Lecture Notes: Human Migration, Behavioral Modernity, Human Variation and Evolution, Forensic Anthropology

Human Migration and Ancestry

• General Migration Patterns of Homo sapiens sapiens:
  • Understanding major migration events and the evidence supporting them is crucial for tracing modern human ancestry.
  • Key evidence includes:
    • Skhul Cave findings: early modern human fossils outside of Africa.
    • Mitochondrial Eve: the most recent common female ancestor for all living humans.
• Mitochondrial Eve: Represents the matrilineal most recent common ancestor (MRCA).
  • Estimation: Estimated based on the mutation rate of mitochondrial DNA.
  • Implications: Indicates that all humans share a relatively recent common ancestor.
  • Common Misconceptions: Does NOT mean she was the only woman alive at the time, nor does it negate the possibility of multiple waves of human migration or admixture with other hominin populations.

Middle Stone Age/Upper Paleolithic AMH Cultures

• Behavioral Modernity: Refers to the suite of behavioral and cognitive traits that distinguish modern humans from earlier hominins.
  • Key Characteristics: Symbolic art (cave paintings, figurines), advanced tool technology, personal ornamentation, ritualistic behavior, and complex social structures.
  • Time Frame: Emerged in Africa ~100,000-60,000 years ago and later in Europe.
• Competing Hypotheses:
  • Upper Paleolithic Revolution/Creative Explosion: Proposes a sudden and rapid emergence of behavioral modernity around 40,000-50,000 years ago in Europe.
  • Continuity Hypothesis: Suggests a gradual and incremental accumulation of modern human behaviors over a longer period, starting in Africa.
  • The correct hypothesis informs our understanding of human behavior and brain evolution.

Role of Climate in Behavioral Modernity

• Variability Selection: Theory suggesting that periods of significant climate fluctuation favored individuals with greater behavioral flexibility and adaptability.

Human Variation and Evolution

• Level of Variation: Biological anthropologists focus on polymorphic traits (traits with multiple forms) to study human variation.
• Anthropological Approaches to Human Variation:
  • Racial Classification: Categorizing humans into discrete racial groups based on observable traits.
    • Historical Context: Prevalent during the 18th-20th centuries (Renaissance/European exploration & expansion).
    • Linnaeus, Anthropometry, Blumenbach, Environmentalism: Key players and concepts during its development.
    • Example: Blumenbach's classification of humans into five races based on skull morphology.
  • Explanatory Approaches: Focuses on understanding the causes and patterns of human variation.
• History of Thinking About Race:
  • Pre-Renaissance: Limited understanding of human variation.
  • Renaissance/European Exploration & Expansion: Increased awareness of human diversity, leading to attempts at classification.
  • 18th Century: Development of racial typologies based on anthropometry and environmental influences.
    • Linnaeus: Developed a hierarchical classification of humans, with Homo sapiens divided into subspecies based on geographic location and perceived behavioral traits.
    • Anthropometry: Measurement of human body dimensions (e.g., skull size) used to classify individuals into racial groups.
    • Blumenbach: Classified humans into five races based on skull morphology: Caucasian, Mongolian, Ethiopian, American, and Malay.
    • Environmentalism: Belief that environmental factors (e.g., climate, diet) are the primary drivers of human variation.
  • 20th Century: Rise of eugenics and scientific racism, followed by a rejection of racial typologies.
    • Eugenics: A pseudoscientific movement that advocated for selective breeding to improve the genetic quality of human populations.
    • Boas’s Immigrant Study: Franz Boas demonstrated that skull shape was influenced by environmental factors (nutrition), undermining the idea of fixed racial types.
    • 1940s – 1950s: The Holocaust and colonialism exposed the dangers of racism and led to a re-evaluation of racial concepts.

Race, Social Race, Ethnicity, and Racism

• Race: A social construct that categorizes people based on perceived physical differences.
• Social Race: The way race is defined and understood within a specific society.
• Ethnicity: Refers to shared cultural heritage, language, and traditions.
• Racism: Prejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one's own race is superior.
• Race vs. Ancestry: Race is a social construct, while ancestry refers to a person's genetic origins and lineage.

Phenotypic Racial Traits

• Phenotypic traits (e.g., skin color, hair texture) have been used to define racial categories.
• Skin Color: Particularly skin color, is correlated with colonialism and race-based systems of enslavement.

Human Adaptation and Adaptability

• Phenotypic Plasticity: The ability of an organism to alter its phenotype in response to environmental conditions.
• Genetic Pleiotropy: When a single gene affects multiple phenotypic traits.
• Plasticity as a Functional Adaptation: Allows humans to cope with diverse environments.
• This understanding is crucial for interpreting relationships between human phenotypic variation, environmental differences, and genetic differences between human populations.

Impact of Race on Humans

• Race, as a social construct, affects humans through:
  • Stress: Experiences of discrimination and prejudice can lead to chronic stress.
  • Embodiment of Lived Experiences of Systemic Racism: The cumulative impact of racism on physical and mental health.
  • Health Disparities: Disparities in life expectancy, disease rates, and access to healthcare.
    • Coronavirus Illness and Death: Example of how racial disparities can exacerbate health outcomes during pandemics.

Biological Basis of Race

• There is no biological basis to race.
• Human variation is not racial; it is clinal and continuous.
• Clinal Variation: Gradual change in a trait across a geographic gradient.
• Continuous Traits: Traits that vary along a spectrum (e.g., height, skin color).

Evolution of Skin Color

• Purposes of Skin: Protection from UV radiation, regulation of body temperature, and synthesis of vitamin D.
• Melanin: A pigment that absorbs UV radiation and protects against skin damage.
• Skin Pigmentation as an Evolutionary Balancing Act: Balancing the need for UV protection with the need for vitamin D synthesis.
• Archaeogenetic Evidence: Cheddar Man's ancestry, descendants, & phenotype provide insights into the evolution of skin color in Europe.
• Advantages & Disadvantages of Skin Color in Different Latitudes:
  • Vitamin D synthesis: Lighter skin is advantageous in higher latitudes with less sunlight.
  • Rickets: Vitamin D deficiency can lead to rickets, a bone disease.
  • Sunburn: Darker skin is advantageous in lower latitudes with intense sunlight.
• Link Between Global Distribution of Skin Color/Pigmentation & UVR: Skin pigmentation is strongly correlated with UV radiation levels.
• Evolution of Skin Color: General time frame for key events and causes of these evolutionary events and trends.
• The general time frame would include early humans in Africa having darker skin pigmentation which then evolved to lighter pigmentation as humans migrated to areas with less UVR.

Technology, Culture, and Evolution

• Extrasomatic Adaptations: Technology and culture are extrasomatic adaptations that allow humans to adapt to their environment.
• Technology, culture (extrasomatic adaptations) evolve and influence human evolution.

Ongoing Human Evolution

• Humans are still evolving, based on the current definition of evolution.
  • Evolution: Change in allele frequencies in a population over time.
  • Evidence:
    • Lactose Intolerance: The ability to digest lactose in adulthood evolved relatively recently in some populations.
    • Loss of Wisdom Teeth: A trend towards fewer or no wisdom teeth.
    • Decreasing Brain Size: Some evidence suggests a decrease in average brain size in recent human history.

Forensic Anthropology

• Forensic Anthropology: The application of anthropological methods to the identification of human remains in a legal context.
• What Forensic Anthropologists Can and Cannot Do:
  • Can: Determine sex, age, stature, and ancestry of skeletal remains; identify trauma and disease.
  • Cannot: Determine the exact cause of death or specific details of the crime.