Lecture 3 Flashcards
What is epigenome
Set of chemical marks in an individual’s genome that affects in gene expression. This set of marks is heritable but can be modified by environmental exposures.
What are epigenetic factors
- non coding RNA
- histone modifications
- histone variants
- chromatin remodelling factors
- DNA methylation
Why is the epigenome necessary for development
- cell differentiation
- tissue differentiation
- life history events
What potential adaptive advantage could the epigenome provide
- allows for changes in expression of the otherwise static genome to respond to environmental conditions
epigenetic changes are associated with _____
environmental stressors
- changes are reversible
What is life history theory
- postulates that Ontogeny has been shaped by natural selection
- organisms are expected to follow resource allocation patterns across their lifespan that result in an optimization of their Overall Biological Fitness
What is ontogeny
development from the moment of conception
What is overall fitness
individual fitness + inclusive fitness
What is individual fitness
Offspring produced by self
What is inclusive fitness
positive? effect on the fitness of relatives
What is the formula to calculate trait would have positive selective value
- Hamilton
- rb> c
c - reproductive cost to self
b- reproductive benefit to recipient
r- coefficient of relatedness
How do individuals maximize fitness
by optimizing resource allocation throughout life span
What is the principle of allocation
at any given life stage resources used for one purpose cannot be used for another
How does natural selection relate to principle of allocation
ns expected to favour evolution of optimal allocation patterns
What do we need to allocate energy to
- growth
- maintenance
- reproduction
What are the human life stages
- prenatal
- childhood
- adolescence
- reproductive life
- post-reproductive life: menopause and andropause
What is senescence
- end of childbearing to death
Why are most nonsocial mammals weaned into independence while humans are dependent post weaning
- early human diet is particular… digestive system matures slowly but energetic demands are substantial
Why is human childhood particular
- relatively small body size
- comparatively slow and steady rate of growth
- dependent feeding
- Higher RMRs than any other mammalian species
- large expensive fast growing brain
- motor and cognitive immaturity
- adrenarche (shared with chimps) and mid-growth spurt (unique to humans)
What differentiates humans from apes
in humans delays in
- eruption of first permanent molar
- menarche
- first birth
- shorter birth intervals
- can rear multiple offspring simultaneously
What do short IBIs in humans provide
reproductive advantage over other apes because we can produce and rear 2 offspring through infancy in time it takes chimps or orangutans to produce and rear one offspring
Why can we rear multiple offspring simultaneously
other people can feed child -> reduction of period of lactation -> reduction of IBI -> greater life time fertility for mom
What explains human childhood
more time for developmental plasticity -> more precise tracking of socio-ecological conditions -> greater offspring survival rate -> greater life time fertility for offspring
What is special about human adolescence
- growth rate is quantitatively different in terms of amount, rate, and duration of growth
- length of time between age at puberty and age at first birth ~10
Why is the age of viable sperm - first child delayed?
- time to learn/practise hypothesis
- ecological risk aversion hypothesis
- proven value hypothesis
- resource accumulation hypothesis
What is the learning hypothesis
- brain growth and learning necessary for success
What is ecological risk aversion hypothesis
- avoid competing with adults for food and other resources - low profile until ready
why do girls experience adolescence
practise of parenting skills -> greater lifetime fertility
Female fecundity seems to track ____
the growth of the pelvis
What are two fundamental trade-offs in reproduction
- current vs future reproduction
- Quantity vs Quality
What is current vs future reproduction
- cost of reproduction
- reproduce now or later time?
- species/pop level, determines major demographic patterns
What is quantity vs quality
with the same effort: many cheap offspring or few expensive ones
- at species/pop level, determines life history traits such as duration of lactation….
What is Lack’s principle
optimal number of chicks: intermediate brood size lead to the highest number of surviving offspring
What was Blurton Jones’ study
- optimal IBI among !Kung IBI that led to the highest number of surviving offspring for them was also most common IBI in the population
____ and _____ has consequences for both moms and children
- timing
- intensity of reproduction
What are changes associated with senescence
- hormones
- immune system
- cardiovascular system
- body composition
- bones
- brain function
- reproductive system (menopause and andropause)
What are three hypotheses of menopause
- follicular depletion (proximate)
- timing of senescence (ultimate)
- grandmother hypothesis (ultimate)
What is timing os senescence hypothesis
end of reproduction set by a female’s age specific life expectancy and duration of infant dependency -> reproductive senescence occurs at appropriate age for investment in last offspring
What are discussions around timing of senescence hypothesis
- apes continue to reproduce
- humans may get kin to help raise offspring
What is grandmother hypothesis
- selection may have favoured early termination of childbearing in favour of investing in grown children and grandchildren
what are discussions around grandmother hypothesis
- isn’t it better to reproduce yourself than help relatives
- living with maternal kin is not universal
What are alternative hypotheses for menopause
- grandmother’s productivity
- patriarch hypothesis
- embodied capital (gender neutral)
What is grandmother productivity
led to selection for increased lifespan - efficient tuber diggers…
What is patriarch hypothesis
- shift to less strength based male male competition
- males can be high status and obtain mates even though not in ‘prime’ physically
- ability for males to keep reproducing selected for longevity
- selection on autosomal and passed to females
Problems with patriarch hypothesis
- sex biased
- when did less strength based skills evolve?
What is embodied capital hypothesis
- focus on co-evolution of brain capacity and longevity
- humans invest in brain based capital which yield high returns later in life
- a prolonged lifespan is necessary for reaping the rewards of those investments
Compared to other apes humans have
- extreme brain size
- prolonged juvenile period
- intergenerational transfers
- long life span
**all co-evolved in response to dietary shift
humans have specialized on consumption of _______ foods
calorie dense, low fibre
our intelligence associated with long developmental period
- extended period of prenatal production of cortical neurons
- extended period of myelination
- extended period of dendritic development
- cognitive development not completed until the 20s
- association with slowed aging of brain
expensive brains linked to higher _____but more difficult to acquire ______
quality, food resources
Humans unique age profile of energy production
- long dependency period
- energy production peaks in later ages
- payoffs offset the costs of the prolonged dependency period
- transgenerational transfers required to support profile
Could a species with human productivity and chimp survival profiles prosper
no
Embodied capital hypothesis
- exploration of high quality, difficult to acquire resources
- high levels of knowledge and skill
- large brain and long (and low productivity) period of development
- productivity increases with age -> lower mortality rates and greater longevity
- compensation of low early productivity during adult period via intergenerational transfers
In modern system…. embodied capital determines ____ and ______ that affect __________
- income
- social capital
- survival, growth, maintenance, reproduction
