Chapters 13 & 14: Biological Anthropology

Race (biological definition – outdated)

A supposedly genetically distinct, usually geographically isolated, population within a species.

Race (social definition)

A socially constructed system of classification that assigns meaning and value to physical differences.

Human Variation

The genetic and phenotypic differences among human populations, shaped by evolutionary forces like mutation, natural selection, gene flow, and drift.

Discrete Races Myth

The false belief that humans can be divided into clear, non-overlapping groups.

Arbitrary Categories

Racial categories are inconsistent (e.g., “Black” vs. “Hispanic”) and often shaped by colonization and politics.

Biological Determinism

The mistaken idea that differences in behavior, intelligence, or social status are rooted in biological/racial differences.

Typological Thinking

The outdated view that humans can be classified into fixed “types.”

Carl Linnaeus (1707–1778)

Classified humans into 5 racial categories, assigning positive traits to Europeans and negative ones to others.

Samuel Morton (1799–1851)

Collected skulls and used craniometry to falsely link skull size to intelligence, reinforcing racial hierarchies.

Craniometry

Pseudoscientific measurement of skulls to categorize races and infer intelligence/behavior.

Polygenesis

The (debunked) idea that races had separate origins.

Monogenisis

The idea that all humans share a common origin (supported by Darwin and modern science).

American Eugenics Movement

Used Darwin’s ideas incorrectly to justify selective breeding, sterilization, anti-immigration laws, and racial segregation. Influenced Nazi racial policies.

Physical Anthropology (1950s)

Shifted focus from classifying races to studying evolutionary processes.

UNESCO Statements on Race (1950–1970s)

Scientific consensus that race is not a biological reality; racism has no scientific justification.

How much genetic variation exists within populations?

85%

How much genetic variation occurs between populations within regions?

9-10%

How much genetic variation occurs between “so-called” races?

6%

Clinical Distribution

Traits (like skin color or blood type) vary gradually across geography, not in discrete blocks.

Skin Color

A reflection of UV radiation

Founder Effect

Reduced genetic variation in populations descended from a small group of ancestors.

Hardy-Weinberg Principle

Genetic variation is maintained within populations unless evolutionary forces act on it.

Weathering Hypothesis

When chronic exposure to racism and stress accelerates biological aging in marginalized populations.

Biocultural Anthropology

Examines how biology and culture intersect (e.g., racism’s effects on health).

Genome

The complete set of genetic material in an organism

Photolysis

Breakdown of molecules due to exposure to light, especially UV radiation

Folic Acid (Folate)

A B vitamin essential for central nervous system development: deficiency causes pregnancy complications, reduced sperm production, and neural tube defects

Vitamin D Synthesis

Production in the skin where UV light interacts with a cholesterol-like substance in the epidermal cells (vital for calcium metabolism and bone/ teeth development

Rickets

Disease in children caused by vitamin D deficiency, leading to impaired bone mineralization, bowed legs, and pelvis/teeth issues.

Epidermis

Thin outer layer of skin tissue

Dermis

The thick inner layer of skin containing blood vessels and hair follicles

Keratinocytes

Skin cells that produce keratin, providing protection against water loss and abrasion.

Melanocytes

Specialized skin cells that produce melanin

Melanin

Dark brown pigment produced in the skin; protects against UV damage and the main contributor to skin color

Hemogoblin

Blood protein that gives skin a pinkish tint

Keratin

Yellowish protein found in skin and hair

Dark Skin

Results from synthesis of large amounts of melanin

Light Skin

Results from synthesis of smaller amounts of melanin

Freckles

Localized, higher concentrations of melanin

Melanosomes

organelles found in melanocytes (pigment cells) that produce, store, and transport melanin

SLC24A5

A gene strongly linked to variation in skin color

A allele

gene that contributes to lighter skin

G allele

gene that contributes to darker skin

Balanced Polymorphism

stable polymorphism (occurrence of 2 or more different phenotypes) in a population, in which natural selection prevents any of the alternative alleles from becoming fixed or lost.

heterozygote advantage

A selection against both alleles in homozygous condition, and a selective advantage of the heterozygous condition

Bergman’s Rule

Individuals living in colder habitats tend to have larger body sizes: less heat lost through body surface

Allen’s Rule

Extremities tend to be longer relative to body size in warmer climates to dissipate heat

Assortative Mating

Non-random mating where individuals with similar genotypes are more likely to mate, increasing homozygosity.

Null Model

A baseline model (like HWE) assuming no evolutionary forces; used for comparison against observed data.

Reproductive isolating mechanisms

General term for all barriers (pre- and postmating) preventing gene flow.

Ecological Species Concept

Species defined by exploiting a unique ecological niche

Evolutionary Species Concept

Species defined as distinct evolutionary lineages with their own identity through time.

Morphological species concept

Species distinguished by anatomical similarities/differences (useful in fossils, but limited).

Lineage

A sequence of populations that share a common ancestor

Niche

How a species makes a living (diet, habitat, ecological role).

Splice Variance

Process where different combinations of exons are joined, producing multiple proteins from a single gene.

Introns

Non-protein coding regions of DNA that are transcribed but not translated.

Pseudogenes

Nonfunctional DNA segments resembling real genes but unable to code for proteins.

Variable Number Tandem Repeats (VNTRs) / Short Tandem Repeats (STRs) 

Repeated DNA sequences used in genetic fingerprinting.

Transcriptome

The full set of mRNA molecules encoded by the genome.

Proteome

The full set of proteins produced from the genome/transcriptome.

Central Dogma

Flow of genetic information: DNA → (transcription) mRNA → (translation) protein.

Population Genetics

Study of allele, genotype, and phenotype frequency changes in populations using quantitative methods.

Population

Group of organisms capable of interbreeding, usually choosing mates within the group.

Gene Pool

Total sum of alleles in a population.

Evolution

Change in allele frequencies in a population from one generation to the next.

Genetic Equilibrium

No change in allele frequencies; no evolution occurring.

Mechanisms of Evolution

Migration, mutation, genetic drift, selection, non-random mating.

Hardy-Weinberg Equilibrium (HWE)

Null model predicting allele/genotype frequencies if no evolutionary forces act.

Hardy-Weinberg Equations

p + q = 1 and p² + 2pq + q² = 1.

Microevolution

Small genetic changes within a species (e.g., allele frequency shifts).

Macroevolution

Large evolutionary changes over time, including speciation.

Species

Real biological categories, not abstract; recognized by distinct traits and reproductive boundaries

Biological species concept

Species are groups of interbreeding populations reproductively isolated from others.

Reproductive isolation

Prevention of gene flow between populations via barriers.

Premating isolating mechanisms

Habitat, temporal, behavioral, mechanical incompatibility.

Postmating isolating mechanisms

Sperm-egg incompatibility, zygote inviability, offspring sterility.

Adaptive radiation

Diversification of a single lineage into many niches

Grandualism

Evolutionary change via slow, steady accumulation.

Punctuated Equilibrium

Long periods of stasis with short bursts of rapid change.

Anagenesis

Linear evolution within a lineage, leading to chronospecies.

Cladogenesis

Splitting of one lineage into two or more distinct lineages.

Systematics

Study of diversity of life and evolutionary relationships.

Taxon

Group of organisms assigned to a classification level.

Taxonomic Ranks

Kingdom, Phylum, Class, Order, Family, Genus, Species

Homology

Similarities due to shared ancestry.

Analogy (homoplasy)

Similarities due to convergent evolution, not common ancestry.