Human Evolution Exam 2 - Kent State University

Herodotus

- "father of history"
- greek historian (484-420 BCE)

Marco Polo

- venetian historian and traveler (1254-1324 CE)

Christopher Columbus

- early european explorer
- discovered people of different lands
- discovered physical differences

Johann Friedrich Blumenbach

- typological classification based on skull morphology

Blumenbach's five races of humans skulls

- mongoloids
- malays
- ethiopians (africans)
- american indians
- caucasoids

Franz Boas

- founder of american anthropology
- skull shape could vary and was not fixed
- biological process rather than typological classification

R. C. Lewontin

- geneticist
- moved beyond skull shapes into DNA (blood groups, serum proteins, RBC enzyme variants)
- if races were groupings, their DNA should cluster according to racial categories (they do not)
- *genetic variation does not follow racial categorization*

Cline

gradual change in a phenotypic character from one population to the next, often following geographic continuum (ex. blood types and skin coloration)

Racial categories can only work if...

just a few phenotypes follow the same patterns (only a few are considered)

W.E.B. DuBois

- sociologist and civil rights leader
- health differences between americans of european background and african background simply due to social inequality, not biology

Lewontin found that...

races accounted for only 5-10% of the overall genetic diversity

One of the most important discoveries

the amount of genetic diversity within populations is greater than the amount of genetic diversity between populations

How related are homo sapiens?

99.9% related to every other human on the planet due to continuous gene flow

True or false: Races are not accurate representations of human biological variation

True

DNA microsatellite (repeats) of genome variation indicate...

migration patterns

Frank B. Livingstone said...

"there are no races, there are only clines"

Human life stages

- prenatal
- postnatal
- adult

Postnatal stage includes...

- neonatal (month 1)
- infancy (month 2 through end of 3rd year)
- childhood (3rd to 7th year)
- juvenile (age 7-10 F and 7-12 M)
- puberty
- adolescence (5-10 years after puberty)

Prenatal stage is...

40 weeks after conception

Adult stage is...

-reproductive period (sexual maturity -> much of adulthood)
- senescence (post-reproductive years and biological aging)

Human prenatal first trimester

three month period, most vulnerable environmental period of life

Genetic windows

developmental windows during a pregnancy

Teratogens

agents that can inflict disruptions, insults, and deformities during development

Germ layer derivatives

- ectoderm
- mesoderm
- endoderm

Ectoderm consists of...

- brain
- spinal cord
- nerves
- skin
- nails
- hair

Mesoderm consists of...

- heart
- kidneys
- bones
- cartilage
- muscles
- blood cells
- blood vessels

Endoderm consists of...

- lining of the respiratory system
- linings of the digestive tract
- liver
- pancreas
- bladder

Cylcopia

one eye instead of two

Shh

- sonic hedgehog gene
- divides optic field by suppressing pax6 expression in center of neural tube

Pax6

a gene that is part of a regulatory cascade involved in forming eyes, causes cyclopia

Parturition

the act of giving birth

Half of neonatal deaths occur when?

Within the first 24 hours of being born

Most neonatal deaths are caused by...

low birth weight (due to malnutrition, smoking, drinking, excessive alcohol consumption, etc.)

Life History: Growth and Development

- deciduous dentition
- weaning (end of 2nd or 3rd year)
- motor skills (in first two years)
- cognitive abilities (rapid growth rate of the brain)

Primary teeth have..

- eight molars (four on top, four on bottom)
- four canines (two on top, two on bottom)
- eight incisors (four on top, four on bottom)
(back to front)

Secondary teeth have...

- twelve molars (six on top, six on bottom)
- eight premolars (four on top, four on bottom)
- four canines (two on top, two on bottom)
- eight incisors (four on top, four on bottom)
(back to front)

Important anatomy of the tooth

first: enamel (white)
second: dentin (tanish and under enamel)
third: pulp cavity with nerves and vessels (under dentin)
fourth: cementrum (blue outline at bottom of tooth)

Brain development

- fetal brain is smooth
- by 40 weeks, the wrinkles (gyri and sulci) you have are the wrinkles you have for the rest of your life

Brain maturity at birth in rhesus monkeys

48-68% of adult size

Brain maturity at birth in chimpanzees

36-46% of adult size

Brain maturity at birth in humans

25-29% of adult size

Human brain growth

- at birth: 25-29%
- by three months: 50%
- by six years: 95%
- by twelve years: full weight/size

Epiphysis

ends of bones, separate growth (common in long bones)

Diaphysis

shaft or central portion of the (long) bone

Growth plate

- areas of growth between bones
- filled with cartilage then eventually filled with bone

Bone is...

vascular

Cartilage is...

relatively avascular

High altitude impact on growth...

- cold
- overwork
- malnutrition
- hypoxia
- UV radiation

High altitudes has...

low atmospheric pressure (lack of oxygen)

High altitude

>10,000 feet above sea level

The primary stressor of high altitude is...

hypoxia

Hypoxia

when body tissues receive insufficient amounts of oxygen

Severity of hypoxia increases as...

a person moves higher

What does hypoxia lead to?

- motion sickness
- headaches
- nausea
- loss of appetite
- fatigue
- breathlessness

Quechua men avg. height

~5'4"

Quechua women avg. height

~5'

Bone growth and fusion are largely dictated by...

genes and hormones

The amount of bone growth is strongly affected by...

the environment

Peruvian Andes qualities

- larger chest cavities than low altitude people
- restricted growth (shorter)
- larger lungs and better lung function

Tibetan women qualities

- their selection is for their alleles for high oxygen saturation in their hemoglobin
- much more resilient to hypoxic impacts

Color of oxygenated blood

bright red

Color of deoxygenated blood

deep red-purple

Indigenous adaptations

- hemoglobin becomes saturated to become more efficient (caused by extra RBC's produced)
- arteries and veins dilate to allow increased blood flow=increased oxygen (also extra RBC's)
- greater lung volume
- increase efficiency of oxygen transport

Climate adaption involving skin coloration

UV radiation from sun:
- shielded by melanin pigment produced by melanocytes
- helps synthesize vitamin D in skin

Darker skin color near..

equator and high elevations

Lighter skin color near...

poles (away from equator) and low elevation

Melanocytes produce...

pigment called melanin

Three major types of melanin

- eumelanin
- pheomelanin
- neuromelanin

Eumelanin

produces brown to black pigments (in hair, skin, etc.)

Pheomelanin

produces pink to red hues (lips, nipples, hair, etc.)

Neuromelanin

found in brain and is unresolved in what it does

Folate

- prevents a large number of neural tube defects (NTD)
- important in spermatogenesis, reduce heart defects in fetus, reduce stroke risk, DNA synthesis and repair

Vitamin D

- increases calcium absorption of the small intestine and thus makes calcium available for building bones
- prevents weakness in bones/rickets, prevents osteomalacia (soft bones), helps immune system fight viral infections, essential for calcium regulation in the body, aids the digestive system

Sunlight exposure _________ folate levels

depletes

Sunlight exposure _________ vitamin D

synthesizes

Selection for darker skin color near equator

- actions as natural sunblock to prevent skin cancer
- prevents loss of folate (vitamin B9)

Selection for light skin away from equator

- allows for vitamin D synthesis

Vitamin D synthesis

- sun exposure to the skin turns vitamin D precursor molecules into another form which is sent to the liver, changed again then sent to the kidneys
- the kidneys process further to produce a hormone that we call "Vitamin D"

Possible drawbacks for dark skin away from the equator

- not enough Vitamin D synthesis because low light conditions and so much melanin that synthesis becomes difficult

Possible drawbacks for light skin near the equator

- high skin cancer risk
- loose too much folate because skin is not dark enough to protect it

As latitude decreases, temperature ________

increases (near equator)

As latitude increases, temperature _________

decreases (away from equator)

Bergmann's Rule

- principle that animal size is heat related
- animals adapted in hot environments have less body mass (also greater surface area)
- animals adapted in cold environments have greater body mass (lower surface area)

Endotherms

warm blooded animals producing internal heat by simply living

Response to heat stress

- vasodilation
- sweating
- lower basal metabolic rate (BMR)

Vasodilation

- increased blood vessel diameter near the body's surface
- a way of getting more blood to the surface so it can cool before going back to the core of the body

Sweating

- a physiological response to release heat
- humans have an abundance of eccrine glands to produce sweat

Ectotherms

cold blooded animals

Allen's Rule

- principle that that animal's limb lengths are heat related
- limbs are longer in hot environments
- limbs are shorter in cold environments

Cold stress responses

- vasoconstriction
- shivering
- elevated BMR

Vasoconstriction

- decrease blood vessel diameter
- reduces blood flow and heat loss from the body's core to the skin

Shivering

a physiological response to generate heat

Who has a tapetum lucidum?

nocturnal animals (animals awake during the night)

Who lacks a tapetum lucidum?

diurnal animals (awake during the day)

Which primate group includes some species that have a prehensile (grasping) tail?

new world monkeys (haplorhines)

What does is mean when a primate group is monogamous?

-they look fairly similar
- no differences in size and coloration

Which primate has two offsprings (twins) at once and why did they evolve this?

- Marmosets
- they evolved this because there is heavy predation on this population

What group has a post-orbital bar?

strepsirhines

What group has a post-orbital septum?

platyrrhines and catarrhines

Strepsirhines include...

- lemurs
- pottos
- galagos
- lorises