Transcript Understanding Human Biological Variation

Understanding Human
Biological Variation
The Myth of Biological Races
The Context
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“the problem of the
20th C” WE Dubois
global racism, global
racial ideologies: the
most important
problem of the 21st C
Anthropology’s special
position
Goal of this section of the course
Learn the most recent science of “race”
 Understand the science of human
biological variation
 Examine pseudo-scientific claims about
racial difference
 Understand why racism, and the myth of
racial differences, persist despite science
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A Brief History of the Race
Concept
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Definition: subspecies
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two populations
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rarely or never interbreed,
genetically very different from one another
typological difference
500 years ago: un-thinkable
 race = essential part of the global
discourse of power, Foucault on race and sex
 race = deeply embedded in our cultural
unconscious
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“Race” science in the 19thC and
20thC
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The logic of “race science”—or scientific
racism
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Typological model
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see Stephen Jay Gould, The Mismeasure of Man
Typically three “races” (trait problem)
The methods employed
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Seeds and lead pellets
Identifying what skulls go in what groups
The Turning of the Tide
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“Papa” Franz Boas,
‘father’ of American
Anthropology
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Dubois and Boas, ~1920s
Boas: Ethnological
research on Northwest
Coast: biological traits flow
and circulate
Boas: studies of European
immigrant children skulls
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W.E. DuBois,
leading
early 20thC
sociologist
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importance of
environment
by 1960, idea of race as
biologically meaningful
category debunked
But….my experience with
this lecture
The Demise of the Race Concept in
Biology
Subspecies: clearly not the case
 3 traits
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skin color
hair texture
facial physiognomy
do not co-vary
these traits = phenotypes, NOT genotypes
where is the line?
Where to Draw a Line?
Human Population Genetics
DNA, Genes, Alleles
 Humans have
thousands of genes
 For each gene, as
many as 100
alleles*
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Simplified representation of
a human chromosome pair
 We are polytypic
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Distribution of
alleles within
populations: Gene
frequencies
* Weiss, Kenneth. 1998. Coming to Terms with Human Variation
. Annual Review of Anthropology 27: 280
Other Ways of Making “Races”
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Lactose Tolerant
People:
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Northern & Central
Europeans
Arabians
North Indians
the Fulani of W. Africa
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Lactose Intolerant
People:
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Southern Europeans
other African
Populations
East Asians
Australian Aborigines
Native Americans
Looking at traits that are strongly genetic, and
looking at gene frequencies—or the variation in
how common the allele is in various
populations
Other Ways of Making “Races”
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Arched Fingerprints:
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Looped Fingerprints
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Black Africans, Europeans
Jewish people and some Indonesians
Whorled Fingerprints
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Aboriginal Australians
Clinal or Populational?
Genetic variation between humans is low,
94% same*
 by 1940s, scientists looking at difference
as populational
 today, evidence indicates difference is
best understood as clinal, graduated
across space, with occasional
discontinuities yielding some populational
differences
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*Marks, Jonathan. 1995. Human Biodiversity: Genes, Race and History. New York:
Aldine de Grutyer
Hair color in Australia
Distribution of A Allele in world
Distribution of B Allele in E. Asia
Distribution of B Allele in Western
Europe
Distribution of B Allele in World
Distribution of O Allele in World
Genetic Variation within and Between
human populations
The genetic variation within any human
population is greater than that between
any of the purported races, and between
any two populations
 Greatest genetic variation known is among
small camps of West Africans (10-20
people), or within this small group
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Which of these athletes are closer
genetically?
The problem of thinking genetically
Genotype v. phenotype
 Human Genome Project; humans and
roundworms
 Genes, environment, proteins: complex
web yields phenotype
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(eg what genes make skin color, what genes
make hair color, what genes make eye shape)
Evolutionary Evidence
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Origins of all modern
humans from African “Eve”
“Every person’s DNA is a
mosaic of segments that
originated at various times
and in different places”
(mit website on race
science)
..reshuffled combination of
30,000 genes from many
different ancestors
stretching back for
generations..
Everyone in the world
today has pieces of ancient
African genes in them
Evolutionary Evidence, con’d
europeans
C.A.R pygmies
chinese
Zaire pygmies
melanesians
Relative genetic distance between populations
•Continuous gene flow between populations
•Differences are due largely to natural selection acting in specific
environments
•If we had to do typologies, seven or more “races” in Africa, and everyone
native to elsewhere in the world in the eighth “race”
Human Biological Variation
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Body Shape and Size
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Skin color variation
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Allen’s Rule: big appendages
Bergman’s Rule: thick bodies
melanin as protector from sun, inhibitor of
Vitamin D
Sickle cell hemoglobins and malaria
resistance
Distribution of Skin Color
“Human Nature”
Migration
 Exchange/inter-marriage/gene flow
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Perhaps these tendencies explain our
“evolutionary success”—the fact that there
are more and more of us all the time and
we live all over—kind of like
cockroaches……