Exam 2: Week 9 Flashcards
T/F same sex people produce fewer offspring?
True
- Seems to be a costly trait from perspective of natural selection
- The trait is common and possibly increasing in frequency
- likely a cultural evolution rather than genetic but rates of reporting are what may be increasing instead of homosexuality itself
- Gay American men have 10-20% as many children as straight men
what are the population estimates for same sex %?
10%
- other studies have 2.8% of men and 1.4% of women
what is the Kinsey scale?
sex (gonads, genitalia) is mostly binary but sexual preferences appears to be more of a continuum
sexual orientation
same sex behavior in animals/humans ⇒ learning who to love via social and environmental impacts as well as genes
what are the evolutionary explanations for sexual orientation? (3)
- Kin selection
- Alliance formation
- Antagonistic pleiotropy
T/F in most species studied at some point we see same sex mounting behavior?
True
- not as common as heterosexual behavior
- Often occurring in the context of social relationship ⇒ already in close relationships or are building relationships
philopatry
the pattern in terms of which sex stay in the group they are born ⇒ someone must disperse in order to avoid inbreeding and inbreeding depression
- This pattern is the same in chimps and bonobos ⇒ typically male philopatry where males stay in the group they are born
how would philopatry affect female relationships?
Females have to go out and make new relationships
- For species where each sex disperses, one sex will disperse further to avoid inbreeding
imprinting
a type of learning different from association learning and instead is stereotyped where the first moving thing a baby sees it will fixate on to learn species appropriate behavior ⇒ typically found in birds
- Usually is a parent in the wild but could be anyone
prococial
babies that can do a lot of things on their own when born ⇒ humans are the complete opposite
how do geese learn appropriate sexual partners?
newly hatched geese exposed to a moving object of reasonable size and emitting reasonable sounds will begin to follow it just as they would normally follow their mother
- A gosling imprinted to a moving box or clucking person will try to follow this object for the rest of its life
- When the goslings reaches sexual maturity, it will make the imprinted object the goal of its sexual drive ⇒ rather than a ember of its own species
how do whooping cranes breed?
by dancing with appropriate partner
- Cranes imprinted on people must dance with people to breed
- Because of risks of imprinting, captive condors must be fed by puppets
what happens with baby monkeys and maternal care?
baby monkeys need love
- The wire mother had food while the cloth did not but infants showed persistence preference for the cloth mother over the food mother
- When hungry they wouldn’t leave the cloth mother ⇒ they would lean over to nurse but still touch the cloth mother (attachment bond from infant)
what happens to monkeys raised by cloth or wire mothers?
they have insufficient social contact and develop poor social skills
- Isolated infants became bad mothers
- shows appropriate sexual behavior depends on childhood social interactions, not just physical maturation
how do human children develop models of appropriate sexual partners?
from their parents
paraphilias (6)
learned associations between sexual response and unusual stimuli => more common in men
- exhibitionism
- fetishism
- frotteurism
- pedophilia
- sexual masochism and sadism
- voyeurism
exhibitionism
wanting to be seen naked
fetishism
unusual behaviors during sexual behavior
frotteurism
engaging in unwanted rubbing of genitals against another person
pedophilia
engaging in sexual behavior/fantasy with prepubescent individuals
sexual masochism and sadism
arousal from pain
voyeurism
watching sexual behavior of other individuals
cases where same sex behaviors that may depend on segregation? (3)
- prisons
- schools
- military
T/F different cultures have different definitions of friendship and homosexuality behaviors?
True
what do twin studies show us about homosexuality?
in identical twins, if one twin was gay, the other had 50% chance of also being gay
- For fraternal twins, the rate was about 20%
- Controlled for social settings and exposure to biological parents
- there is a genetic element to same sex preference but not 100%
how are brothers affects by homosexuality?
Uterine development (mothers antibodies) against proteins from the Y chromosome
- The quantity of antibodies increases with each son a woman has which the fetus will swim in ⇒ maternal immune response to male fetuses
- This neutralizes the male Y chromosome which may impact their development and leaves some regions of the brain like the typical female arrangement
- Fraternal birth order effect: men with older brothers are more likely to be gay (33% increase for each son)
- 8-12% of brothers of gay men are also gay compared with the 2-4% of the general population
- gay brothers share a specific region of the X chromosome called Xq28 at a higher rate than gay men shared with their straight brothers but subsequent studied failed to replicate this
- there is a lo degree of heritability on same sex sexual behavior relative to other traits
what do clumps of neurons in the anterior hypothalamus tell us about homosexuality?
larger in heterosexual than homosexual men
what are differences in homosexual vs heterosexual sheep?
Examined a sexually dimorphic nucleus (oSDN) in the sheep preoptic area anterior hypothalamus
- The oSDN is larger in female oriented rams => Female sheep and gay male sheep have the same size of oSDN
- 8-10% domestic rams prefer to mate with other males
- Brain difference in sheep parallels brain difference identified earlier in humans
Kin selection (homosexuality)
Homosexuality may function like sterile castes in social insects ⇒ predicted homosexual men and women forgo their own reproduction but help their kin reproduce
- various studies have failed to support this hypothesis
male bonding
homosexual behavior leads to attainment of other resources
sparta
spartan boys were drilled under the eagles eye of their older lovers, the erastai, so as to become good warriors ⇒ only the eromenoi who married and raised children were allowed to become erastai themselves
alliance formation hypothesis
homosexual behavior promotes male bonding and serves as an honest signal of loyalty and trustworthiness ⇒ intrinsically linked with status
- High status males mate with more females than lower status male and have more offspring ⇒ low status males look for less confrontational strategies and may form alliances with other low status males to gain access to reproduction against dominant males
- Not just a binary in sexual behavior from people
domestication syndrome
homosexuality may be a byproduct of our species ⇒ humans are self domesticated
- Selection for particular behaviors causes changes in the physiology and behaviors of the organism
- Domestication favors traits such as docility that contrast to typical behavior of wild type males
do women tend to be lesbian or bisexual when they aren’t heterosexual?
Non heterosexual women tend to be bisexual rather than having exclusive same sex preference
- LUGs ⇒ lesbian until graduation refers to an experimental phase for young women in high school and college until choosing a partner later for marriage and producing offspring
- we don’t know much about lesbians
Antagonistic pleiotropy
one allele produces multiple, contrary effects ⇒ on morphology and behavior of an organism
- Some alleles may increase reproductive success in some contexts but reduce reproductive success in other contexts
what are advantages of having a brother who is gay for females? (3)
possibility that female kin on the mothers side have higher fitness and increased fertility but male kin on the fathers side do not (hierarchical society where women marry up and this Ould increase homosexuality traits in male kin)
- More sexual partners for heterozygotes
- Increased fertility/feminine attractiveness of sisters ⇒ of gay men who also carry allele
- Dedicated dads
Note: there is some evidence for this theory
Desirable dad hypothesis
heterosexual men who exhibit greater femininity may be more successful in mating, as measured by their greater number of opposite sex partners compared to other men
- some degree of femininity in men is a cue of paternal qualities
- Women who prefer paternal men have greater inclusive fitness than other women because raising human offspring to maturity requires significant time and effort
what is different about masculine appearing men compared to feminine?
- Men with more masculine facial features –larger jawbone, prominent brow ridge, wider cheekbones– tend to allocate more effort toward pursuing potential mates than investing in their offspring in comparison with men having less masculine facial features
- Men with masculine bodies had more sex partners and were more likely to cheat and mate poach
aggression (psychology)
behavior that is intended to cause harm or pain
- This is a human centered perspective but when discussing other species its not necessarily the same ⇒ meant to gain access to a resource
aganism
threats and intimidation where there is a meeting conveyed between individuals but maybe not physical ⇒ either the individual will leave or there is an escalation
- This is a bigger category than aggression
competition
individuals want a resource but there isn’t enough to go around so they compete/fight over it
contest
a moment in time when two individuals who are in a competitive interaction for a resource ⇒ may start with threats and intimidation and escalate to aggression
what is evidence for adaptation? (5)
- complexity, design features
- Directional change through a lineage
- convergence in design
- varies in a sensible way across biological space ⇒ regress where it is not important
- Has a cost
what are the brain structures that regulate aggression? Hormones?
amygdala, hypothalamus
- Serotonin is negatively correlated with aggression
- testosterone promotes male competitive ability (energetic cost)
what is the adaptation for canine teeth?
mainly weapons for fighting (not hunting)
- Tend to be larger in males
- Males spend a lot of energy and effort in conflict with other males for access to mates
what does dimorphism signal?
what happens in a particular species ⇒ if males have more pronounced features there was conflict for mating opportunities
what are bodily costs for female adaptations?
female primates investment in reproduction
- the cost is associated with menstrual cycle and growing the uterine wall for the egg and pregnancy, lactation, carrying the infant, caring for the offspring after weaning with social support, etc.
what are bodily costs for male adaptations?
fighting/injuries/energy expenditure, growth of body parts, creation of sperm
- When males are 80% larger than females they start to pay more in energy production than females do ⇒ effort and energy in fighting and body size
what are examples of costly traits (2)
- Weapons
- Larger body size
examples of complex design features?
Neuroendocrine systems
evolutionary patterns to watch for? (2)
- Directional change
- Convergence
is aggression a product of natural selection or pathology/aberration?
natural selectiona
aggression (evol. def)
a strategic response employed when assessment indicates the benefits are likely to outweigh the costs
what are the costs of aggression? (3)
- Risk of injury or death
- Time and energy that could be spent doing other things
- Investment in body size and weaponry
what are benefits of aggression? (4)
- Resources
- Mates
- Status
- Reproductive success ⇒ major benefit
why might organisms be aggressive? (2)
- Limited supply of goods needed for survival and reproduction
- Competition is universal => Aggression is just one of the possible strategies for competition
why don’t animals kill each other all the time if they have the capacity to do so?
There are outcomes decided on the basis of asymmetries in strength and motivation
- Best to use aggression as a strategic option
- The genetically selfish strategy is often to refrain from fighting unless the costs of fighting are likely to be low
what groups do fights occur more often with?
males and young people
what theories describe why males could be more aggressive than females? (2)
- social role theory
- sexual selection theory
social role theory
socialisation shapes gender specific identities, expectations, and behavior
Sexual selection theory
males are competing for reproductive success, so are more aggressive generally and especially to other males
is homicide an adaptation?
20-24 year old men are the most likely to commit homicide when unemployed
- people with the longest life expectancy show the lowest homicide rate in areas where they live
- the more income inequality the higher the homicide rate
- may be an adaptation in times of struggle
T/F females can also be aggressive?
True
end card
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