Todays Topics
Human Biological Variation
The Concept
of Race
Historical
Issues
Biology
Describing
Human Variation
Explaining
Human Variation
Please read Diamond (Ch. 31) & McIntosh (Ch. 33) for
discussion on Friday
For reaction paper #3, write on one of these articles (Due 3/25)
Origin of Modern Humans
African Origin
Early fossils in
Africa & Near East
Replaced other hominid species
e.g.,
Neandertals
Genetic Evidence
Mitochondrial DNA
Greatest
Diversity in Africa
Last Common
Ancestor 100,000-200,000 years
Human Migration
Human Biological Diversity
Race: Historical Issues
Race: Historical Issues
Classic races (usually 3 to 5)
Caucasoid:
Europe, SW Asia, N. Africa
Negroid: Native
Africans and recent descendants
Mongoloids: Asia
Native
Americans: Americas; tracing ancestry to Asian immigrants
Australoid:
Native Australians
Race: Historical Issues
Long history of anthropologists classifying people into racial
categories
Racist history
Link with
colonialism & slavery
Modeled after
Great Chain of Being
Primarily based on skin color
Race: Historical Issues
Rationalize European attitudes and treatment of conquered and
enslaved people
God-given
Natural (i.e.,
evolved)
Emphasized differences between people
Rigid hierarchies
Race: Historical Issues
Later spread from colonial situation
European
rankings
World War II
Nazis use of
bogus science
American
rankings of Europeans
Immigration Issues
Limits from
certain countries
Eugenics
Sterilization of
unfit
In US, 30 states
had eugenics laws in 1930s
Race: Historical Issues
Intelligence Studies
Craniometry
Samuel Morton (Pre-Civil War American Physician)
Studies of brain
size to show white males have largest brains
Stephen J. Gould reanalysis: Morton manipulated data
IQ Studies
Begin 1916
Influenced immigration policy in US
Extremely biased and flawed
Race: Historical Issues
Explaining present-day inequalities between racial groups
NOT consequences
of biological differences
Instead:
Historical factors
Contemporary social, economic, educational, and political circumstances
Race: Historical Issues
Race is a bad term to use because biologically inaccurate and
has baggage
Race is a social category
Census forms,
missing person reports, etc.
THIS DOES NOT DENY BIOLOGICAL VARIATION WITHIN OUR SPECIES!!
Race: Biology
Race as a Biological Category
Race = Sub-species
Remember genotype vs. phenotype
Population differences within a species based on phenotype &
usually location
Assumes
genetically distinct population
Assumes
geographically distinct population
Assumes
variation is discrete (i.e., not continuous)
Problems
Human variation complex and hard to characterize
Human species cannot be divided into natural units like
traditional races
Not true today,
especially last 500 years
Not really true
in past either
Problem of Admixture
Using genetic markers, study of Mexican-Americans
68% European
29% American
Indian
2.5% African
Increasing admixture in all groups
Often people of mixed heritage must choose one ethnicity /
social identity
May or may not
be linked to biology (genes)
Problems
Phenotype: Different classification schemes lead to different
groupings
e.g., skin color
vs. lactose tolerance vs. body proportions vs. blood proteins
Skin color: groups Africans, native Australians, South
Indians
Lactose tolerance: groups North Africans and Europeans
Infinite ways to sort variation & constant change
Independence of
traits
Problems
Genetic Diversity
Same problems as
phenotype
Humans are VERY
homogenous genetically
More variation
within populations than between
Lewontin (blood groups); Relethford (DNA)
6-10% of
variation between races
75-80% of
variation within populations
Very young species with lots of gene flow
Problems
Fails both tests for race/sub-species designation by genetics
Too few genetic
differences between races
Not separately
evolving lineages
Problem of Plasticity
Phenotype Plasticity
Genetics &
Environment Contribute to Phenotype
Example: Height
About 50%
determined by genes, 50% by environment
Secular Change in Height
Secular Change in Height
Secular change: Change over generations
Increase in stature of nearly every population in past 100 years
Large increase in Western Europe and the United States
Especially
in early 20th century (1cm/decade)
Across all
socioeconomic groups
Reach adult
height earlier
Secular trend in height has slowed or stopped in most U.S.
populations
Problem of Plasticity
Boas
Documented
Changes in Skull Form
European Immigrants and their Children
NOT change in
genes
Some kids born
in Europe and raised in US
These changes from:
Better Nutrition
Better Health /
Less Disease
Describing Human Biological Variation
Clines
A gradient; Gradual change in a trait over geographical space
Clines & Human Variation
Different traits have different clinal distributions
Reflect evolutionary
forces
Races cross cut clines
Clines are impractical, yet have biological meaning; Races have
little or no biological meaning, but easy to classify