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Sex and Reproduction > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

Sexual Behavior

A 
Gender Traits
Libido
Sexual Orientation
Gender Identity
Attraction/Mate Selection
Mate Bonding
Monogamy vs Polygamy
Receptivity
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2
Q

Behavioral Traits are Extremely Diverse Across the Human Population

A

They are the result of interactions among a suite of factors that include biology, experience, and context.
GRAPH

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3
Q

Gender TraitsMasculine vs Feminine

A

Nature hypothesis
The exposure of the non-sexual brain to steroid hormones at a Critical Period during gestation & perhaps following birth, organizes into masculine or feminine variants, specific regions of the brain responsible for sexual behavior.
Nurture hypothesis
Humans are taught, implicitly and explicitly, to behave in a manner appropriate to their biological sex.

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4
Q

Gender Traits

A

It is currently accepted that the ‘either nature or nurture’ dichotomy is false.

In actuality,
both steroid hormones and socialization interact to determine and modify gender traits
masculine and feminine traits are not always associated or correlated with biological anatomy

Bottom Line: In any individual, biology and culture interplay to give rise to gender traits.

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5
Q

Libido: conscious or unconscious sexual desire

A

Male sexual drive:
androgens within a defined range are necessary but not sufficient (androgen levels required are below that necessary to maintain spermatogenesis)
evidence suggests that certain brain traits that are androgen-independent are required
Female sexual drive:
no ovarian hormones are correlated to sexual drive but tonic levels of androgens may be needed
‘psycho-social factors’ may dominate any hormonal influence, particularly in younger females

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6
Q

Testosterone Production by Age in Males & Females

A

GRAPH

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7
Q

Puberty & First Arousal

A

GRAPH(2)

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8
Q

Sexual Orientation

A

Heterosexuality or Gender Typical Partner Choice: choosing to sexually interact with partners of the opposite sex

Homosexuality or Gender Atypical Partner Choice: choosing to sexually interact with partners of the same sex

Question that often arises: Does it have a biological basis?

Finding a biological basis has been difficult and may be due to limited scientific studies in this area. Also, there are probably multiple biologic factors involved.

Many ask: Why is it important to find a biological basis?

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9
Q

Sexual OrientationEvidence for Biological Basis

A

Hormone Comparisons
No differences have been found in hormone levels between heterosexuals and homosexuals.
Brain Anatomy
Studies claiming to find brain differences in women and homosexual men when compared to heterosexual men have been debunked. A causal correlation between brain anatomy/function and homosexuality has not been unequivocally demonstrated.

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10
Q

Sexual OrientationEvidence for Biological Basis cont.

A

Genetic Differences

Two Studies

1993 (Hamer): found DNA ‘markers’ on the X-chromosomes (Xq28) of homosexual brothers (40 pairs).

2014 (Sanders): found DNA ‘markers’ on the X-chromosome (Xq28) and chromosome 8 (8q12) of homosexual brothers (409 pairs).

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11
Q

Behavioral and Molecular Genetics

A

Family and Twin Studies

Homosexuality is increased among relatives of homosexuals

Elevated maternal line inheritance (homosexual maternal uncles)

Both suggest chromosomal – autosomal- or X-Chromosome-linked, respectively

Twin Studies – If one twin is homosexual, what is the probability that the other (same sex) will be?
GRAPH

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12
Q

Fraternal Birth Order EffectFBO

A

For males, number of older brothers (gay or not) increases chances of being homosexual by 33% for each older brother

Estimated that 1:7 homosexual males may be due to FBO

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13
Q

Epigenetic Effect Hypothesis

to explain homosexuals in families with no genetic effect identified…

A

EPIGENETICS: chemical signals on DNA that control which genes are read and how much

These chemical signals are inherited from parents

PROPOSE epigenetic effect acting on how cells respond to androgen signaling in the brain: steering opposite effects in males and females, i.e. driving each toward opposite brain effects
PROBLEM:unreliable data so far

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14
Q

Gender Identity: the sense of being male or female

A

No physiological parameters of gender identity have been identified.

Studies depend on what people say about themselves.

Is gender a discrete property with just two possibilities (male or female) or is there a continuum of gender identities?

Does gender occur at multiple biological, anatomical, physiological and psychological levels?

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15
Q

Sexual AttractionMate Selection

A

Attraction between males and females is culturally influenced and dependent upon

visual cues
auditory cues
olfactory cues
other chemical cues

The first two are most often studied in a psychological context, but the third intrigues biologists.

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16
Q

Pheromones

A

chemical compounds released by one individual that elicit a physiological response in another individual

Human sensory systems
Sources of human pheromones
Roles of pheromones

17
Q

Human Sensory Systems

A

Main Olfactory System (MOS)
olfactory receptors in the nasal cavity detect odorous compounds
signals are sent to higher brain centers so perception is conscious
Accessory Olfactory System (AOS)
receptors in the floor of the nasal region detect compounds that may have no odor (vomeronasal organ or VNO)
signals are sent directly to hypothalamus, bypassing higher brain centers, so no cognitive perception

18
Q

Probable Source of Human Pheromones

A

Apocrine Glands
mature at puberty
secrete odorless substance
bipedal human stance may accentuate the distribution of substances

19
Q

Possible and Putative Effects of Pheromones

A

Sexual attraction between males and females.
Control of female monthly cycles.
presence of males
Infant-mother bond in early postnatal period.

20
Q

Sexual Attraction/Mate SelectionOther Chemical CuesMajor Histocompatibility Complex (MHC)

A

The MHC is a multigene family that codes for key receptor molecules that recognize and bind foreign proteins for presentation to specialized immune cells which initiate an immune response.

Humans have been shown (when not distracted by artificial odors) to choose partners with a high degree of variability from their own MHC, thus insuring immune systems in offspring with wider capabilities of recognizing foreign substances.

21
Q

Stages of Mate Bonding

A

Lust – novelty of early attraction and sexual interaction stimulates dopamine release, which acts as a natural opiate, increasing feelings of intense energy, exhilaration, focused attention and motivation. Low serotonin (similar to depressive conditions) promotes ‘obsessive’ love.

Romantic Love – increased tolerance of dopamine reduces the initial ‘drugged’ feeling, but feelings of long term bonding and closeness are supported by oxytocin.  Oxytocin levels are maintained by
making love
orgasms with your partner
hugging your partner
massaging each other

Attachment – long term maintenance by high levels of oxytocin.

22
Q

Monogamy vs Polygamy

Polyandry vs Polygyny

A 
Polygyny = males have more than one female mate
Polyandry = females have more than one male mate
23
Q

Our Clostest relatives

A

Our closest relatives are the Chimpanzees and the Bonobos (pygmy chimps)

We share from 98 to 99% of our genes with them.

BUT, which genes do we share??

24
Q

Info about Chimpanzees

A

In Chimpanzees ♂♂ are dominant and choose with whom they will mate. One ♂ is dominant & fights off other ♂ ♂ of the community to keep ♀ ♀ to himself.

When ♀ ♀ reach maturity, they leave to find another community.

Disputes over food, mates, territory, etc. are settled by aggression and fighting.
Sometimes, community members leave their territory to attack other communities.

25
Q

Bonobos

A

Bonobos have sexual activity with ALL members of the community.
males with females
males with males
females with females
adults with young (all combinations)
Disputes over food, mates, territory, etc. are settled by sexual activity!
♀ ♀ are dominant in communities and choose with whom they will mate. When ♂♂ reach maturity, they leave to find another community.

26
Q

Problems with publications about Bonobos

A

nearly all data were collected in captive populations
is the activity observed between adults and young, same-sex individuals, etc. really sexual activity?

BUT! Recent comparison between chimp and human Y-chromosome indicates that:

Most genetic differences between humans and chimpanzees occur on the Y-chromosome!!

The chimpanzee Y has 50% the number of genes as the human Y.

SRY – sex determination
Gonad formation
Sperm production
Etc.

27
Q

Receptivity in the Female

Continuous vs Estrus

A

We are the only primate whose females have hidden estrus (cycles).
Human women do not show when they are fertile, and in fact, often do not know themselves when they are fertile.
Consequently, human females are (usually) receptive to sex at any time.
Does this keep males closer to home?

Sex and Reproduction (7 decks)

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