PSYC 385 Chapter Notes -Adaptationism, Cellular Respiration, Inclusive Fitness
9 Nov 2014
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Life histories
•adaptationist stance that assumes alleles producing life cycles we see in nature
have out-competed alternative alleles for longer, shorter or otherwise different life
cycles
olife cycles we see must be ones that make sense in terms of long term
reproductive success
•organism have finite resources → only capture energy from environment at certain
rate
oface problem of allocation → depend on current state, life
expectancy&offspring → depend ecology they operate in
lifespan
•Darwinian evolution produces organism that seek to preserve lives → one's repro
success is usually higher alive than dead
oaccount for great deal of motivated behavior
oparadoxical → no external cause of death → organism eventually die
reach age where multiple system of body begin to deteriorate until
fails completely
•senescence → multiple physiological processes deteriorate markedly
ogene reside in body at particular instant → body could die and gene endure
as long as body had reproduced
gene = immortal → body = disposable
ogain in reproductive success from living longer would not be enough to
offset cost in term of reduced energy allocated to reproduction earlier in life
odisposable soma theory → aging & death arise from accumulation of
unrepaired damaged to body cell
energy devoted to repair can slow this accumulation or abolish it
higher rate of extrinsic mortality → earlier senescence should occur
& more energy early in life should be devoted to reproduction
•extrinsic mortality → risk of prob of individual dying given time period through
events in envirothat could do nothing abt
ovary but never completely 0
•intrinsic mortality → mortality due to organism's own aging
•organism reproduce → allow gene to buffer themselves against extrinsic
oinvest some of individual's energy in making other bodies → alternative
genetic cargo
allele which caused its bearer to devote little more time & energy to
making copies of itself → higher fitness than others
allele which cause body to repair themselves more effectively →
higher fitness
organism with highest reproductive rate → allocate all energy
to reproduction and none to self repair
organism with best repair → allocate all energy to repair and
none to reproduction
tradeoff → doing more of one = doing less of other
reproduction
•greater mortality rate → greater extent to which higher reproductive rate should be
favored over long term maintenance of soma
ohigher extrinsic → more pays to live fast and die young
olow extrinsic → pays to invest for long term
organism with high mortality → show reproducing earlier, have more
offspring, devote more effort to reproduce
come at cost → higher mortality → smaller relative body
weight of offspring → less time can be gestate → sooner
mother stops nursing it
•body size → life history strategy
olarge → slower life history → takes longer → delays age of reproduction,
increase gestation → slows down reproductive output by metabolize less
energy → allocate relatively less energy to reproduce
•if ecological factor remain constant → tradeoff between energy allocated to growth
and reproduction
oincreased mortality rate tend to result in evolution of smaller size at maturity
and earlier reproduction
human life history
•slow → sexual maturity at 15 years old
•low extrinsic mortality
•achieve high reproductive rate give body size
•childhood period dependence is prolonged → reproduce cooperatively
okind and friends help provide resources for dependent offspring → allow
women faster reproductive rate
•tradeoff between continuing to grow and starting to reproduce
oex pygmy → small size → nutritionally stressed & live in high disease →
high rate of mortality
stopped growing sooner → reproduced earlier in life → adaptive
given ecology
i. genetic differentiation
•natural selection favoring different alleles for timing of growth and puberty
ii. phenotypic plasticity
•evolved capacity of phenotype to later its development in response to cues during
development that world is in one state or another
•all human evolved capacity to switch resources away from growth & into
reproduction if recieve cues in lifetime that mortality rate is high
•human evolved phenotypic plasticity to respond to harsh environmental conditions
by speeding up life histories
oex. when life expectancy is low → women have more babies & carry out
reproduction early
people respond to cues in their neighborhood & early life stress →
change life history strategy
