resources needed to survive and reproduce; increased variance in male wealth and power, leading to increased male dominance *some women may also gain from patriarchy and help perpetuate it

Why do Humans have Concealed Ovulation?

-Morris '67: continuous receptivity in humans, strengthens pair-bonds and increased paternal investment in offspring through frequent copulations; CRITICISM: evidence of high, non-reproductive sexual behavior in non-pair bonding primates; low rate of sexual activity in other pair-bonded -Alexander Noonan: not about mating frequency but concealed ovulation; forces desirable males into consort relationships long enough to ensure paternity/not seek other matings -prevention of women themselves limiting the # of their children because of the pain of childbirth; CRITICISM: no modern evidence of this, it might have evolved before the increase in brain size and this painful childbirth -humans don't need it it in out type of social system; humans pair-bonded and females don't want to solicit matings from all community males; takes energy, which we don't want to waste

Female-Female Competition in Gorillas

-all females mated during pregnancy -all females mated more than expected on days when other females mated -matings of one pregnant female stopped when no other females were mating -WHY? to reduce sperm available to other females; to elicit male support; to increase female rank; to receive protection from harassment

Division of Labor

-all human societies have a sexual division of labor: men responsible for more high risk items (hunting large animals); women responsible for most of staple diet (gathered foods, shellfish, small animals) -age division: children and older adults contribute and have specific tasks -skill division: increasingly important with complex, technological society, can supersede sexual division of labor in modern society

Male Hormonal Functioning

-as testosterone falls, hypothalamus stimulates anterior pituitary to produce FSH and LH -FSH promotes spermatogenesis -LH promotes production of testosterone in interstitial cells

Changes with Circumcision

-cornification of the glans - increased thickness (10x) in outer cell layer; free nerve endings disappear; surface cells covered with a layer of dead cells -smegma no longer produced for lubrication -skin on penile shaft is tighter (because sutured at one end)

Degree of Sexual Division Varies

-depends on a number of factors including subsistence base

Is Female Sexual Pleasure Adaptive?

-does the potential for female sexual pleasure affect her behavior and her reproductive success? increase the probability of seeking extra-pair copulations, which under some circumstances may lead to: improved "genetic" quality of offspring; paternity confusion and investment from 1+ male ; strengthen the duration of pair-bond with investing male - influencing offspring survival -does arousability increase probability of conception? arousability facilitates copulation; intercourse alone causes release of oxytocin - may increase sperm uptake (directs sperm toward dominant follicle); maybe not about conception at all but just selection for female pleasure -does female sexual pleasure play a role in female mate choice? (ex: result of sexual selection?) but how much does female sexual pleasure derive from "male technique"? females may experience more pleasure from males they are interested in; is it really more about the female herself than her partner? sexual pleasure can evolve for non-reproductive purposes (ex: bonobos)

Human Foragers

-during poor food periods, men converge on women's strategies -see less division in poorer environments

China

-foot binding: 3rd century; emperor said small feet = beauty; formally banned in 20th century; restricted movement; upper class couldn't walk far; denotes upper class status (didn't need to rely on feet); done as a young child, before arch development; mother usually did it, fall/winter (numb); soaked in warm water or animal blood and herbs, nails clipped, foot massage; four small toes broken and bent down, tied, and pulled together; continuous process, smelled bad, as broken toes would die due to no blood supply; puss; 5-6 years; degree depended on status; deep cleft thought to be very erotic -high heels = manifestation of this today (emulates pregnancy, which shows fertility)

Testes

-gamete and hormonal production: leydig cells - manufacture testosterone; sertoli cells - support and nourish sperm cells -seminiferous tubules: sperm production -epididymis: sperm storage; become spermatoze (2-4 days); develop swimming ability -vas deferens: brings sperm to urethra -spermatic cord

Why do Women Gather?

-gathering = primary human foraging adaptation; women limited by access to resources and take the most dependable strategy so they can feed themselves and their dependents; more compatible with childcare (often DO hunt small game)

Sperm

-head contains chromosomes -acrosome (covering the head) -> enzymes dissolve egg membrane -middle piece - mitochondria -tail - contains microtubules (cilia and flagella) *ONLY cell whose function is to do something in someone else's body

Evolution of Patriarchy

-if males and females shared a means of production, relationships were probably fairly egalitarian, as they are with modern foragers -for most of human history, females probably had substantial control over their production and reproduction -likely varied with degree of reliance on hunting -Neolithic Transition led to agriculture and land became more valuable (male-male coalitions to protect land; patrilocal residence pattern, increased male-male alliances; increased male control of resources that females need to survive and reproduce) -agriculture leads to surplus goods and accumulation of wealth - land and resources can be passed on between generations THUS increased importance of paternity certainty via the control of female sexuality

Pre-requisites for Sexual Division?

-if one sex engages in risky foraging strategy must be able to have something to quickly eat if not successful; need to eat food that doesn't take all day to gather; cooked food would have enabled this

Female Genital Excision

-increased HIV/AIDS; 137 million women (1998); 2 million girls/year; primarily practiced in Indonesia, Middle East, and Sub-Saharan Africa -Northern Sudan: outlawed in 1945 but it has been increasingly prevalent -4-10 years old; older women keep the tradition going - safeguards virginity, thus protecting the honor of woman's and husband's patrilineage (guarantees paternity certainty to husband's family) -paternity certainty especially important in patrilineal, patrilocal, and patriarchical societies -needed because of "threat of female sexuality" (seen as protecting women from adultery/social condemnation) -98% have had this done; many complications - 38% have immediate, substantial complications

Sperm Maturation

-inside germinal epithelium of seminiferous tubules; -sperm cells develop from spermatogonia embedded in germinal epithelium (wall) of seminiferous tubules (nurtured by sertoli cells) -repeated mitotic divisions produce more spermatogonia; spermatogonia mature into primary spermatocytes: -primary spermatocytes undergo meiosis (chromosome # halved) and become secondary spermatocytes; -further mature into spermatids before ready to be released into lumen (liquid center) of seminiferous tubules (74 days)

Purdah

-institution related to control of women's sexuality and perseverance of family honor in Arab Muslim societies of Near East (most extreme in upper classes); female modesty represents honor of family (females competing for high status males; one patrilineage guarantees paternity certainty to another) -claustration maintained by men and husband's female kin -Paternity certainty guaranteed by: seclusion; veiling in public, child betrothal, virginity tests (hymen breaking, though it does so naturally for most women, showing bloody sheets, sometimes genital excision) -benefits to male of good marriage for daughter: alliance with high status kin group; exchange for bride; resolve feud by giving her in marriage; bride-price

Why did Purdah Develop in Middle East/Arab Peninsula?

-more you depend on pastoralism, the more patrilineal...why pastoralism (herding) associated with patrilinealism? wealth tied up in animals = can move, raid and steal others' wealth, so want strong male alliances; herd animals easily stolen, so the effective defense of livestock is critical -> development of powerful kin groups; male status important, revenge, culture of honor -wealth inequalities, frequent polygyny, violence all contribute to the control of women

Are Bonobos the Most Sexually Active Primates?

-mothers mate 3 years in between births; g.g. rubbing, masturbation, both sexes, "play sex" as juveniles -REASONS: reconciliation, tension regulation, expression of social status, social bonding.alliance formation -(more clitoral stimulation in bonobos with g.g. rubbing (more toward front)) -correlated with T levels across all cycle phases -higher baseline level of T in bonobo females may promote more g.g. rubbing -sexuality can be situation dependent

Bofi: Northern Congo

-net hunters, crossbows, spears, small traps, snares; men, women, children all have different roles; both genders gather in the forest but women do most of daily gathering

Aka Pygmies

-net hunters; low division of labor compared to other groups; fathers 2nd most active care group behind mothers (intimate, affectionate) -paternal care more common if father: doesn't have brothers, wife is from distant clan (needs him more b/c she's far from kin); married late; monogamous; not high status; men with fewer resources spend more time in direct child care

Control of Female Sexuality

-paternity certainty -societies with extreme control of female sexuality: develop with stratification of society after development of agriculture; accumulate resources can be passed on to male heirs, thus there is increased importance of paternity certainty

Benefits of Non-Religious Circumcision

-possible slight decrease in sensation -possible slight decrease in rates of penile cancer and STDs -1% risk of urinary tract infection during first year of life without circumcision -decreases AIDS risk

Functions of Foreskin

-protects glans of penis - shield glans and urinary opening from irritation due to feces and urine (newborn) and friction -smegma - produced by Tyson's glands of glans (protects glans; lubricates glans during intercourse

Medeval and Renaissance Europe

-rarely left homes -immoral to talk to men -married off strategically (chosen by father and brothers) -dowry = things that come with bride to groom's family -chastity belts: end of 14th century, popular during Crusades (sometimes husbands would die at war and these iron belts would stay on); messy, poor hygiene; 1933, Hungary: keys kept by fathers; used in modern Indonesia, Jakarta

Why is Control in Female Sexuality Greater in Some Societies?

-religion plays a role --> codifies restrictions and controls on women; increase in female, freedom with more secularization of society -polygyny = increased competition between males for mates (large number of men without wives means the need to sequester women; more wives = harder to monitor)

Clitoridectomy/Infibulation

-removal of clitoris and all/part of the labia majoria, mons veneris, labia minora; surgical closure of vaginal opening I: clitoridectomy, clitoris excised II: clitoridectomy with partial III: infibulation , clitoris excised, labia minora excised, majora fused -deinfibulation: cutting open scar tissue for intercourse/childbirth -reinfibulation: fusing again after childbirth

Costs of Non-Religious Circumcision

-risk of non-essential surgical procedure mutilation damage 1-3% -emotional stress on baby -ulcerations formed around urinary opening -decreased glans sensitivity -lack of production for lubrication -increased tightening of skin/shaft

Why Circumcision?

-ritual circumcision found especially in strongly patrilineal/patriarchal societies; symbolizes belonging to a male kin group and/or religious affiliation (why the penis? real investment and trusting it'll go right) -non-religious circumcision developed in English speaking countries at end of 19th century as a "cure" for masturbation -US = only country in world with routine non-religious circumcision (80+% men in world not circumcised)

Seminal Fluid

-seminal vesicles: base of bladder -prostate gland: just below bladder -Cowper's gland: either side of urethra -contains sugars and prostaglandins that cause uterus to contract

Why Don't Men Gather Too?

-they do in times of food stress, but they bring rare food back when they can -hunting is unpredictable, but these high value items provide caloric boost and needed vitamins (B12) -sexual division of labor leads to structure of pair-bonded males and females living within a multi-male multi-female social structure

How Societies Control Females and Their Sexuality

-two standards of sexual behavior for men and women -divorce difficult for women (female cheating = ground for divorce, but not male) -parental choice of mating partners -early age of marriage -live with groom's family (matrilineal) -ownership of women -veiling and other clothing -violence and threat of violence for breaking taboos -restricted access to males -claustration/seclusion -females and their families compete for access to high status males through the purity of their women -more extreme with higher social status

CONCLUSIONS Regarding Paternal Investment

-where resources are not accumulable, men spend more time in direct care of children -where resources are primary contributors to subsistence, fathers invest more time in competing for resources and thus spend less time in direct child care

Chimp Sexuality

6 seconds; estrus swelling to advertise ovulation (and attract males); try to mate with all males in community; 30-40 times/day; concentration of mating with dominant males mid-cycle

Multiple Orgasms: Women?

14% of women; return to the plateau phase, rather than resolution

How do Women Achieve Orgasm?

95% easily with masturbation; women masturbate through manual stimulation of the clitoris; 1.5% through vaginal insertion alone; little cross-cultural information

Spermatogonia -> Primary Spermatocytes -> Secondary Spermatocytes -> Spermatids -> Spermatozoa

Germ Cells -> Mitosis -> Meiosis -> Further Maturation -> Mature Sperm

Terseus

Greek mythological character who was both man and woman (killed mating snakes and Hera changed him); said women experienced 9x the pleasure of men

Does Paternity Confidence Affect Investment?

[survey in Heathrow airport] 1) phenotypic resemblance to child 2) perception of mate's fidelity (invested more in these cases)

Mate Value

asked men how they perceived themselves: positively related to mating effort and negatively related to reported paternal investment; men with lower perceived self mate-value more likely to put up with infidelity and lowered paternity

Problem with Debate

assumes female orgasm = female sexuality

Male Puberty Rituals

bar mitzvah; subincision of the penis (Australian Aborigines); penile modification (Dyaks of Borneo); Circumcision (most common modification) COMMON: -modification of penis (shedding of blood) -changes in clothing -changes in hairstyle -inducement of trance state

Evolution of Human Penis Size and Shape

bipedalism - response to changes in female reproductive tract? long copulations? increased female stimulation? display?

Is Female Orgasm Adaptive?

capacity may be universal, although not universally realized but not necessarily from intercourse; higher sperm retention when female orgasm occurred around the time of ejaculation

Ache of Paraguay

children of good hunters have higher survival rate; group decision making may be biased toward good hunters

Practice Sexual Behavior by Juveniles

chimps: barely weaned males (2 years) practice with females, including mothers; baboons: juvenile males mount females)

Testosterone and Behavior

close relationship in chimps, but not as close in humans

Male Reproductive Strategies

control of females/female sexuality; male-male competition (investment in offspring and mating effort)

What Made Sexual Division of Labor Possible?

cooking - made hunting possible because it provides time

Vasectomy

cutting of vas deferens; sperm don't come out; can be reversed sometimes

Cultures of Honor

importance of reputations; herd animals valuable and easily stolen; American South??

Function of Estrus Swelling

incite male-male competition; sperm competition; ensure mating with dominant males; advertise fecundity; helps immigrating to a new community

Sexual Response Cycle (same steps for men and women)

like penis, clitoris fills with blood from sexual arousal; crura of clitoris under labia minora, invested with muscles; only function of clitoris is sexual arousal

When Did Sexual Division of Labor Come About?

likely evolved AFTER or with evolution of homo erectus (1.8mya); at this time, we see significant changes in body showing higher diet quality: cooking; 1st substantial evidence of meat eating in fossil record (likelt changes in human life history)

Orangutan Sexual Diversity

male-female: genital fondling, fellatio, licking of female genitals; young adult and adolescent males: genital fondling, fellatio, anal intercourse (pelvic thrusting and ejaculation); female-female: genital fondling, g.g. rubbing

Reproductive Strategies

males and females have different reproductive interests and constraints

Gorilla Sexuality

mating confined to a few days around ovulation; slight sexual swelling in nulliparous females; females solicit mating from silverback males

Hormonal Emancipation in Old World Monkeys, Apes, and Humans

more female sexual "control" of mating; more female initiation; more sexual coercion because males don't know when females are ovulating and mating could occur at any time (vagina open all of the time, which is not the case for some animals, so they CAN'T mate all of the time)

Penis Complexity and Mating System

most complex morphology where sexual selection most intense - where females mate with 1+ mate; penile complexity associated with multi-male mating systems

Investment

necessary for offspring survival; paternity certainty is high; access to mates is socially limited; resources can be passed on; when there's more investment in offspring when more (female) control; monopolize females by controlling sexual access to them on a short term

Multiple Orgasms: Men?

pattern seen in pre-pubescent boys (55%); 8-15% of younger adult males and 3% of adult men; ejaculation seems to prevent return to plateau stage

Baculum

penis bone (facilitates retraction of penis; associated with longer periods of intromission; humans don't have one)

Women Judged to be More Attractive when Ovulating?

perhaps...higher preference in "unmasked" but still detected fertile phase even in masked condition

What is Out Sexual Inheritance?

primate females are more actively sexual than previously thought; primates engage in sex for other reasons than procreation; some evidence for orgasm in female primates through manual stimulation

Plateau

prominent vasocongestoin in outer 2/3 of vagina cause tissue to swell - vagina narrows by 30% or more - clitoris pulled back against pubic bone (covers/protects from direct touch) - labia minora may double/triple in size - color changes develop

Orgasm and Oxytocin Release

release of oxytocin during orgasm (may increase sperm uptake); oxytocin directs sperm toward dominant follicle

Circumcision

removal of foreskin

What is sex for?

reproduction, pleasure, bonding, resolving conflict

Hormones and Sexual Behavior

some evidence of mid-cycle peak in female sexuality; no consistent mid-cycle rise in sexual activity (in pairs, alone, or lesbians); slight rise in T around time of ovulation (increase in coital frequency during ovulatory period remains a possibility for humans but hasn't been convincingly demonstrated

Testosterone

sperm maturation; stimulates growth and development of penis and testes; male secondary sexual characteristics (axillary hair, larynx, oil and sweat gland secretion); may need threshold for sexual activity and libido; T can augment pre-existing pattern of aggression; key promoter of muscle anabolism; increases muscle mass, especially when combined with exercise

Sperm's Journey

spermatids released into lumen of seminiferous tubules; move through tubules and water is replaced by fluid from seminal vesicles and prostate; stored in epididymis

Orgasm

through intercourse alone: indirectly from penile shaft distention (manual traction) of labia minora at opening of vagina or through manual stimulation; contractions at 8 second intervals; average time = 4 minutes (masturbation for men and women) and 10 minutes (intercourse for women)

Penis

urethra carries urine and semen - NOT at the same time; mechanism makes sure there's not a mixture

Excitation

vaginal lubrication: transudation - vasocongestion in walls of vagina lead to moisture - inner 2/3 of vagina expands - cervix and uterus pulled upwards - labia majora flatten and move apart - labia minora and clitoris enlarge - contraction of small muscle fibers in nipples - breast size may increase - veins on breast more visible

Male Investment

when should males invest in spouses and/or children instead of seeking more mating opportunities?; necessary for offspring survival

Triver's Hypothesis (1972)

whichever sex invests more effort and resources into offspring is, in effect, the limiting resource for the reproduction of the less investing sex and thus the object of competition

Risk-Taking

women NOT on the Pill less likely to do something risky when ovulating