04/26/12
Name:
BIOL 116 Section:
Before the lecture starts, answer the following.
1. How would you define race?
2. How many races do you think there are?
3. What are they?
4. How do you decide which race someone belongs to?
5. Where do your ideas about race come from? What are the sources of your information?
6. Write the race below the picture of each of the following children:
Genetic Diversity II
Why We are So Similar
The Meaning of Race from a Biological Perspective
I. The Science of Classification
II. Brief History of Human Racial Classification
III. Traditional Racial Groupings
IV.Human Genome Project
V. The Power of an Illusion
I. The Science of Classification
A. Classification Hierarchy
TAXON / HUMAN / SHARED CHARACTERISTICSKingdom / Animalia / multicellular, movement, eat & digest other organisms
Phylum / Chordata / notochord (backbone)
Class / Mammalia / hair, mammary glands
Order / Primates / fingers, flat nails
Family / Hominidae / upright posture, flat face, large brain
Genus / Homo / double curved spine, long life span, long youth
Species / Homo sapiens / chin present, high forehead, thin skull and bones
Races, Types,
Strains, Groups, Subspecies / ? Skin color, geographic location, hair texture, facial features?
C. There are ‘rules’ so that classification is performed scientifically.
1. The classifier must choose the trait(s) used to assign individual organisms
into specific groups.
The traits chosen will define that group.
(i.e., “You are a member of this particular group if you have *this* trait.”)
a) All of the members of a group must share the trait(s) chosen to define the group, and the chosen trait(s) cannot be found in individuals placed in a different group.There should be ‘pure’ groups.
b) If the traits chosen form a meaningful classification, it should be clear into which group allindividuals should be found.
2. Groups that are tightly defined follow the above rules for classification. Tightly defined classification schemes are scientifically (biologically) valid.
D. There is some level of subjectivity when scientists classify any organism:
What characteristics do you use when separating groups?
When do you stop separating(Lumpers and Splitters)?
II. Brief History of Human Racial Classification
A. Ancient peoples: Greeks had no word for ‘race’.
B. 1500-1600s: Trade routes became established
C. Carolus Linnaeus (1707-1778)
1. Americanus
2. Europeaeus
3. Asiaticus
4. Afer
D. Johann Friedrich Blumenbach (1752-1840)
E. 2000 U.S. Census
The most profound change to the question on race for Census 2000 is that respondents are allowed to identify one or more races to indicate their racial identity.
The minimum categories for race are now:
American Indian or Alaska Native
Asian
Black or African American
Native Hawaiian or Other Pacific Islander
White
Some Other Race (Intended to capture responses such as Creole)
III. Traditional Human Racial Groupings
A. The traits used for traditional racial groupings primarily are based on outward appearance.
1. Skin color: Background
Skin color is determined by the amount and type of the pigment melanin in the skin. Melanin comes in two types: phaeomelanin (red to yellow) and eumelanin (dark brown to black). People with light complexioned skin mostly produce pheomelanin, while those with dark colored skin mostly produce eumelanin. In addition, individuals differ in the number and size of melanin particles.The characteristic phenotype of fair skin, freckling, and carrot-red hair is associated with large amounts of pheomelanin and small amounts of eumelanin.
Studies suggest that both amount and type are determined by over 10 genesand several SNPs*, which operate under incomplete dominance. One copy of each of those genes is inherited from the father and one from the mother. Each gene may have several possible alleles. Therefore, a great variety of different skin colorswill result.
Other factors involved include: 1) Some people have almost colorless skin and, therefore, red cells in blood flowing close to the skin affect the color, 2) Hormones may also affect skin color particularly during pregnancy and in birth control pills, 3) To a lesser extent, the color is affected by the presence of fat under the skin and carotene, a reddish-orange pigment in the skin. Skin color is a complicated trait and there are many other factors involved.
Advantages of Dark Skin.
Skin pigment protects against UV,so protects againstthe aging of the skin- wrinkling and ‘age’ spots. Melanin also helps prevent sunburn damage and,skin cancer.In the United States, approximately 44,200 people get the most severe form of skin cancer, melanoma, every year, and about 7,300 of them will eventually die from it. Those at highest risk are European Americans.In Australia, the lifetime cumulative incidence of skin cancer approaches 50%
Tanning is primarily an increase in the number and size of melanin granules due to stimulation by ultraviolet exposure. Some light skinned northwest Europeans have lost all or most of their ability to tan (produce eumelanin).Their skin burns and peels rather than tans. They have a 10 times higher risk of melanoma than African Americans.
*This does not include several types of albinism.
Another serious effect of UV radiation is the break-down of folate, an essential vitamin B needed for cell division and producing new DNA. Pregnant women in particular require large amounts of folate to support rapid cell division in the embryo. Women of reproductive age are advised to take folate supplements to prevent serious birth defects such as spina bifida (neural tube defect).
Although not complete, the advantages of dark skin also may include an added barrier to bacterial and other microbial infections.
Advantages of lighter skin
In regions away from the equator, where UV levels are lower, humans are fairer so as to allow enough UV radiation to penetrate their skin and produce vitamin D. Vitamin D is essential for maintaining healthy calcium and phosphorous absorption, thus promoting bone growth.Calcium is also necessary in adults to maintain normal heart action, blood clotting, and a stable nervous system. In addition, a deficiency in vitamin D may result inrickets disease in children and osteoporosis in adults.Females have lighter skin than males (In general, they produce 3-4% less melanin than males). This may be due to the higher calcium needs of women during pregnancy.In addition, women who had prolonged vitamin D3deficiencies as girls have a higher incidence of pelvic deformities that prevent normal delivery of babies.
Evolutionary studies suggest that:
- From ~1.2 million years ago to less than 100,000 years ago, after the loss of most of our body hair, the ancestors of all people alive were from Africa and had dark skin.
- As populations began to migrate, the evolutionary constraint keeping skin dark decreased proportionally to the distance North a population migrated, resulting in a range of skin tones within northern populations.
- At some point northern populations experienced positive selection for lighter skin due to the increased production of vitamin D from sunlight and the genes for darker skin disappeared from these populations.
4. This may have been increased due to agriculture which altered the diet of Northern peoples, requiring them to produce more of their own vitamin D.
That is the case with Eskimos and other inhabitants of northern Alaska and northern Canada. "Looking at Alaska, one would think that the native people should be pale as ghosts." One of the reasons they're not is that their traditional diet is rich in fish and other seafood. They've consumed huge doses of vitamin D, so they haven't had to undergo the same reduction in pigmentation that would otherwise be required at such high latitudes. "What's really interesting is that if these people don't eat their aboriginal diets of fish and marine mammals, they suffer tremendously high rates of vitamin D-deficiency diseases such as rickets in children and osteoporosis in adults." A similar problem occurs when darker skinned people move to Northern latitudes. Advances in nutrition have larger overcome this problem.
Skin color basically becomes a balancing act between the demands of photo-protection and the need to create vitamin D in the skin. Therefore, ancient humans were under selective pressure for skin color in the range that would protect them against too much UV yet allow enough in to create vitamin D.
Populations with similar pigmentation may be genetically no more similar than other widely separated groups.
2. Does skin color follow the rulesfor biological classification?
B. Traditional racial classifications use more than one trait:
C. Unclassifiable groups
D. If traits used for the traditional racial classifications aren’t tightly defined, then which traits should be chosen to classify humans? Some possibilities follow:
1. Traits of medical importance, such as resistance to certain diseases?
2. Traits with nutritional importance, such as lactose intolerance?
3. Other physical traits, such as fingerprint patterns?
1. Traits of medical importance, such as resistance to certain diseases
Example:
If we use malaria resistance as our defining characteristic, our races would look like this:
RaceIncludes people from:
Malaria-resistant race:Tropical Africa
Southern India
Arabian Peninsula
Southeast Asia
New Guinea
Mediterranean basin
Malaria-nonresistant race:Northern Europe
Southernmost Africa
2. Traits of nutritional importance?
Example: Lactase production in adulthood.
RaceIncludes people from:
Lactase-positive race:Northern & Central Europe
Arabians
Northern Indians
West Africa
Lactase-negative race:Southern Europe
East Asians
Aboriginal Australians
American Indians
3. Or we can use other physical traits. Example: Fingerprint patterns.
RaceIncludes people from:
Looped race:Europeans
Africans
East Asians
Whorled race: Mongolians
Aboriginal Australians
Arched race: Khoisan Africans
Central Europeans
E. So what’s wrong with humans?! Why is it so difficult to form scientifically valid ‘races’ in humans compared to many other organisms?
1. Human populations have always interbred. Gene exchange has always occurred.
a. Interbreeding between neighboring populations.
b. Migration to distant populations.
2. Even secluded groups have not been isolated long enough to disconnect their genetics from other populations. Not enough genetic change has occurred to create ‘races’.
F. So why are the traditional human racial groupings used?
1.
2.
3. What does separate us?
“Traditional ‘racial’ designations in humans are not bounded, discrete categories but are fluid, socially defined constructs that have some poorly understood correlations with various biological elements and health outcomes.”
IV. Human Genome Project
The Human Genome Project seeks to find variation (differences) between people without value judgments of individual or group worth. There are many worthwhile reasons for finding these variations.
A. One of the main goals of the HGP is to benefit humans medically. A helpful discovery has been that different people have altered responses to drugs due to genetic variations.
Pharmacogenomics
B. Concerns about the Human Genome Project
1. Exploitation of third world peoples.
a. Profits
b. Patents
c. Informed consent
2. Using genetics to devalue specific races.
Example: Hypertension study: Randall Tackett (U. of Georgia)
a. Results: Black men’s veins don’t return to normal as quickly after being exposed to chemicals that cause them to constrict.
“This is the first direct demonstration that there are racial differences at the level of the vasculature.”
b. What didn’t he emphasize?
1) Only 22 men from Georgia were tested.
2) Native Africans have very low rates of hypertension.
3) Finns and Russians have notoriously high rates of hypertension.
“What you make of race depends on what the question is. And who wants to know.”
(Shreeve, 1994).
Lecture Summary
1. Humans are difficult to classify beyond the species level.
a. Although people do differ, human groups do not differ enough genetically to form ‘races’. Races do not biologically exist in humans.
1) Human populations have always interbred.
2) Thus, there are individuals in every traditional human race with ‘alleles’ found in other traditional racial groups.
3) Our separations haven’t been long enough to form subspecies.
b. Genetically, variations among groups are better considered in dynamic populations (groups of individuals living in the same area or with common ancestry), not large groupings of people bundled into a few ‘races’.
2. Traditional racial groupings primarily are based on ‘appearance’. Appearance-based characteristics in humans are 1) not tightly defined, 2) geographically, often are found on a continuum, 3) are not easily used, and 4) using these characteristics many people are unclassifiable. Therefore, traditional racial groupings are not biologically valid.
3. Traditional racial groupings are highly subjective. Therefore, they are open to bias and value judgments of individual and group worth. This provides an excuse to devalue certain cultures, religions, ethnicities, and other groups. Appearance-based traits have not been linked to other traits such as intelligence, creativity, and athletic performance.
4. The Human Genome Project seeks to find variation (differences) between people without value judgments. However, the project leaders realize the potential problems. Three to five percent of the HGP budget has gone toward education and outreach.
5. The NHGC(National Human Genome Center)is located at Howard University.
NHGC Goal:
The goal of the NHGC is to bring multicultural perspectives and resources to an understanding of human genome variation and its implications for disease prevention and health promotion.
Primary Works Consulted for this Lecture Topic
Royal, C. and Dunston, G.M. 2004. Nature Genetics.
Lewis, R. Feb. 18, 2002. Race and the Clinic: Good Science? The Scientist.
Marks, J. Dec. 1994. Black White Other. Natural History, pp. 32-35.
Shreeve, J. Nov. 1994. Terms of Estrangement. Discover, pp. 56-63.
RACE The Power of an Illusion
Skin Color
Shades of Brown: The Law of Skin Color:
Ethnicity, Race, Racism
V. PBS The Power of an Illusion website
A. Sorting People (in-class)
There’s less—and more—to race than meets the eye.
1. Begin Sorting: Who goes where?
2. Explore Traits
3. Click on Human Diversity and take the Human Diversity Quiz
4. Click on What is Race and read 1-10
B. RACE The Power of an Illusion (Episode 1 The Difference Between Us)
Students: Read the following before the viewing RACE The Power of an Illusion (Episode 1 The Difference Between Us).
Dear Viewer,
Race is one topic where we all think we’re experts. Yet ask 10 people to define race or name "the races," and you’re likely to get 10 different answers. Few issues are characterized by more contradictory assumptions and myths, each voiced with absolute certainty.
In producing this series, we felt it was important to go back to first principles and ask, Whatis this thing called "race"? - a question so basic it is rarely raised. What we discovered is
that most of our common assumptions about race – for instance, that the world’s people
can be divided biologically along racial lines – are wrong. Yet the consequences of racism
are very real.
How do we make sense of these two seeming contradictions? Our hope is that this series can help us all navigate through our myths and misconceptions, and scrutinize some of
the assumptions we take for granted. In that sense, the real subject of the film is not so
much race but the viewer, or more precisely, the notions about race we all hold.
—Larry Adelman, Executive Producer
PRINT The Power of An Illusion DVD questions ON THE LAST PAGE OF THIS DOCUMENT.While/after viewing the DVD, answer the questions on the last page of this document.
RACE and GENETICS
Post-Test
1. List the classification hierarchy taxa in the correct order.
2. What are some of the characteristics of all members of the species Homo sapiens?
3. What is the basis for classifying sexually reproducing organisms into the same species?
4. Describe the ‘subjective’ nature of scientific classification (for any organism).
5. Explain how populations of organisms (any species) accumulate differences over time.
6. Who was the first person to classify humans into four primary varieties? What were these varieties?
7. Describe Blumenbach’s classification system of humans. What effect did his classification have on human societies? Why?
8. In order to be scientifically valid, a subspecies classification must follow what ‘rules’?
9. Why can’t these ‘rules’ be followed with respect to human racial classification? In other words, why is it so difficult to classify humans beyond the species level?
10. What types of characteristics have been used for traditional racial groupings?
11. Describe the biology and inheritance of skin color. Include advantages of dark and light skin in high UV and low UV environments, respectively.
12. Why is skin color (or any appearance-based characteristic) a bad choice for grouping humans? Why have appearance-based characteristics been used by humans for ‘racial’ classifications?
13. Why don’t resistance to disease, lactose intolerance and fingerprint patterns form tightly defined groups of humans?
14. Give an example of an ‘unclassifiable’ group of people, and describe why this group is unclassifiable based on traditional racial groupings.
15. What does separate the ‘races’?
16. How do geneticists prefer to study humans? Why?
17. Give an example of how the human genome project has been used to provide medical information.
18. Describe concerns associated with the Human Genome Project.
19. From a biological perspective, are human ‘races’ meaningful and useful? Why or why not.