Molecularization of Race

Understanding Race

Neo-Darwinism - combines Darwin’s concept of natural selection with Mendel’s ideas on heredity; undermines the concept of biological race; recognizes all humans are a single species

  • Developed due to issues of “biological species” concept

Clines - pattern of gradually shifting frequency in phenotypic trait from population to population 

  • Don’t cluster in overlapping patterns, as biological race concepts assumed

Molecularization of race - revisions that connect race and biology

Species - distinct segment of evolutionary lineage

Phylogenetic species concept - identifies species based on a set of unique features that distinguish their members from other, related species

Reticulation - when members of populations are separated, then merged together and reproduce at a later time

  • Reticulation links anatomically modern humans and Neandertals

  • Occurs within species

  • Even if organisms from different species mate with one another, the species boundaries do not dissolve

  • Ex: horses and donkeys make mules, but mules are infertile so the species boundary is not affected

Gene pool - all of the genes in the bodies of all members of a given species

Gene frequency - how often variants of a specific gene occur within a population

Population genetics - measures stability or change in gene frequencies of populations over short periods of time

Polymorphous - alleles that come in a range of different forms

  • Polymorphic alleles account for most genetic variation across populations

  • Ex: A, B, O blood types (found in all human pops. but frequency is different)

  • Private polymorphism are alleles found in genotypes of some but not all members of a particular population

  • Ex: diego antigen; 60-90% of members don’t have

In terms of genetics, race makes no sense

  • More genetic variation within racial groups than between them

  • No deep underlying biological differences between racial groups

Human variation

  • Older concepts of “race” emphasized phenotypic variation

  • Individuals in tropical populations closer to equator had selective advantage over individuals with light pigmentation

  • Cline maps examine single traits through the entire human species

    • Maps reveal that the trait distributions do not coincide in ways that neatly divide into subpopulations

  • Nothing in nature aligns with the biological concept of race

Four evolutionary processes

  • Natural selection and mutation can alter gene frequencies

Gene flow - movement of genes from one population to another

  • Ex: european colonizers breeding with indigenous people

Genetic drift - random changes in gene frequencies from one generation to the next caused by sudden reduction in population size as a result of disaster, disease

  • Bottleneck effect - genetic drift of populations suddenly reduced in size by disease or disaster

  • Founder effect - small subgroups that establish themselves apart from larger populations

  • Inbreeding increases population proportion of homozygous combinations of alleles

    • Also reduces genetic variation

Microevolution

  • Cultural factors play a role in reproduction with certain populations

  • Hemoglobin is a famous mutation favored by natural selection

Balanced polymorphism - heterozygous genotype is fitter than either of the homozygous genotypes

  • Genetic flow and genetic drift can be included in discussions with niche construction

Gene Interaction

  • Pleiotropy and polygenic explain how discrete genes influence phenotypic traits

Major effect gene - a gene at one locus whose expression has a critical effect on the phenotype

Phenotypic plasticity - physiological flexibility that allows organism to respond to environmental stressors, like temperature changes

  • Humans use plasticity of genes to adapt to environmental conditions

    • Ex: homeostatic processes

Acclimatization - change in the way the body functions in response to physical stress

  • Ex: shivering; go inside, put more clothes on

Epigenetic marks - chemical modifications in DNA that are associated with changes in the way genes are expressed, and are essential for normal development

  • Align with Darwin’s theory (genetic variation must be present)

Skin Color

  • Adaptive and related to the degrees of ultraviolet radiation

  • Skin color evolved independently from human populations inhabiting similar environments

    • Useless indicator race

  • Positive and negative consequences of sun exposure

2 skin clines:

  1. Dark skin at equator, adaptive protection against sun damage

  2. Light pigmentation, farther from equator, favors vitamin D production

  • Culture influences levels of pigment and vitamin D production

Intelligence

Multiple types of intelligence:

  1. Logico-mathematical

  2. Interpersonal and intrapersonal

  3. Musical 

  4. Spatial

  5. Naturalist 

  • IQ tests do not demonstrate racial differences

    • Poor way of measuring intelligence because there's no measurability to intelligence

    • Other factors can affect test-taking: hunger, exhaustion

    • Score of IQ tests is more predicted by social class and educational background than by race

Molecularization of Race

  • 1960-70s, there was no biological explanation for race

  • Examines the genotypic variation

Human Genome project (2003) - aimed to identify all genes in human DNA and determine the sequences of base pairs in human DNA; all while addressing legal and social issues

  • If a genetic disease shows up in genomes of particular race, other members of said race might be at risk for disease

  • Transition of race from phenotype to genotype after sickle cell anemia 

  • Modern technology assessing race assumes that everyone has mixed ancestry, which is not accurate

  • Biocultural approaches reveal how social differences can become biology since they shape the nervous system

  • Phenotypes are shaped by genes and environment

  • Genetic explanation doesn’t consider the effects of growing poverty and political marginalization

  • The number of genes possessed by an organism is not coupled with phenotypic complexity

Formal models - mathematical formulas to predict outcomes of particular kinds of human interactions under different hypothesized conditions

  • Ex: sociobiology

Predicting Human Evolution

  • Explains survival at any cost to be moral because it’s “natural”

  • Humans have options that don’t exist for other animals

    • Cultural adaptations based on learning, even when biological reproduction is absent

  • Genotypes, phenotypes, and environmental factors cannot predict how to live

  • Debate between physical life (survival and reproduction) and meaningful life (goals, existentialism)