Empirical Challenges of Racial Classification
Developed by Scott Bronson
Grade Levels: 9-14
Subject Matter: Biology, Anthropology, Genetics, Geography
Time Allotment: 2-3 class sessions
Description: This lesson will help students examine their
preconceptions and assumptions about racial categories and understand
the impossibility of constructing a consistent system of human
Scott Bronson is Education Manager at the Dolan
DNA Learning Center of Cold Spring Harbor Laboratory in New York.
He is featured in Episode 1 of the series.
Most people still believe that the world's people come divided
into separate, biologically distinct groups called "races," distinguished
by physical characteristics such as skin color, eye shape, and
hair texture. The idea of race assumes that variation in these
superficial traits correlates with other innate differences, including
intelligence and aptitude - in other words, that members of one
race are fundamentally more similar to each other than to members
of another race.
Human beings across the world do in fact vary in their physical
appearance and genetic composition. And traits like skin color,
eye shape and hair texture are influenced by genes we inherit
from our parents. But do patterns of human variation map onto
"races"? Why do we classify the way we do, using some traits while
ignoring others? Is there a logically consistent way of assigning
individuals to a biological "race"?
This lesson will help students discover the fuzzy, inconsistent
nature of racial classification - including how and why patterns
of human variation defy racial categorization - and learn about
some of the hidden values and assumptions that underlie the reasons
we classify the way we do.
Students will first explore their own preconceptions about race
by sorting themselves according to which race they think they
belong to and listing the criteria they used. Students will then
be asked to re-sort themselves according to several of their own
observed genetic traits. These results will be compared within
and between "races" to explore the impossibility of consistent
human racial classification.
within-group vs. between group variation
- Confront the inconsistencies inherent in any attempt to classify
humans according to innate racial categories.
- Better understand patterns of human variation, including how
the geographic distribution of physical traits does not follow
racial lines but rather cuts across them.
- Introduce three basic concepts of human biodiversity: gradual
variation, non-concordance and within-group vs. between-group
- Understand the importance of logical consistency in scientific
reasoning and experiments.
- Contribute information to a group project.
- RACE - The Power of an Illusion, Episode 1 - The
Difference Between Us
(on video or DVD)
- RACE companion Web site www.pbs.org/race:
- Human Traits Worksheet; Sickle Cell and Skin Color Handout
ACTIVITY #1 - Articulating Preconceptions: What Do Students
Brainstorm the different races of the world and list all the
"races" across the top of the blackboard. Students might use different
and inconsistent kinds of labels for their races (see below).
This should not be discouraged.
Have students physically group themselves in the classroom according
to the race they think they belong to. When everyone has joined
a group, ask each group to generate a list of the criteria for
membership in their "race" (e.g., skin color), and post the list
on the blackboard under their respective racial label. NOTE: Some
students may resist joining any of the designated racial groups.
That's okay, but they must then add whatever label each would
apply to him or herself to the list of racial labels, even "human
As a class, briefly note and discuss any inconsistencies across
racial labels - for example, categories based on anthropology
(Mongoloid, Caucasian, Negroid) vs. color (Yellow, White, Brown,
Black) vs. geography (Asian, European, African) vs. ethnicity
(Arab, Jew, Kurd, Hmong) vs. nationality (Mexican, Puerto Rican)
vs. language (Hispanic), etc. - and similarly discuss the membership
criteria listed on the board. Are they all comparable?
ALTERNATE ACTIVITY #1 - For racially homogenous classes
Ask your students to do the "Sorting
People" activity on the companion Web site.
This interactivity challenges users to "sort" 20 people (images
provided) into five federally recognized categories. Once they
finish sorting, students learn (a) how the U.S. government would
classify these people; (b) how each person self-identifies; and
(c) each person's ancestry. Students can then move on to the "Explore
Traits" activity where the same 20 people are re-sorted according
to skin color, blood type and fingerprint type.
ACTIVITY #2: Problematizing Student Assumptions: Creating
an Inventory of Traits
Screen the first five minutes of Episode 1 - The Difference
Between Us, beginning with the opening titles (00:45 - 05:23;
DVD Scene #2) - this is Clip A. To view a complete transcript
of the episode, click here.
Stop the video and ask your students if they too believe their
closest genetic matches are with others in their own racial group.
As a class activity, ask your students to brainstorm definitions
of "race." List each definition on the board.
Pass out the Human Traits Inventory Worksheet (below), which
lists several traits influenced by our genes. Have the students
work in small groups to analyze their own physical traits and
fill out the worksheet.
|Hitchhiker's thumb (top joint can form almost 90-degree
|Skin color - Dark
|Skin color - Medium
|Skin color - Light
|Hand clasp - Right thumb on top
|Hand clasp - Left thumb on top
|Fingerprint type (click here
for examples) - Loop
|Fingerprint type - Whorl
|Fingerprint type - Arch
|Fingerprint type - Tented Arch
|Blood type A (ask parent, doctor, or clinic)
|Blood type B
|Blood type AB
|Blood type O
Have your students re-form their original "racial" groups. Then,
proceeding down the list of traits on the worksheet, ask the students
to physically re-group themselves in the classroom by each successive
trait (those with hitchhiker thumb on one side of the room, those
without on the other side, etc.).
After going through the entire list, discuss the following: What
do the students notice about the new groupings? Do any of them
match up or co-vary with their original racial groupings? How
would students divide themselves now on the basis of genetic similarity
and difference, taking into account all of these traits? Would
it be easier to categorize people according to race if we used
more traits? Why or why not?
Now, have the class re-visit the original list of membership
traits for each "racial" group generated earlier (these
should already be listed on the blackboard). Discuss the following:
Why did they choose some traits but ignore others when dividing
into racial groups? Why do we assume that traits like skin color
are more meaningful than whether or not your tongue curls or whether
or not your earlobes are attached? What do students think of their
earlier definitions of race?
NOTE: Many students may be troubled and confused as they begin
to scrutinize the "commonsense" racial categories we have all
taken for granted but never examined. This cognitive dissonance
is to be expected. You might re-assure students that we're not
claiming that race isn't "real" (see discussions of "social race"
at the end of Episode 1 and the other two episodes), but that
the biological criteria we use are fuzzy, inconsistent and don't
correspond to real patterns of human variation.
At this point, if you have a diverse class, you might want to
re-visit the common racial skin color labels (red, yellow, white,
brown). Have the class divide into groups of eight or so, and
have them compare their skin colors using the inside of their
upper arms (as is done in the film). What do they find? Are all
"Black" people really darker than all "white" people? What about
individuals from East Asian, Latino and Native American backgrounds?
South Asians? What color are they really? (This can be done even
with a racially homogenous class, but is best paired with the
"Explore Other Traits" activity in the Sorting People section
of the Web site.)
ACTIVITY #3: Mapping Traits onto Racial Categories
Have students read Jared Diamond's "Race Without Color," from
Discover Magazine (www.discover.com/archive),
which includes a discussion of how various inherited traits are
Working in small groups, have students make a chart that groups
populations into "races" for each of the following traits
(NOTE: advanced classes may also want to research these traits
in other populations for a more complete picture):
- Dark skin/medium skin/light skin
- Lactose tolerance/intolerance
- Epicanthal eye-folds/no epicanthal eye-folds
- Sickle-cell carriers/not sickle cell carriers
- Shovel-shaped incisors/other incisors
Using different colored pins, have each group of students mark
the geographical distribution of one of the traits on your classroom
map. Alternatively, photocopy a world map and have each group
mark the distribution of each of the traits on their map.
As a prelude to discussing the class's findings, ask your students
to define "genotype" and "phenotype." Does phenotype always reflect
genotype? What other factors might affect phenotype besides the
genes? Note that with the exception of suntanning on skin color,
the phenotypic traits above do closely reflect genotype. Emphasize
that very few traits are influenced by only one gene. Most traits
are influenced by many genes, interacting with each other and
with the environment in a very complex dance that scientists have
barely begun to understand.
Discuss the class's findings. What surprised students the most?
Does the geographic distribution of these traits match up and
co-vary with what we conventionally think of as races? Or do the
traits cut across racial lines?
For further discussion, have students explore the Human
Diversity section (select "Physical Appearance")
of the RACE Web site to see how some of the traits we usually
think of as racial are distributed geographically.
ACTIVITY #4: Why Racial Classification Doesn't Work - Understanding
Gradual Variation, Non-Concordance and Within- vs. Between-Group
We've now seen how difficult it is to find a consistent racial
classification system that works for everyone. Show the following
two video clips. As they watch, ask students to look for three
underlying characteristics of human variation that explain
why racial classification doesn't work.
CLIP B (5 minutes) - on skin color and gradual variation. Begins
with Alan Goodman on the difficulty of measuring race, ends with
Joseph Graves taking us on an imaginary walk from the tropics
to the pole. (22:35-28:03; DVD Scene #8 [back up 20 seconds from
the start of Scene #8 to include the statement by Alan Goodman
about the difficulty of measuring race])
CLIP C (9 minutes) - on non-concordance and within-group vs.
between-group variation. Begins with Alan Goodman talking about
concordance, ends with the narrator explaining that sickle cell
results from having ancestors who lived in malarial regions. (32:20
- 40:46; DVD Scenes #10, #11, #12)
To view a complete transcript of the episode, click here.
Before moving on to a discussion of why racial classification
doesn't work, make certain your students understand sickle cell
trait and the skin color stories told in the film. You can use
the following handouts for this.
NOTE: For an excellent lab on how selective forces affect
allele frequencies using the example of sickle cell, visit the
Genetics Project Web site: http://chroma.mbt.washington.edu/outreach/genetics/sickle/sickle-bean.html
Sickle Cell Handout
Sickle cell anemia is a hereditary disease that arises
from a single mutation (SNP or single nucleotide polymorphism)
in one of the genes that code for the hemoglobin protein
in our red blood cells. Hemoglobin carries oxygen through
the bloodstream to the body.
People who inherit two copies of the mutated hemoglobin
gene, one from each parent, get sickle cell anemia. Their
red blood cells become sticky and stiff and sometimes become
sickle shaped. These "sickled" cells tend to get stuck in
the narrow blood vessels known as capillaries, blocking
the flow of blood. Sickle cell anemia is a very painful
disease and can be life threatening.
But the larger number of people who inherit just a single
copy of the mutated gene are known as sickle-cell carriers.
They usually don't become anemic and interestingly, sickle
cell carriers tend to be resistant to malaria, a deadly
Malaria is caused by a parasite carried by the Anopheles
mosquito. After humans started practicing agriculture, the
mosquito thrived in standing pools of water that appeared
on the cleared land. Scientists believe that the sickle
cell mutation arose independently four or five different
times in human history, no more than 10,000 years ago, and
probably much more recently. Because carrying one sickle
cell gene conferred a survival advantage in areas of the
world where malaria was common, the sickle cell mutation
was positively selected and passed on in those regions.
As humans migrated, the sickle cell trait spread, not by
contagion, of course, but through reproduction. Population
geneticists call it 'gene flow' when a gene variant like
sickle cell passes from one population to another. As a
result of these historical and environmental influences,
sickle cell is commonly found in central and western Africa,
but not Southern Africa. It is also found on the Arabian
peninsula and over into India, as well as up through Turkey,
Greece, Albania, Sicily and Italy and other parts of the
Carrying the sickle cell variant of the hemoglobin gene,
therefore, is a marker not of race, but of descent from
people who once lived where malaria was common.
For a map showing the spread of sickle cell, click here
and scroll down to the map images.
NOTE: another mutation on the same gene but at a different
locus also confers resistance to malaria, and in its double
form also causes a blood disease. This disease is known
as thalassemia. Thalassemia is most common in parts of southern/southeastern
Asia and southern Europe.
Skin Color Handout
Why do we have different skin colors? Scientists can only
hypothesize at this point because the genetics of skin color
is poorly understood. But we do know that skin color tends
to correlate not with 'race' but with the amount of ultraviolet
radiation in the environment.
People in equatorial areas of the world, where sunlight
is most intense, have the darkest skin. This includes sub-Saharan
African peoples; Tamils, Dravidians and others from southern
India and Sri Lanka; Aborigines in Australia; and Melanesians
in the South Pacific. People living in areas where sunlight
is less intense, further north and south, tend to have lighter-colored
Scientists don't know why this is, but they have several
theories. One theory highlights the role of vitamins and
natural selection. The reasoning is as follows:
Dark melanin (skin color variation is controlled by the
kind and amounts of pigment in our skin called melanin)
acts as a natural sunscreen, blocking ultra-violet (UV)
radiation. Too much UV radiation destroys an important enzyme
made under the skin called folate. If pregnant mothers don't
get enough folate, their infants may be born without a full
brain, spinal cord or with other neural-tube disorders.
By this reasoning, anthropologist Nina Jablonski suggests
that dark skin would be a selective advantage in the equatorial
areas of the world because it would block more UV radiation
and thus prevent the destruction of folate (see "A New Light
on Skin Color" in Resources, below). Thus, darker-skinned
people would be better able to survive and reproduce in
On the other hand, the body needs some UV radiation to
manufacture Vitamin D under the skin. Without enough Vitamin
D, humans are prone to rickets, a crippling bone disorder
most common in young children. Scientists hypothesize that
among groups of early humans who migrated to regions far
from the equator, where there was less sunlight, those individuals
with lighter skin were better able to survive and reproduce
(because they could absorb enough UV radiation to produce
adequate amounts of Vitamin D). Thus light skin was increasingly
selected for in those areas. (Today, most of us get Vitamin
D from fish oil, cereals, and fortified milk - foods not
available to early humans until we developed fishing and
Over time, these two contrasting influences created a marked
difference in the appearance of people living in areas with
different amounts of UV radiation.
NOTE: Some people assume that dark melanin provides
a selective advantage because it protects against skin cancer
by blocking UV radiation. While dark skin does protect against
skin cancer, it does NOT provide a selective advantage.
That's because skin cancer doesn't usually manifest until
later in life, after the childbearing years. Unless a trait
affects the ability to reproduce, no natural selection will
occur and traits - positive or negative - will continue
to be passed down.
An alternative theory (favored by Darwin) suggests that
sexual selection drove the evolution of different skin colors
and the distribution of other surface traits like hair form.
According to this scenario, certain cultures (for one reason
or another) came to value dark skin while others valued
lighter skin color pigments. Individuals with the favored
appearance in a particular culture would have the most opportunities
to mate and have more children, just as peacocks with the
biggest tale feathers are favored by peahens and thus out-reproduce
other peacocks. Over time, this skewed reproduction would
result in differences between cultures that preferred different
traits. The advantage to this theory is that sexual selection
can spread a favored trait through a population very quickly,
while natural selection works more slowly.
Now, based on the film clips, ask the class to identify and describe
three characteristics of human variation that would explain why
it is so difficult to classify humans into racial boxes.
The three characteristics are:
Gradual Variation. Variation of traits is generally continuous,
with no clear boundaries between them. As Joseph Graves illustrates
in Episode 1 (through his imaginary walk), it is impossible to
say where one race ends and another begins. Because of gene flow,
groups living close to each other tend to be more visibly similar,
while groups far away tend to be less so. Geography is a better
explanation for similarity than race.
Non-Concordance. Human variation is highly non-concordant.
One trait rarely co-varies with or predicts for another. This
is because most traits are influenced by different genes, and
genes are inherited independently one from another. Knowing a
person's skin color does not help you predict other traits, such
as height, blood type, or sickle cell. As Alan Goodman says, "Skin
color or eye color or hair color is not correlated with height
or weight. And they're definitely not correlated with more complex
traits like intelligence or athletic performance." In a nutshell,
racial profiling doesn't work on a genetic level.
Within-Group vs. Between-Group Variation. Most of the
world's diversity can be found in any local population. As Richard
Lewontin first observed, on average, 85% of all human variants
can be found within any local population, be they Swedes, Hmong
or Fulani. (About 93-96% can be found on any continent, which
means only about 4-7% of human variation is explained by continental
divisions). In other words, as Lewontin points out in his book
Human Diversity, if a neutron bomb tomorrow wiped out everyone
in the world except for Nelson Mandela's Xhosa people, 85% of
the world's genetic variation would still be left, though the
remaining population would on average be darker skinned. Because
of this huge within-group diversity, knowing an individual's purported
race tells us little about his or her specific genes and traits.
ACTIVITY #5: Final Reading Assignment and Essay
As a final exercise, ask the students to read the following article
about our myths and misconceptions about racial classification
and its inherent subjectivity.
Jonathan Marks, "Scientific
and Folk Ideas About Heredity."
They may also want to read the "Go
Deeper" article in the Sorting People section of the RACE
As a culminating activity, ask students to write an essay addressing
the following questions (this essay will be used for assessment):
Consider this conventional definition of race: "The idea of race
assumes humans come divided into several distinct groups, each
of which carry a set of innate traits. Those who are members of
one race are more genetically similar to each other, and more
different from members of another race."
Is this definition scientifically sound given the results from
the student activity, the film clips and the readings? Why or
why not? What basic scientific criteria have to be met for this
definition to work? Have your ideas about race been changed by
this exercise? Explain.
Students can be evaluated based on their participation in class
exercises, the thoroughness of their research and analysis, and
their final essay. The essay should be judged according to how
well students use evidence from the exercise, the film, and background
readings to support their positions.
- 1. Read Stephen Jay Gould, "The Geometer of Race." Discover
Magazine (November, 1994). Gould tells the fascinating story
of how white people came to be named after a mountain range
in Georgia, and how German naturalist Freidrich Blumenbach's
visual model of five races became popularized and inadvertently
fueled notions of racial superiority and inferiority.
- Students can explore human genetic diversity further using
the Cold Spring Harbor Laboratories computer exercise titled
"How Unique Are You?" This exercise will calculate how many
other students, out of thousands that have participated in this
exercise, have the same genetic profile that they do. Don't
be surprised if the answer is zero. Go to the DNAI Web site
and navigate to the activity by clicking on Human Origins, then
Variation, then Interactive Variation Activity.
- Explore or discuss in class the related essay taken from
the "Go Deeper"
article associated with the "Sorting People" section of the
RACE Web site. Also read the Background Reading on the
history of the Census:
Should We Classify?
Following are the U.S. federal government's current definitions
for the racial and ethnic groups we used in the sorting activity:
- American Indian or Alaskan Native. A person having
origins in any of the original peoples of North and South
America (including Central America), and who maintains tribal
affiliation or community recognition.
- Asian. A person having origins in any of the original
peoples of the Far East, Southeast Asia, the Indian subcontinent
including, for example, Cambodia, China, India, Japan, Korea,
Malaysia, Pakistan, the Philippine Islands, Thailand, and
- Black or African American. A person having origins
in any of the black racial groups of Africa. Terms such
as "Haitian" or "Negro" can be used in addition to "Black
or African American."
- Hispanic or Latino. A person of Cuban, Mexican,
Puerto Rican, South or Central American, or other Spanish
culture of origin, regardless of race. The term "Spanish
origin" can be used in addition to "Hispanic or Latino."
- Native Hawaiian or Other Pacific Islander. A person
having origins in any of the original peoples of Hawaii,
Guam, Samoa, or other Pacific Islands. White. A person having
origins in any of the original peoples of Europe, the Middle
East, or North Africa.
Most of these categories were introduced in 1977, in response
to new civil rights laws designed to remedy discrimination.
Look closely at these definitions. Is everybody defined in
the same way? To be categorized as Native American, for example,
requires "tribal affiliation or community recognition" - a
condition of no other category. The definition for African
American includes a reference to "black racial groups" while
none of the other categories mention race. In fact, Hispanic
or Latino is defined as a "Spanish culture of origin, regardless
of race." The category Native Hawaiian or Other Pacific Islander
was only introduced in 1996 - previously, it was lumped together
What reasons might exist for defining these groups in these
seemingly contradictory ways? Are the criteria social or scientific?
Even though there's no consistently objective way to classify
people, can you think of reasons why we would want the government
to categorize or track information on racial groups? What would
happen to efforts to remedy discrimination and inequality if
we didn't have any racial data?
RACE Web Site:
Richard Lewontin, Human Diversity, Scientific American
Library, 1982, 1995
Stephen Jay Gould, The Mismeasure of Man, W.W. Norton,
Saadia Iqbal, "A New Light On Skin Color," National Geographic
Magazine Online. (http://magma.nationalgeographic.com/ngm/0211/feature2/online_extra.html)
DNA From the Beginning (http://www.dnaftb.org/dnaftb/)
DNAi Web site: (http://www.dnai.org/d/index.html)
From Mid-Continent Research for Learning and Education at http://www.mcrel.org/:
Nature of Science Standard 11 Level IV (Grades 9-12):
- Knows ways in which science distinguishes itself from other
ways of knowing and from other bodies of knowledge (e.g., use
of empirical standards, logical arguments, skepticism)
- Knows that scientific explanations must meet certain criteria
to be considered valid (e.g., they must be consistent with experimental
and observational evidence about nature, make accurate predictions
about systems being studied, be logical, respect the rules of
evidence, be open to criticism, report methods and procedures,
make a commitment to making knowledge public)
- Understands how scientific knowledge changes and accumulates
over time (e.g., all scientific knowledge is subject to change
as new evidence becomes available; some scientific ideas are
incomplete and opportunity exists in these areas for new advances;
theories are continually tested, revised, and occasionally discarded)
- Knows that from time to time, major shifts occur in the scientific
view of how the world works, but usually the changes that take
place in the body of scientific knowledge are small modifications
of prior knowledge
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