Lecture - 7 Human Variation and the Race Concept

Homo hinspace sapiens is classified as a polytypic species, meaning it consists of many local populations.
These local populations exhibit differences in the distribution of various biological traits.
Understanding how to interpret and explain this variations is a central question.

Human population variation is primarily driven by the fundamental forces of evolution:

Mutation: Changes in DNA sequence that introduce new alleles into a population.
Gene Flow: The movement of genes between populations, typically through migration and interbreeding.
Genetic Drift: Random fluctuations in allele frequencies from one generation to the next, particularly significant in small populations.
Natural Selection: The process by which individuals better adapted to their environment tend to survive and reproduce more successfully.
Nonrandom Mating: Mating patterns where individuals do not have an equal chance of mating with all other individuals in the population, which can alter allele frequencies and genotype proportions.

The translation of human variation into formal classification schemes is a relatively recent development in human history.
J.F. Blumenbach's sketches from the late 1700s represent early attempts to categorize human physical differences.

Carolus Linnaeus, in his 1758 work Systema Naturae, provided one of the first formal definitions and classifications of human 'varieties' or 'races'.
He categorized Homo hinspace sapiens into four specific varieties:
- Homo hinspace europeaus
- Homo hinspace afer
- Homo hinspace americanus
- Homo hinspace asiaticus
A Legacy of Linnaeus? The inclusion of a "race" question on the 2020 census form in the United States highlights the enduring legacy of such classification systems in contemporary society.

Linnaeus and other early classifiers not only described physical differences but also assigned specific behavioral and intellectual attributes to each supposed racial group.
Biological determinism is the concept that these behavioral and intellectual attributes are considered innate, fixed, and directly determined by an individual's biology or racial affiliation.

Samuel George Morton (1799 ext{-} 1851) was a prominent figure in scientific racism.
He was a polygenist, meaning he believed that human races had separate origins.
Morton conducted research measuring skull volume to test his hypothesis that distinct races could be ranked based on their brain size, implicitly linking larger brain size to intellectual superiority.
- Note: While specific results from Gould (1978:Table 1) are not provided in the transcript, the methodology and aim of Morton's work are clear.
Perpetuation by Early Biological Anthropologists:
- Earnest Hooton (early 20^{th} Century) was another early biological anthropologist who continued to perpetuate racial typologies.
- He developed detailed trait lists which were used to classify skulls into 3 distinct racial groups, further solidifying the concept of fixed biological races.

Franz Boas (early 20^{th} Century) emerged as a critical voice against biological determinism.
He pioneered the use of anthropometry (the scientific study of the measurements and proportions of the human body).
Research Focus: Boas compared head and body forms between U.S. immigrants and their children.
Key Finding: His research revealed great variation and plasticity within supposedly fixed racial categories. This demonstrated that environmental factors and changes across generations could significantly influence physical traits, challenging the notion of rigid, biologically determined 'races'.

The central question is: Is race a meaningful way to describe human biological variation?

Traditional racial classifications are typically done typologically.
This involves placing individuals into one discrete category or another based on a few highly visible phenotypic traits.
Commonly used traits include:
- Eye form: Such as the presence of an epicanthic fold.
- Hair form and color: Variations in texture, curl, and pigmentation.
- Head shape: Often hypothesized to be related to climate.
- Skin color: One of the most prominent and frequently used traits for racial categorization.

Determination: Skin color is determined by the amount and distribution of melanin pigment within the epidermis layer of the skin.
Reflectance: Higher amounts of melanin result in less reflectance of white light, leading to darker skin tones.
Measurement: The distribution of skin color is commonly measured by skin reflectance, which quantifies the amount of light reflected by the skin.
Best Predictor: The best predictor of skin color distribution globally is UV radiation exposure.

Equatorial Regions (High UV): Populations in equatorial regions exhibit the greatest amount of melanin.
- Protective Function: This high melanin concentration protects against harmful effects such as skin cancer and the breakdown of B vitamins (specifically folate).
Northern Latitudes (Low UV): Populations in northern latitudes generally have the least amount of melanin.
- Adaptive Advantage: Less melanin maximizes the skin's ability to produce Vitamin D from sunlight, which is crucial for bone health.
- Clinical Example: The image of Hungarian children with rickets (Larsen 2011:Fig 5.17) illustrates the consequences of vitamin D deficiency, often exacerbated in populations with higher melanin levels residing in low-UV environments or lacking sufficient sunlight exposure.

Skin color serves as an excellent example of clinal variation.
Cline Definition: A cline refers to a gradual change in the frequency of a trait or allele from one population to the next across a geographical area, forming a continuous gradient.

Grouping people into rigid biological types based on a single trait like skin color is logically problematic because skin color is a single polygenic trait (influenced by multiple genes).
Other Polygenic Traits: If one were to classify individuals based on any single polygenic trait, the categories would differ dramatically. Examples include:
- Eye color
- Hair color
- Hair form
- Head shape
- Body shape
- Height
- Tooth size
- …and countless others (ad hinspace infinitum).
The "Are you your own race yet?" exercise is designed to highlight this arbitrariness, demonstrating that if each trait defined a