Racehumanvariation.pptxHuman Variation - Race
Are American racial categories biologically real?
What makes humans vary?
Germline mutations, epigenetic effects, gene flow, genetic drift, and sexual recombination.
Most human traits are polygenic.
Nutrition
Environmental circumstances
Culture (education, family dynamics, wealth)
Think back to our early discussion of variation for natural selection.
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Population Studies
We compare frequencies of alleles in populations to show genetic relationships
Population genetics studies the difference in allele frequencies among populations
Evolution is occurring if frequencies of alleles change over generations = microevolution
Population genetic studies help to understand migration patterns in early human history, and more importantly, why traits begin to develop as a product of culture.
In order to measure human variation, we use population studies. In these, we compare the frequencies of certain traits in a population and then try to find out why. For instance, we’ve talked about the sickle cell trait. We’ve done many population studies to find out where this trait is most common, this is how we were able to relate it to areas where malaria is most common as well.
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Biological vs. Cultural Race
Biological race: Subspecies that have distinct gene frequencies and/or consistently identifiable characteristics.
Cultural race: The term race refers to groups of people who have differences and similarities in physical traits deemed by society to be socially significant, meaning that people treat other people differently because of them. Ours is skin color.
Human “races” are a new concept, ancient societies used religion and wealth as means of identification.
Slavery predates racial categories.
Racial categories developed out of slavery as justification to prevent freedom.
Race can then be used to justify inequality through biological determinism.
Biological determinism leads to eugenics and social darwinism.
Race is a concept that is controversial among anthropologists. In general, we do not believe it exists in our species biologically. However, race does exist in other species. Consider dog breeds. Dog breeds have distinct traits that, in whole, make that dog unique. If you think of a chihuahua, I imagine you have a distinct image in your head with just minor variation. Humans don’t have this, and this lecture will discuss the evidence for why not.
http://www.pbs.org/race/001_WhatIsRace/001_00-home.htm
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“Why Genes Don’t Count…”
“The concept of race is based on the idea of fixed, ideal, and unchanging types. Race was first a European folk concept from an era in which the world was seen as fixed and unchanging…”
But things are changing! So does the concept of race depending on era and location.
Please consider this interview with Alan Goodman, an evolutionary biologist, and an expert in why humans do not have distinct races. http://www.pbs.org/race/000_About/002_04-background-01-07.htm
According to his and other’s research, races in our species are not real. One reason is that race, as Europeans new it at the time, was an unchanging ideal. Remember, they believed in the fixity of species. However, races/breeds/subspecies change over time. In fact, the cultural categories for race in our species change so often and cross culturally.
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Human Variation is Continuous
“Allele frequencies vary gradually. Therefore there is no clear place to designate where one race begins and another ends.”
Consider skin color…our primary determinant of race in this country.
Another reason that race cannot exist in our species is that the traits associated with it are polygenic, continuous traits. Skin color is the primary method for identifying races in our species and yet, skin color is a continuous and random trait determined by many genes as well as your environment. For races to exist, there has to be a set series of traits. There is no way to identify someone’s race by their skin color. Consider the next slide:
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What makes skin color a continuous trait?
Where do you stop being white and start being Hispanic? If this were a chart of hair color for dogs, you would be able to identify distinct colors unique to a dog. For instance, Weimerreiners are one of the only dogs that are silver. For us, we cannot do it. There no measurable scale of skin color to race and thus, it’s not a racial trait.
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Skin Color
Skin color is polygenic, meaning multiple influences of genes and environment.
The color of your skin is a combination of melanin, number of melanocytes, and which of the two types of melanin, eumelanin (brown, black) and pheomelanin (red, yellow) you have.
Skin color genes:
MCR1 converts pheomelanin to eumelanin…
unless it malfunctions.
Kitlg helps melanoctyes to survive, when it
malfunctions = cell death
So how is skin color determined? Please read “Skin Deep” article for this lecture. The above slide shows you at least three items involved in skin color:
Melanocytes: These are cells that produce melanin. The more you have and the more melanin they produce, the darker your skin.
Melanin: Melanin is the pigment that darkens you skin, hair, etc. The more you have, the darker that object will be.
Eumelanin versus pheomelanin: The color of melanin of courses influences the color of your skin.
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Why evolve different skin colors?
Protection from the sun
Protection of folate B, necessary for cell division.
Regulates absorption of vitamin D.
Jablonski in her TEDtalk and reading “Skin Deep” explain why skin colors have evolved. Dark skin is a protection against UV radiation, but the primary factor that explains ALL skin tones is the regulation of vitamin D. Too little and you don’t have strong bones (notice this child with rickets above), too much and you get vitamin D poisoning. Dark and light skin regulate the amount of UV radiation so it’s just enough to produce the right about of vitamin D.
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Human Variation is Nonconcordant
“Traits tend to vary independently of other traits. Race classifications, therefore, vary by the traits used in the classifications. A classification based on sickle cell might include equatorial Africa, Greeks, & Turks…”
Another piece of evidence against race in our species is that our traits are non-concordant. In races, traits should come together in sets. In humans, they do not. You can be dark skinned with blue eyes. You can be light skinned with black, curly hair. There is no concordance.
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How race becomes biology
If there is no real biological differences between “races” in this country, how do you explain….?
“in the United States…the mortality rate is bleakest for African Americans. In 2004, the overall age adjusted death rate for black Americans was more than 30% higher than it was for white Americans.”
“In 2004, the infant mortality rate among African Americans was 2.4 times the rate of other groups compared to 2.3 in 1990.”
As a result of all this evidence, the American Anthropological Association has made a clear statement about race in humans not being biological. http://www.americananthro.org/ConnectWithAAA/Content.aspx?ItemNumber=2583
The problem is, race is such a powerful cultural and social category in our species, that the oppression and discrimination experienced because of it actually DOES cause health issues in people of certain races. This is not because they are biological prone to these issues, it’s because of the oppression experienced. This means that anthropologists cannot ignore race as something that influences human biology.
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Discrimination and Biology
“At an individual level, the experience of unfair treatment or interpersonal discrimination has a wide range of embodied consequences. …linked to elevated blood pressure, breast cancer, coronary artery calcification, body mass index, preterm birth, low birth weight, depression…”
“A recent study of birth outcomes before and after September 11, 2001, provides a dramatic example…examined birth certificate data for all California births during the 6 months after September 11th, compared to the same period 1 year earlier. The found that women with Arabic names – and only women with Arabic names, experienced a 34% increased in the likelihood of having a low birth weight infant after 9/11.”
Epigenetic effects?
Gravlee, C.C. (2009). How race becomes biology: embodiment of social inequality. American Journal of Physical Anthropology, 139:47-57.
With this in mind…
Should we discount race in the sciences?
Are there other differences?
What about racial gaps in IQ tests in the U.S.?
For a select few, those disease and life expectancy examples show that race IS real. I.Q. differences in the U.S. are similarly used by a handful of people to suggest that certain races are biologically more intelligent than others. In the film above, we explore those I.Q. gaps in the U.S. About 18 minutes in is an interview with Jay Rushton, a psychologist who believes white and east Asian people are biological smarter. Let’s try to destroy his arguments with what we’ve learned…
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