Human Biological Variation and the Social Construct of Race
Evolutionary Context of Homo Sapiens
Modern Ancestry: Current humans belong to the species Homo sapiens. Humans share an ancestry with archaic Homo sapiens and are considered cousins to the Neanderthals.
Extinction of Neanderthals: Neanderthals were the last major hominid species to coexist with modern humans. While the exact cause of their extinction is not entirely known, evidence suggests that the superior intellect, brain capacity, and language abilities of modern humans allowed them to outcompete Neanderthals.
Modern Variation: The focus of contemporary anthropology is on variation within modern human populations, specifically analyzing the biological and social dimensions of categorization.
The Concept and History of Race
Biological vs. Social: In the United States, race is often perceived as having biological origins, but scientific analysis shows it is a social tool used to categorize and classify Homo sapiens. Categories of race differ across different countries and populations.
Ancient Conceptions: The classification of humans based on outward appearance is not a modern phenomenon. * The Ancient Greeks categorized humans based on visual traits. * The word Ethiopian originates from a Greek term meaning "the scorched ones." * Most cultures have methods of classifying groups based on physical appearance, though the frameworks vary significantly (e.g., Brazil has far more categories for ethnicity and race than the U.S.).
Eugenics and Natural Selection: * Darwin’s Influence: Although Charles Darwin did not intend for his theories to be used this way, his concept of natural selection was co-opted to fuel the Eugenics movement. * Survival of the Fittest: This term was not coined by Darwin but by Herbert Spencer; Darwin later accepted its use. This idea was flawed when applied to humans to suggest some individuals were more "fit" to reproduce than others. * The Eugenics Movement: Peaking in the and , this movement advocated for sterilization or elimination of certain people to stop their progeny from reproducing. Notable historical examples include the Holocaust in Nazi Germany and similar eugenics policies within the United States.
US Census Bureau Definitions of Race
Purpose: The U.S. Census Bureau utilizes specific racial definitions for diversity tracking, funding, and demographic studies. These categories are based on tradition rather than biological science.
Standard Categories: * White: A person with origins in the original peoples of Europe, the Middle East, or North Africa. This includes individuals of Arabic, Iranian, Israeli, or Jewish descent. * Black or African American: A person with origins in any of the "black racial groups of Africa." The census lacks a formal scientific definition for what constitutes a "black racial group" and does not clearly differentiate this from North African populations. * American Indian or Alaska Native: A person with origins in the original peoples of North and South America (including Central America) who maintains tribal affiliation or community attachment. This is a dual requirement often tied to legal benefits and the Dawes Rule (blood quantum). * Asian: A person with origins in the Far East, Southeast Asia, or the Indian subcontinent. Examples include Cambodia, China, India, Japan, Korea, Malaysia, Pakistan, the Philippine Islands, Thailand, and Vietnam. * Native Hawaiian or Other Pacific Islander: A person with origins in any of the original peoples of Hawaii, Guam, Samoa, or other Pacific Islands.
Ethnicity vs. Race: * Hispanic/Latino: This is classified as an ethnicity, not a race. An ethnicity is a group tied to a linguistic or cultural past (e.g., Spanish or Portuguese-speaking). * Individuals identifying as Hispanic or Latino can be of any race (White, Black, Asian, Native American, or a mixture like Mestizo).
Human Migration and Genetics
Mitochondrial DNA (mtDNA) and Y-Chromosome Research: Both genetic markers trace all Homo sapiens back to a singular origin in Africa, supporting the Replacement Model (or Out-of-Africa model).
Haplogroups: These are population groups tied together by specific genetic markers (mutations). Some scientists suggest using haplogroups as a more accurate alternative to the social construct of race.
Migration Waves: * Internal African Migration: Occurred between and years ago. * First Wave Out (Southern Route): Took place approximately to years ago. These humans traveled through the Arabian Peninsula, India, and Southeast Asia to reach Australia and Papua New Guinea. * Second Wave Out: Occurred roughly to years ago, moving into Central Asia and eventually Europe. * Peopling of the Americas: Estimated to have occurred as early as to years ago, primarily via the Beringia land bridge between Russia and Alaska.
Case Studies in Human Variation
The Papua New Guinea Paradox: Individuals from Papua New Guinea may superficially resemble African populations due to dark skin and curly hair. However, they are genetically more dissimilar to Africans than Europeans are. This is because their ancestors left Africa roughly years before the ancestors of Europeans did.
The Ainu of Japan: An indigenous ethnicity in Japan that possesses physical traits (such as facial hair and features) that often lead observers to mistakenly guess they are of Nordic or Scandinavian descent. They have a history of ethnocide (the destruction of a culture) through forced assimilation and language suppression by mainstream Japanese society.
The Basque: A group in Spain/France with a unique language and culture. Under the regime of Francisco Franco, they faced similar cultural suppression aimed at eradicating any language that was not Castilian Spanish.
Aboriginal Australians: Some children in Aboriginal Australian populations possess a gene that gives them very light blonde or white hair, which typically darkens as they age.
Biological Determinants of Physical Traits
Skin Color: This is a clinal distribution (geographic gradient). It is primarily determined by Melanin, which blocks UV rays. * High UV (Equatorial regions): Darker skin is an adaptation to block intense UV rays while still allowing for some Vitamin D processing. * Low UV (High altitudes/Poles): Lighter skin is an adaptation to maximize the absorption of weak sunlight to synthesize Vitamin D. * Vegetation Cover: In areas like the Amazon or Congo, populations may have slightly lighter skin due to heavy tree cover providing natural protection from the sun.
Eye and Hair Color: While dark hair and eyes (brown) were likely the ancestral state in Africa, variations like blue or green eyes and blonde or red hair likely emerged and stabilized through sexual selection rather than survival-based natural selection.
Epicanthic Eye Folds: Common in Asian populations but also found elsewhere, such as the San people of Southern Africa. Its survival advantage is debated (possibly linked to diffuse light in snowy environments), but it may also be sexually selected. Genghis Khan is cited as a historical figure whose massive progeny helped spread this trait across Central Asia.
Internal Genetic Variation
ABO Blood Type System: * Type O: The most frequent allele globally. It appears at nearly frequency in Native American populations in Central and South America. * Founder’s Effect: This high concentration of Type O is likely due to the Genetic Bottleneck or "Gilligan's Island effect," where a small initial group of migrants populating the Americas carried only specific alleles.
Lactose Intolerance: * Normal State: Most mammals, including humans, are naturally lactose intolerant after weaning, as the production of the enzyme lactase stops. * Mutation: Lactose tolerance (the ability to digest lactose) is the actual mutation. This developed in populations with a history of Pastoralism (herding milk-producing animals like cows, goats, or sheep). * Geographic Distribution: High tolerance is found in European and some African populations. High intolerance is found in Native American and many Asian populations where dairy culture did not historically exist.
Genetic Diversity in Africa: Africa contains the highest level of genetic variation of any continent. Because humans lived in Africa longer than anywhere else, the population has had more time to accumulate mutations and diversify.
Ecological Rules of Body Types
Bergmann’s Rule: Relates body Mass to climate. Larger, thicker bodies (higher mass) are found in colder climates to conserve heat, while smaller bodies are found in warmer climates to dissipate heat.
Allen’s Rule: Relates Appendages (limbs) to climate. Shorter limbs are characteristic of cold-climate populations (to prevent heat loss), while longer limbs are found in hot-climate populations.
Questions & Discussion
Question (Instructor): Looking at the black-and-white photo of a man with dark skin, curly hair, and a septum piercing, where do you think he is from?
Student Answers: India, Africa, South Asia, Australia (Aboriginal), African American, New Zealand, Venice (Boardwalk).
Response: Most people guess Africa. However, he is from Papua New Guinea. He is genetically more distant from Africans than a European person is, despite outward appearances. Septum piercings are traditional in many cultures, including those in Africa and Papua New Guinea, and are not unique to one region.
Question (Instructor): Where do you think this man in the robes [the Ainu man] is from?
Student Answers: Australia, Scandinavia/Nordic countries, Egypt (Pharaoh).
Response: He is Japanese, specifically of the Ainu ethnicity. His facial features and hair often lead to him being misidentified as European.
Participation Question/Exercise: Connect the following terms to their definitions: Bergmann’s (Body mass = B), Allen’s (Appendages/Limbs = A to A).