Modern Humans: Biological Variation

Question 1

Paradox of Human Variation

Answer 1

A. Homo-sapiens are a young species with an existence of about 200k years.
I. Less genetic variation than other primates
II. Lots of phenotypic diversity (observable characteristics) , some important genetic diversity

Question 2

Biology’s Definition of Race

Answer 2

1. Populations (not subspecies) that are genetically or physiologically distinct
   * Applied to many different species; no human populations meet this definition

Question 3

Def. Genetic Variation

Answer 3

The difference in DNA sequences between individuals within a population.

Question 4

Examples of Genetic Variation

Answer 4

A. Immune System:
1. ABO Blood type- highly canalized ( reduction of variation), varies geographically and is linked to exposure to different diseases

B. Lactose Intolerance:
1. Cultural adaptations to consuming lactose
2. Genetic adaptations to consuming lactose: the body produces lactase (enzyme that breaks down lactose) for an individual’s entire life
3. Role of Culture: lifelong lactase is only an adaptation if your groups regularly consumes milk and other dairy

Question 5

Linnaeus & Scientific Racism

Answer 5

• Conflates physical features & moral character

“American Indians”- for example, arme described as not only possessing reddish skin, but are also choleric, paint themselves with fine red lines and are regulated by custom.

“Africans”- are described as having black skin, silky hair and flat noses and are phlegmatic, relaxed, indolent, negligent, anoint themselves with grease and governed by caprice.

“Europeans”- are white, sanguine, muscular, gentle, acute, inventive, have long flowing hair, blue eyes, are covered by close vestments and govern by law.”

Question 6

Social Darwinism

Answer 6

Darwinism in Human Fitness:

Selective Pressures
1. Diet & Nutrition
2. Disease Exposure

Fitness: The ability to survive and reproduce

Question 7

Social Darwinism

Answer 7

Fitness Distorted:

Selective Pressure
1. Social Stigmas and expectations
2. Power and hierarchy
3. Structural Violence

Fitness: the RIGHT to survive and reproduce

Question 8

Eugenetics Movement

Answer 8

Eugenetics: Improvement of Humanity

1. Genetic purity & alleviation of suffering
2. Removal of “degenerate” traits
3. Society becomes healthier, more intelligent

Question 9

Eugenetics: Ways to maintain purity

Answer 9

• Restricted marriage
• controlled immigration
• segregation
• forced sterilization
  -extermination
• Nazi rhetoric

Question 10

Polygenic vs. Monogenism

Answer 10

Polygenism is the theory that the human races have seperate origins
Monogenism theorizes that the species came from only one ancestral line or origins

Question 11

What is race pertaining to Biological race?

Answer 11

Race is a genetically distinct population

Question 12

Genetic traits…

Answer 12

Are non noncordant (ex. Not all pale-skinned people all have blond hair and blue eyes)

Question 13

Apportioning Racial Diversity

Answer 13

*Majority of allelic variation (# of allele forms on a chromosome) is between individuals, not between large populations

• 6% of humans genetic diversity corresponds to culturally-assigned racial category

Question 14

Commonly Used Racial Criteria

Answer 14

Skin Color: subjective, based on looks and not function
Facial Features
Body size/ physique
Biologically Meaningful… as an adaptation; not necessarily reflective of descent

Question 15

What is the Epidermis

Answer 15

Is the outer layer of the skin

• contains thin layers of keratinocyted (basal cells) that divide and then migrate to the skin’s surface
• lowest level of epidermis contains melanocytes (melanin-forming cell)

Question 16

What is the dermis?

Answer 16

Is the inner layer
- blood cells, nerves, hair follicles, glands

Question 17

Function of Melanocytes

Answer 17

Produces melanin granules and finger-like dendrties transport the melanin throughout the epidermis

Question 18

Melanin= Pigmentation

Answer 18

• Most people have the same # of melanocytes
• the amount , the size, the rate, and the location of melanin produced influences the degree of pigmentation
• Skin pigmentation= measure of photoreflectivity

Question 19

Golfer’s Rule

Answer 19

*Darkness of skin is correlated with humid environments which tend to occur in equatorial zones.
-Mammals or birds in the tropics appear to have black coloration
- Mammals or birds in the arctic have white coloration
- Human populations follow this general pattern

Question 20

UV Radiation effects of Lightly Pigmented People

Answer 20

Lightly pigmented people exposed to strong sunlight have clinically low levels of the essential B vitamin folate in their blood

Folate deficiency related to increased neural tube defects
- UVB radiation breaks up folate molecules

Question 21

Not Enough UVR + Too Much Melanin

Answer 21

Lack of vitamin D= bones fail to mineralize properly during development
-Osteomalacia: softening of bones

Selective pressure:
- increases infant mortality

Question 22

Cultural Cofounders

Answer 22

• Clothing in areas of high UV radiation
  
  1. Adaptive for insulating against heat stress
• Problematic for UV absorption
• Behavior that limits UV exposure in those with dark pigmentation

Question 23

Body Size: Bergman’s Rule

Answer 23

As body size increases:
> there is an increase in the amount of metabolizing tissue, therefore internal heat gain is greater
> there is an overall decrease in the surface area to mas ratio, meaning that heat loss is reduced

*Body size tends to be negatively correlated with temperature

Question 24

Body Size: Allen’s Rule

Answer 24

• The length of body extremeties is positively correlated with temperature

> Long, slender arms and legs is increased by assuming a more linear form
evaporation loss is directly proportional to the amount of exposed surfaced area

Question 25

Who is Frans Boas?

Answer 25

Founding Father of American Anthropology

> emphasized connections between human’s biology, culture, language, both past and present

Question 26

What is The Immigrant Study?

Answer 26

• tested the influence of environment on head shape & body size
  -17,821 people
• found that US-born children were taller with bigger heads

*pointed to the plasticity of bodily form & the importance of culture in shaping it
- Nutrition
- Sanitation
- Relative Safety

Question 27

How do we interpret human variation?

Answer 27

> Genetics
Environment
Culture

Question 28

Race as Identity and Lived Experience

Answer 28

-Early Socialization= early exposure to systems of racism & discrimination during brain development

Question 29

Historic “Doll Test”

Answer 29

*The results from the doll test showed that the majority of black children preferred the white dolls over the black dolls

> Segregation gave African American children a sense of inferiority