What is race?

Conflicting Definitions of Race

Few ideas have had such a contentious history as the use of the term “race.” Categorization relied on consideration of salient traits such as skin color, body form and hair texture to classify humans into distinct subcategories. The term “race” is currently believed to have little biological meaning, in great part because of advances in genetic research. Studies have revealed that a person’s genes cannot define their ethnic heritage and that no gene exists exclusively within one race/ethnocultural group. Biomedical scientists remain divided on their opinion about “race” and how it may be used in treating human genetic conditions.

For a racial or subspecies classification scheme to be objective and biologically meaningful, researchers must decide carefully which heritable characteristics (passed to future generations genetically) will define the groups. Several principles are considered. First, the unique traits must be discrete and not continually changing by small degrees between populations. Second, everyone placed within a specific race must possess the selected trait’s defining variant. All the selected characteristics are found consistently in each member of the group. For example, if blue eyes and brown hair are chosen as defining characteristics, everyone designated as belonging to that race must share both of those characteristics. Individuals placed in other races should not exhibit this particular combination. Third, individuals of the same race must have descended from a common ancestor, unique to those people. Many shared characteristics present in individuals of a race may be traced to that ancestor by heredity. Based on the preceding defining criteria (selection of discrete traits, agreement of traits, and common ancestry), pure representatives of each racial
category should be detectable.

Most researchers maintain that traditional races do not conform to scientific principles of subspecies classification. For example, the traits used to define traditional human races are rarely discrete. Skin color, a prominent characteristic employed, is not a well-defined trait. Approximately eleven genes influence skin color significantly, but fifty or so are likely to contribute. Pigmentation in humans results from a complex series of biochemical pathways regulated by amounts of enzymes (molecules that control chemical reactions) and enzyme inhibitors, along with environmental factors. Moreover, the number of melanocytes (cells that produce melanin) do not differ from one person to another, while their level of melanin production does. Like most complex traits involving many genes, human skin color varies on a continuous gradation. From lightest to darkest, all intermediate pigmentations are represented. Color may vary widely even within the same family. The boundary between black and white is an arbitrary, humanmade border, not one imposed by nature.

In addition, traditional defining racial characteristics, such as skin color and facial characteristics, are not found in all members of a race. For example, many Melanesians, indigenous to Pacific islands, have pigmentation as dark as any human but are not classified as “black.” Another example is found in individuals of the Cherokee Nation that have Caucasoid facial features and very dark skin, yet have no European ancestry. When traditional racial characteristics are examined closely, many groups are left with no conventional racial group. No “pure” genetic representatives of any traditional race exist.

Common ancestry must also be considered. Genetic studies have shown that Africans do not belong to a single “black” heritage. In fact, several lineages are found in Africa. An even greater variance is found in African Americans. Besides a diverse African ancestry, on average 13 percent of African American ancestry is Northern European. Yet all black Americans are consolidated into one race.

The true diversity found in humans is not patterned according to accepted standards of a subspecies. Only at extreme geographical distances are notable differences found. Human populations in close proximity have more genetic similarities than distant populations. Well-defined genetic borders between human populations are not observed, and racial boundaries in classification schemes are most often formed arbitrarily.

History of Racial Classifications

Efforts to classify humans into a number of distinct types date back at least to the 19th Dynasty of Ancient Egypt. The sacred text Book of Gates described four distinct groups: “Egyptians,” “Asiatics,” “Libyans,” and “Nubians” were defined using both physical and geographical characteristics. Applying scientific principles to divide people into distinct racial groups has been a goal for much of human history.

In 1758, the founder of biological classification, Swedish botanist Carolus Linnaeus, arranged humans into four principal races: Americanus, Europeus, Asiaticus, and Afer. Although geographic location was his primary organizing factor, Linnaeus also described the races according to subjective traits such as temperament. Despite his use of archaic criteria, Linnaeus did not give superior status to any of the races.

Johann Friedrich Blumenbach, a German naturalist and admirer of Linnaeus, developed a classification with lasting influence. Blumenbach maintained that the original forms, which he named “Caucasian,” were those primarily of European ancestry. His final classification, published in 1795, consisted of five races: Caucasian, Malay, Ethiopian, American, and Mongolian. The fifth race, the Malay, was added to Linnaeus’s classification to show a step-by-step change from the original body type.

After Linnaeus and Blumenbach, many variations of their categories were formulated, chiefly by biologists and anthropologists. Classification “lumpers” combined people into only a few races (for example, black, white, and Asian). “Splitters” separated the traditional groups into many different races. One classification scheme divided all Europeans into Alpine, Nordic, and Mediterranean races. Others split Europeans into ten different races. No one scheme of racial classification came to be accepted throughout the scientific community.

Genetics and Theories of Human Evolution

Advances in DNA technology have greatly aided researchers in their quest to reconstruct the history of Homo sapiens and its diversification. Analysis of human DNA has been performed on both nuclear and mitochondrial DNA. The nucleus is the organelle that contains the majority of the cell’s genetic material. Mitochondria are organelles responsible for generating cellular energy. Each mitochondrion contains a single, circular DNA molecule. Research suggests that Africa was the root of all humankind and that humans first arose there 100,000 to 200,000 years ago. Several lines of research, including DNA analysis of humanoid fossils, provide further evidence for this theory.

Many scientists are using genetic markers to decipher the migrations that fashioned past and present human populations. For example, DNA comparisons revealed three Native American lineages. Some scientists believe one migration crossed the Bering Strait, most likely from Mongolia. Another theory states that three separate Asian migrations occurred, each bringing a different lineage.

Genetic Diversity Among Races

Three primary forces produce the genetic components of a population: natural selection, nonadaptive genetic change, and mating between neighboring populations. The first two factors may result in differences between populations, and reproductive isolation, either voluntary or because of geographic isolation, perpetuates the distinctions. Natural selection refers to the persistence of genetic traits favorable in a specific environment. For example, a widely held assumption concerns skin color,
primarily a result of the pigment melanin. Melanin offers some shielding from ultraviolet solar rays. According to this theory, people living in regions with concentrated ultraviolet exposure have increased melanin synthesis and, therefore, dark skin color conferring protection against skin cancer. Individuals with genes for increased melanin have enhanced survival rates
and reproductive opportunities. The reproductive opportunities produce offspring that inherit those same genes for increased melanin. This process results in a higher percentage of the population with elevated melanin production genes. Therefore, genes coding for melanin production are favorable and persist in these environments.

The second factor contributing to the genetic makeup of a population is nonadaptive genetic change. This process involves random genetic mutations (alterations). For example, certain genes are responsible for eye color. Individuals contain alternate forms of these genes, or alleles, which result in different eye color. Because these traits are impartial to environmental influences, they may endure from generation to generation. Different populations will spontaneously produce, sustain, and delete them.

The third factor, mating between individuals from neighboring groups, tends to merge traits from several populations. This genetic mixing often results in offspring with blended characteristics.

Several studies have compared the overall genetic complement of various human populations. On average, any two people of the same or a different race diverge genetically by a mere 0.1 percent. It is estimated that only 0.012 percent contributes to traditional racial variations. Hence, most of the genetic differences found between a person of African descent and a person of European descent are also different between two individuals with the same ancestry. The genes do not differ. It is the proportion of individuals expressing a specific allele that varies from population to population.

Upon closer examination, it was found that the continent of Africa is unequaled with respect to cumulative genetic diversity. Numerous races are found in Africa, Khoisan Africans of southern Africa being the most distinct. Therefore two people of different ethnicities who do not have recent African ancestry (for example Northern Europeans and South East Asians) have more similar genetics than any two distinct African ethnic groups. This finding supports theories of early human migration in which humans first evolved in Africa and a subset left the continent, experienced a population bottleneck, and then established the human populations around the world.

Human Genome Diversity Project and Advances in Research

Many scientists are attempting to reconcile the negativities associated with racial studies. The Human Genome Diversity Project (HGDP), was initiated by Stanford University in 1993 and functions independently from the Human Genome Project. The HGDP aims to collect and store DNA from ethnically diverse populations around the world, creating a library of samples to represent global human diversity. Results of future studies may aid in gene therapy treatments and greater success with organ transplantation. As a result, a more thorough understanding of the genetic diversity and unity in the species Homo sapiens will be possible.

At the population level, human diversity is greatest within racial/cultural groups rather than between them. Originally, geneticists who studied genetic diversity of human populations were limited to data from very few genetic loci (locations in the genome that are of interest); however, recent studies are able to simultaneously analyze hundreds to thousands of loci. It is currently estimated that 90 percent of genetic variation in human beings is found within each purported racial group, while differences between the groups only equate to the remaining 10 percent.

A second method of studying human genetic diversity is to compare ethnically diverse individuals and search for similarities and differences in their genomes. Early studies involved only a few dozen genetic loci and as a result did not find individuals to cluster (group together) based on their geographic origin. Recent studies, however, were able to analyze substantially more genetic loci and resulted in data with stronger statistical power. These studies focused on individuals from three distinct geographic areas: Europe, sub-Sahran Africa, and East Asia. Indeed, individuals clustered or shared more genetic similarities with others of the same geographic region. Participants from Africa were found to have the greatest diversity, which is in agreement with population studies. Another cluster consisted exclusively of Europeans, and a third comprised the Asian individuals. However, when individuals from neighboring regions were also analyzed, such as South Indians, the analysis showed similarities to both East Asians and Europeans. This finding may be explained by the numerous migrations between Europe and India during the past ten thousand years.
Many individuals did not cluster with their geographic cohorts, demonstrating that individuals are not easily categorizeable into neat groups of races but tend to share more genetic similarities with people from their region.

Race or an individual’s ancestry can sometimes provide useful information in medical decision making, as gender or age often do. Certain genetic conditions are more common among ethnocultural groups. For example, hemochromatosis is more prevalent within Northern Europeans and Caucasians, whereas sickle-cell disease is more often found in Africans and African Americans. Meanwhile other genetic diseases are equally prevalent across racial groups, as seen in spinal muscular atrophy (SMA). If a disease-causing gene is common, then it is likely to be relatively ancient and thus shared across ethnicities. Moreover, some genetic conditions remain prevalent in populations because they provide an adaptive advantage to the individual, as seen in sickle-cell disease carriers being protected against malarial infection. Likewise, an individual’s response to drugs may be mediated by their genetic makeup. A gene called
CYP2D6
is involved in the metabolism or breakdown of many important drugs such as codeine and morphine. Some individuals have no working copy of this gene whereas others have one or two copies that function properly. The majority of individuals with no working copies are of European heritage (26 percent), whereas fewer Asian (6 percent) and African populations (7 percent) fall into this category. Thus it may be tempting to make medical decisions based on a patient’s ethnic heritage; however, this may lead to inaccurate diagnoses (missing sickle-cell disease in an Asian individual) or inappropriate drug administration (prohibiting a Caucasian person from taking codeine). Ideally, each individual should have medical decisions made based on their genetic makeup in lieu of their ethnic heritage. Future patients may be able to first request an analysis of their genome, which would aid their physicians in making some genetically appropriate medical
decisions.

Sociopolitical Implications

Race is often portrayed as a natural, biological division, the result of geographic isolation and adaptation to local environment. However, confusion between biological and cultural classification obscures perceptions of race. When individuals describe themselves as “black,” “white,” or “Hispanic,” for example, they are usually describing cultural heredity as well as biological similarities. The relative importance of perceived cultural affiliations or genetics varies depending on the circumstances. Examples illustrating the ambiguities are abundant. Nearly all people with African American ancestry are labeled black, even if they have a white parent. In addition, dark skin color designates one as belonging to the black race, including Africans and aboriginal Australians, who have no common genetic lineage. State laws, some on the books until the late 1960’s, required a “Negro” designation for anyone with one-eighth black heritage (one black great-grandparent).

Unlike biological boundaries, cultural boundaries are sharp, repeatedly motivating discrimination, genocide, and war. In the early and mid-twentieth century, the eugenics movement, advocating the genetic improvement of the human species, translated into laws against interracial marriage, sterilization programs, and mass murder. Harmful effects include accusations of deficiencies in intelligence or moral character based on traditional racial classification.

The frequent use of biology to devalue certain races and excuse bigotry has profound implications for individuals and society. Blumenbach selected Caucasians (who inhabit regions near the Caucasus Mountains, a Russian and Georgian mountain range) as the original form of humans because in his opinion they were the most beautiful. All other races deviated from this ideal and were, therefore, less beautiful. Despite Blumenbach’s efforts not to demean other groups based on intelligence or moral character, the act of ranking in any form left an ill-fated legacy.

In conclusion, race remains a contentious issue both in many fields of science and within the greater society. Recent genomic studies at both the individual and the population level have shown that the majority of human genetic composition is universal and shared across all ethnocultural groups. Shared genetics is most commonly found in individuals who originate from the same geographic region. However, there is no scientific support for the concept of distinct, “pure,” and nonoverlapping races. Unfortunately throughout human history, the use and abuse of the term “race” has been pursued for sociopolitical gains or to justify bigotry toward and abuses of individuals. It is now known that human genetic diversity is a continuum, with natural selection, nonadaptive genetic change, and mating as the true driving forces for human genetic diversity.

Key terms



eugenics

:

a movement concerned with the improvement of human genetic traits, predominantly by the regulation of mating




Human Genome Diversity Project

:

an extension of the Human Genome Project in which DNA of native people around the world is collected for study




population

:

a group of geographically localized, interbreeding individuals




race

:

a collection of geographically localized populations with well-defined genetic traits





Bibliography

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