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HBIO405 Evo Med Exam #1 > Human Life History > Flashcards

Human Life History Flashcards

1
Q

Life History is key characteristics that define progress through life (SG)

A

-Pattern of growth
-Development
-Maturation
-Reproduction
-Mortality

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2
Q

Why are life histories important? (SG)

A

-General trends/patterns
o Limitations, development time, energy requirements
-Human life history affects fitness and disease susceptibility
-Affects reproduction and longevity which in turn affects evolution
-Understanding underpinning mechanisms

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3
Q

Understanding 4 underpinning mechanisms for life histories

A
  1. Limitations imposed by mechanical strain on bones – if you are bigger its harder to distribute oxygen and nutrients
  2. Energy allocation – more energy b/c bigger brain, fire= more food=bigger brain
  3. Longer time required to reach larger size- elephant gestation period 2-3yrs
  4. Advantage of a larger body size is traded off against the greater risk of death during a longer maturation period
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4
Q

R vs K Reproductive strategies (SG)

A

R: small, short life span, prey, less intelligent, larger litter, reproduce early, independent early, little care for offspring, small size at birth, high fecundity
K: big, longer lifespan, predator, intelligent, smaller litter, reproduce late, dependent, care for offspring, larger size at birth, low fecundity

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5
Q

fecundity

A

of offspring and individual will have in their whole lifetime

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6
Q

Single cycle = semelparous breeding

A

-Reproduce once before dying
-High investment in mating
-Low investment in individual offspring survival
-Large # of offspring
-Ex: salmon

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7
Q

Multiple reproductive events = iteroparous

A

-High investment in offspring survival
-Long reproductive lifespan
-Trade off = fewer offspring from each mating
-humans

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8
Q

Factors affecting Current vs Future reproduction

A

-Environmental factors affect life history traits – plasticity
-Famine decreases fecundity
o Anorexia and amenorrhea (don’t get period)
-Early puberty and reduced height gain during puberty in cases of famine, childhood abuse…. Etc
o Mechanism enacted to ensure reproduction (evolutionary reason)

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9
Q

Extrinsic vs Intrinsic factors of mortality (SG)

A

-Mortality can be a driver of evolution
-Intrinsic (internal) = physiology like disease
-Humans primarily die from intrinsic factors
-Extrinsic (external)= environmental like prey/predator or accidents
-Increases in extrinsic mortality rates = promotes earlier reproduction and smaller body size
-Smaller body size = smaller offspring = so more vulnerable to prey = so higher # of offspring produced to compensate for high mortality rate

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9
Q

Longevity and Body mass (SG)

A

-Bigger body size = lower extrinsic mortality rates = longer lifespan
-Smaller body size = increased extrinsic mortality rate = shorter lifespan
-Prey = small = high extrinsic mortality = R strategy
-Predator = large = low extrinsic mortality = K strategy

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10
Q

Size vs Timing of Sexual Maturity
- 2 competing factors

A

-Investing energy into continued growth or reproduction?
-2 competing factors:
1. Adult size favors late reproduction where larger female = larger offspring and larger male = more successful mating
2. Mortality risk favors early reproduction

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11
Q

Fecundity and Lifespan (SG)

A

-Increased lifespan → increased body size → lower extrinsic mortality rates → lower # of offspring
-inverse correlation b/w lifespan and # of offspring

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12
Q

Longer lifespan and disease

A

-Natural selection doesn’t operate on disorders that develop after reproduction or if don’t affect reproductive fitness
-Longer lifespan = increased risk for developing late onset disorders (cancer, Alzheimer’s, Parkinson’s….)

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13
Q

Mortality risk influences life history

A

↑ extrinsic mortality → shorter maturity phase → smaller size and shorter lifespan →higher infant mortality (due to small size) → larger # of offspring (to compensate for high infant mortality rates)

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14
Q

Human Lifespan

A

-Low rate of extrinsic mortality factors because we have no predators and cultural & social support
-Extrinsic factors: homicide & accidents
-More energy for growth and learning leads to a prolonged reproductive phase
-Longer lifespan as we have evolved
-Increased incidence of late onset diseases b/c we are living way longer than we used to

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15
Q

Body Size (SG)
- is limited by

A

-Body size is limited by: resources, gravity, cardiovascular system, motility, nutrient availability, … etc.
-Larger you are the longer you survive
-Allometry: body size relationship to different components

16
Q

brain size in humans and life history (SG)

A

-Increased body weight = increased brain weight
-Humans have 2.5X what is expected for other primates based on our body size
-Brains have high energy consumption: 2% of body weight, 20% of energy consumption, 15% of blood flow
-Larger brains allow for more social and cultural interactions and achievements
-We have immature brains at birth, so they continue to grow post birth
-Larger brain size is associated with social groups

17
Q

How do we develop larger brains? – 2 main ways

A
  1. Grow brains for longer
  2. Grow brains faster
    (both ways) Results in: 2x as many neurons that form more synapses to perform its functions
18
Q

Human Life History Stages

A

-Neonate (birth to 2 months)
-Infancy (2- 36 months)
-Childhood (3-7 years)
-Juvenile (girls = 7-10 and boys = 7-12)
-Puberty and adolescent
-Adulthood (20 to end of childbearing age)
-Senescence (end of childbearing age to death)

19
Q

Human Life history

A

-Gestation is 280 days
-High parental investment
-Singleton (1 kid at a time)
-1 woman only has a few kids
-Long post-natal dependence
-High survival rate (in prehistoric times only 50% survived)
-Only homos have a childhood phase because it’s for brain growth
-adolescent phase only found in humans because this is where cognitive/ behavioral/social interactions skills develop

20
Q

brain during growth

A

-at 2 months in utero the brain makes up 50% of its body mass
-adults brain makes of 2% of body mass
-brain metabolism decreases (less energy needed) as brain grows bigger

21
Q

Human infancy stage

A

-rapid brain and immune development
-goes through many milestones
-after 6 months requires more than breast milk
-maternal milk as primary nutrient source
o stress from limited attachment and sensorimotor experiences
o nutrition required for neural connections
o mother reared vs formula fed chimps have affected growth of white and grey matter in the brain

22
Q

SIDS (SG for factors)

A

-western cultures at 2-3 months and during sleep
-factors for SIDS: formula fed, low socioeconomic status, premature or low birth weight, smoke exposure, non-back and lone sleeping, over heating soft bedding and materials
-mismatch infant vulnerabilities and dependencies
-campaign say to keep close contact with safe sleeping space

23
Q

Human Childhood

A

-b/w weening and 7
-constant growth: developing immune system & brain, adrenal androgen production causing mid-growth spurt, permanent teeth
-adult assistance needed: cooperative breeding, social and technical skills learned
-at 7 kids may be able to survive on their own
-unique to the Homo group to give time for brain development

24
Q

stunting (SG)

A

-sacrificing growth in favor of critical body functions
- long term effects: diminished physical & cognitive development, reduced productive capacity, poor health, increased risk for obesity
- happens early on in growth period and is irreversible
-Recommended actions to help: breastfeeding, scale up prevention, maternal nutrition, community support

25
Q

Juvenile

A

-7 to puberty (10-14 F & 12-16 M)
-Fully developed immune system
-Not as dependent on parents
-Feed themselves
-Learning social and economic skills

26
Q

(SG) Extension of period between weening and maturity
- bad
- good

A

-Risky because: predation, nutrient needs, disease, parental support lowers
-But we need it for:
1.Female size requirements (for pregnancy)
2.Social and foraging skills
3.Food competition in larger groups
4.Brain development
5.Immune system development

27
Q

Human Puberty and Adolescence

A

-Biological maturation: growth acceleration for 2-3 years, derived trait for humans, ends with epiphysial plates closing
-Adolescence is post puberty on the way to adulthood and is unique to humans to give us more time for brain growth and to learn social and communication skills
-Sex differences are in the onset and growth spurt rates where Females are 13-15 and Men 15-17

28
Q

Human Adult

A

-Completion of brain complexity
-Reproductive life 15-35 years
-Menopause 45-55: oocytes produced in fetal life decline and die

29
Q

Human Fecundity Historical pattern

A

-Having kids used to be a valuable resource (labor)
-Industrial revolution brought: more food, less work, less disease so higher fecundity rates
-Now having children is a burden and contraception had become available

30
Q

Environment and Reproduction

A

-Exposure to chemicals in our environment leads to lowering fecundity
-Endocrine disrupting chemicals like BPA can cause: increased risk for obesity/T2DM, decreased fertility & birth weight, increase cancer risk
-BPA: mimics estrogen so disrupts hormonal balance

31
Q

Senescence

A

-Menopause is not found in other species maybe because no one lives long enough to get to this stage like humans do
-Menopause causes a decline in bone strength
-Female fertility declines before menopause
-Used to have a lifespan of 35-40 but some evidence suggests 60s-70s
-Decline in fertility could be due to a longer lifespan
-Menopause may provide a fitness advantage: grandmother can help rear other kids

32
Q

Death and Birth Pattern with the Industrial Revolution

A

increased longevity + decreases mortality = bigger population

33
Q

brain growth in humans vs chimps (SG)

A

Homos have a childhood phase for brains growth and Humans have an adolescence phase to learn social/communication skills while chimps do not have either phase only have infancy, juvenile, and adult phase

34
Q

Why is breastfeeding important to the developing brain? (SG)

A

b/c breast milk is the primary source of nutrients and is required for the brain to make neural connections and it affects the growth of white/grey matter in the brain
- it can also help prevent SIDS & stunting

35
Q

How has an increased brain size affected life histories? (SG)

A

increased brain size has helped us make tools, become hunter, master fire, form social bonds and cultural developments to create communities to help us better survive

36
Q

examples of life history affecting disease risk (SG)

A
  • intrinsic mortality- diseases are a main cause
    -Longer lifespan = increased risk for developing late onset disorders (cancer, Alzheimer’s, Parkinson’s….)
  • since there is an extension b/w weening and maturity you are more susceptible to disease because immune system not fully formed
  • higher fecundity’s during industrial evolution because there was less disease
37
Q

effects of industrial revolution (SG)

A
  • more food, less work, less disease so higher fecundity rates
    -increased longevity + decreases mortality = bigger population

HBIO405 Evo Med Exam #1 (7 decks)

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