ANT 201: Week 3

Polymorphism

Variations that exist in a population

Phenotype Plasticity

Changes to phenotype in response to environmental stressors

• body trying to maintain homeostasis

• no genetic change

• Individual level change

• acclimation, developmental, + behavioral

Adaptation

Increase in frequency of a trait as a result of natural selection

*once it starts it keeps going “adapt + keep up”

True or False:

Adaptation is not temporary and only happens at the population level

True

How is altitude an example of adaptation

Stressor: hypoxia (lack of oxygen)

• increased lung volume (chest shape)

How is altitude an example of pheno plastic changes

Stressor: hypoxia (lack of oxygen)

• developmental= slower growth, increased heart + lung capacities

• acclimatory= increased erythropoiesis/hemoglobin

• behavioral/cultural= oxygen tanks

Bergmann's Rule

Larger objects will lose heat at a slower rate than smaller objects

• Larger bodies are built for cold environments, smaller bodies are built for hot environments.

Allen's Rule

Linear objects have greater surface area than more cubic objects of the same volume

• more surface area more efficient heat loss

• large surface area= dissipates more heat

longer limbs —> more surface area —> more heat loss —> keep cool in hot env.

*vice versa for short limbs (keep warm)

Clinal Variation

Gradual change in trait frequencies over geographic space

ex: blood types

Clinal distributions tend to be impacted by

• gene flow

• isolation+/or distance

• genetic drift

• founder effect

• sometimes natural selection

  ex: smallpox

True or False:

the majority of genetic variation in human populations IS adaptively significant

False

it is NOT adaptively significant

Non-Binary Sex

Turner syndrome (1X or partial second X) and Klinefelter syndrome (XXY)

• occurs during nondisjunction when chromosomes don’t properly separate

  (extra 1 or loss of 1)

Modern Synthesis

Population-level frequencies and variation rather than a typology (race checklist)

*”modern world”—> only people currently living are affected

One-Drop-Rule

if you had even just one drop of non-white blood you were considered to not be white

Concordance

Traits showing the same geographic patterns of variation

• human variation is NON-concordance

  Ex: black people w/ blonde hair

Descrete

specific categories where you could draw a line of difference

• drawing a line on a map for groups w/ specific blood types (can’t do it)

Sickle Cell

High frequency in black populations but also common in Greece, not discrete to a specific race

• believed that it’s only tied to black people

Human Genetic Variation

Humans share 99.9% of DNA

• 90% of genetic variation within groups + 10% between groups.

Isolation-by-Distance Model

the closer you are geographically the more similar you are bound to be versus distance

Out-of-Africa Model

Most genetic diversity in humans is found in Africa and spreads out

Skulls

Attempts to show discrete differences between groups, but confirmation bias and sampling errors led to flawed results

• they don’t always properly sample + therefore can’t always be applied to the general pop.

• ignore skulls that don’t fit the set categories

Cultural Variation in Racial Classification

Racial classification changes over time due to social interpretations

• Rwandan Genocide

• Holocausts: classified Jews based on associated traits

• Irish + Italians were first not considered white

• Basketball used to be considered a Jewish-dominated sport vs. now

  • idea that some races have athletic biological advances (GET OUT)

Dangers of Biological Race Concepts

Beliefs about diseases and pain perception can lead to underdiagnosis and unequal treatment

• Sickle cell diagnosis (white girl wasn’t thought to be tested cause it considered a black disease)

• Cystic fibrosis is believed to be a European thing but found in other races but since hasn’t been studied in other races enough so they are rarely diagnosed

• Belief that black people didn’t experience the same degree of pain

An example of culture impacting Biology:

African-Americans w/ higher blood pressure

higher risk for blood pressure +/or heart disease found to be linked to groups who experience discrimination in comparison to those that didn’t experience this

Melanin

pigment that helps determine skin color

Melanocytes= cells that produce melanin

• natural protection from UV rays

Skin color varying by latitude

(distance from the equator)

populations near the equator are more likely to have darker skin versus those farther from it

Hypothesis on Melanin

helps prevent skin cancer

Darker skin—> protection from UV rays —> less risk of skin cancer

*Doesn’t make sense from a selective standpoint

Folic Acid Hypothesis

Melanin protects against low folic acid levels caused by UV rays

• birth defects

• decreased sperm production

Vitamin D Hypothesis

UV helps with Vitamin D production + nutrient absorption

Deficiencies lead to

• increased risk of some infection

• rickets

+Too much melanin in low UV areas (far from the equator) leads to Vitamin D deficiency