[Original publication date: Nov. 16, 2011]
In response to my Ask a Nerd post, Lucia asked:
I have a science question that is very unpopular. I do not mean to be offensive, I really do want a good scientific answer to understand these ideas. So, here goes”:
Is there a genetic basis for racial differences? I am a social scientist by training (and a person of color) and frequently hear/read that “race is socially constructed.” I understand the socially defined aspect to racial concepts. But I also know that Latinos have higher rates of diabetes, African Americans sickle cell, Tay-Sachs among the Jewish population and so on. Furthermore, the bone marrow and organ donor registries have clear campaigns targeted at minority populations that say matches are more likely within one’s ethnic and racial group.
So, is there a biological, genetic or some other scientific definition of race that renders “race is socially constructed” false? Thanks very very much.
Short answer: No, there is no genetic basis for race that negates the social construct.
On Anthropology.net, Emanuel Lusca writes:
First, race is a social construct contingent on collective acceptance, agreement, and imposition. Second, race has always been defined by the dominant group in society. Third, race indicates differences in status. The status indicated by which race you are, either includes or excludes one from broader social constructs, and disables or enables certain powers.
To understand the connection between race and genes, we first need to review some basics of genetics. With the exception of individuals with certain genetic disorders, humans have 46 paired chromosomes, 23 from each parent. During meiosis, the genes recombine so that each sperm or ovary contains a mix of genes from each copy of the chromosome. Mutations arise fairly frequently, but only survive if they are not detrimental to the survival of their host. If a mutation provides a reproductive advantage to its host, over many generations it can become widespread. Even neutral mutations can spread if they confer no disadvantage (or if only one copy is not disadvantageous), especially in isolated groups. If a group is reproductively isolated, either geographically or culturally, a particular version of a gene can become very common in that group even if it is not present in others.
Tay-Sachs disease and Sickle-Cell disease, along with many other inherited conditions, are autosomal recessive genetic disorders. This means the affected gene is not located on the sex chromosome and an individual must inherit a copy of the defective gene from both parents to show symptoms. An individual with one copy of the gene is known as a carrier. If a carrier reproduces with a non-carrier, theres a 50/50 chance that each of their offspring will also be a carrier, but they will not be symptomatic. If two carriers reproduce, there’s a 50% chance each child will be a carrier, a 25% chance the child will inherit two “good” copies of the gene and will be unable to pass it on to future generations, and a 25% chance the child will get a mutated gene from both parents and be afflicted with the related disorder.
Tay-Sachs disease is commonly associated with Ashkenazi Jews but can occur in people of any racial or ethnic background. The condition is caused by a mutation of a specific gene on chromosome 15 that causes premature cell death in the nerve cells of the brain, and it is nearly always fatal at a very young age. One specific mutation is common among Ashkenazi Jews and Cajuns in Louisiana; another among French-Canadians in Quebec. Still more mutant forms of the gene occur rarely but are not linked with any particular group, and it is possible to develop the disease by inheriting two different mutations. There is nothing inherently “Jewish” about Tay-Sachs disease; historically the Ashkenazi population has been reproductively isolated for cultural and religious reasons and therefore that particular mutant gene has had little opportunity to spread to the larger population (many of the Cajun families who carry the same gene have been traced back to a single 18th century French family; it is unknown if they had a Jewish ancestor). Until genetic testing proved that these populations carry different forms of the gene, it was widely believed that the French Canadian carriers were all descended from a single unknown Jewish ancestor who introduced it there. The disease is highly associated with Ashkenazi Jews because it’s most efficient to screen known at-risk populations, and because they have done so with great success. In 2003, only 10 North American babies were born with Tay-Sachs, and none was of Jewish heritage. Therefore, Tay-Sachs is not a reliable indicator of one’s Jewishness.
Sickle-cell disease occurs mostly in populations whose ancestors came from tropical climates with endemic malaria. Possessing a single copy of the mutated gene is advantageous because it enables individuals to better fight off this infection, but when a child inherits two copies of the mutant gene, their red blood cells form incorrectly, leading to pain, anemia, and possibly death. Mutations of this gene are widespread among individuals of sub-Saharan African, Indian, and Middle Eastern descent because their resistant ancestors were more likely to survive to reproductive age and bear children. In the U.S. it’s thought of as an African-American disease because that population is much larger than the Indian-American or Middle Eastern-American populations. The disease is actually much less common in the United States than in Africa, partly due to our lack of malarial infections to concentrate it in the survivors, and partly due to the fact that many African-Americans have some white ancestry as well and that lowers the likelihood that any individual will be a carrier.
I was unable to find any information about the genetic aspect of higher diabetes rates among Latinos (which, along with Ashkenzi Jews, is actually an ethnic group, not a race). There are definite social factors that lead to higher rates, however. A 2003 report from the UCLA Center for Health Policy Research based on 2001 diabetes rates among Latinos in California states:
…barriers such as language, non-citizen status, and low income result in decreased access to health insurance and health care services for Latino adults. Among Latinos with diabetes, nearly one out of three is primarily a Spanish speaker (31.3%), more than one out of three are non-citizens (39.7%), and nearly three out of four (68.6%) have incomes below 200% of the Federal Poverty Level (FPL).
When people have no or limited access to preventative care, whether due to lack of insurance, financial constraints, language barriers, or fear of deportation, their overall health suffers and diabetes is just one example. While there may be a genetic reason for Latinos to develop diabetes at higher rates than white, external factors must also be considered, and education about warning signs may lead to prevention and better management of the disease.
Concerning pushes for minority blood and organ donors, different blood types are more common among different populations, but none is exclusive to any one group. We are most familiar with the 8 major blood types (A+, A-, B+, B-, AB+, AB-, O+, and O-), which are based on the presence or absence of particular antibodies and antigens, but when you take into account other protein variations there are actually 30 different variables that determine precise blood chemistry. In most cases, transfusions across blood type cause an immune response, but type O- can be given to anyone, and people with AB+ blood can receive any type of blood. Organ transplants need to take into account the other protein variations to limit the chance of rejection. People are most likely to match with a blood relation due to their shared genes, and if that isn’t possible, someone with a similar heritage is more likely to match since they come from a shared gene pool. There are campaigns in place to increase awareness of organ donation because most donors in the U.S. are white, and this makes it harder for members other groups to get the transplants they need. For example, a 1998 factsheet from the Health and Human Services department states that “Twelve percent of all deceased donors [were] Blacks, but 27 percent of those on the organ transplant waiting list [were] Black.” In order to better serve non-white patients, more non-white donors are needed.
There is no gene that defines race. By and large, race is assigned to an individual based on their skin color, and there is no single skin color gene. (If there were, it would be a hell of a lot easier to buy foundation!) There are several genes that affect melanin production, and each has multiple alleles (variations). Additionally, there are two forms of melanin, pheomelanin, which is red, and eumelanin, which is very dark brown. Different versions of the genes are more predominant in different groups, and historically were beneficial in protecting from skin cancer, frostbite, and many other factors based on geographic location of one’s ancestors. Mixed race individuals tend to have darker skin than their lighter-skinned parent, since a gene that tells the body, “make lots of melanin,” is going to be expressed over one that says, “make a little bit.” However, in about 1 in 500 sets of fraternal twins born to mixed-race couples, one twin will have light skin and the other will have dark skin. To an outside observer, one will look white and the other, black, despite their identical heritage.
Also, most definitions of race use very broad strokes. The U.S. Census only recognizes five racial categories: American Indian or Alaska Native, Asian, Black or African American, Native Hawaiian or Other Pacific Islander, and White (you can now select multiple options); with a separate question to ask if individuals are of Hispanic or Latino ethnicity. By this definition, an Arab is the same race as a Korean, though their heritage is vastly different. There can be no meaningful genetic reason behind this; the definition is purely socio-geographic. Practically speaking, a light-skinned person of African descent might “pass” for white, while Australian Aboriginals would appear “black” to many people based solely on skin color, despite being much more distantly related to Africans than most Europeans are. White people love to break down their ancestry in precise fractions (1/2 Italian, 1/4 Puerto Rican, 1/32 Cherokee, etc) and celebrate this heritage with parades, but rarely recognize the differences between different groups within other races. They are, simply, “other.”
In conclusion, there are some genetic differences between members of different races or ethnic groups, but this doesn’t make the groups fundamentally different and has almost nothing to do with how race is addressed in society today. Our melanin levels, genetic mutations, and blood proteins have absolutely nothing to do with how we exist as individuals and interact with each other unless you account for social constructs of race.