Human Variation

Human variation, historically a topic of much opinion, debate, and fallacy, is ruled today by deoxyribonucleic acid (DNA) technology that was absent from early classification systems. Before the onset of European exploration in the late 15th century, it was believed that humans were descended from a single pair and should not be placed into different categories as other animals were. However, the discovery of diverse cultures on different continents prompted scientists such as Linneaus, Buffon, Blumenbach, and Cuvier to distinguish Homo sapiens by physical and cultural characteristics. Carolus Linneaus, the first of these scholars, added temper, behavior, and dress to the already traditional division of skin color. Comte de Buffon, the next scientist to describe the human “race,” did so by categorizing different peoples by their geographic location. However, Buffon did not separate people into different species as Linneaus did. In 1781, Johann Friedrich Blumenbach moved away from cultural traits altogether in his classification system and the limited set of physical characteristics he described were assumed to be finite for five varieties of people. Baron Georges Cuvier condensed these groups even further into basic “white,” “yellow,” and “black.” As one of the last classification scholars, Cuvier moved to eradicate the “Great Chain of Being,” which placed humans (unsurprisingly, Europeans)at the top of the animal hierarchy.

In the mid-19th century, scientists and anthropologists began to use a different approach to the question of human variation by quantifying observed physical characteristics. This was done through anthropometry, the measuring of the body and body parts, particularly skulls, and noting variation between supposed ethnic groups. Samuel Morton measured skulls, and his conclusions are now believed to reflect his own stereotypes about certain groups of people. The cephalic index, a construct of Anders Retzius, was also used to compare different groups of people by cranial measures, which placed them into two categories:dolichocephalic and brachycephalic. However, one of the problems with craniometric analyses is that people from extremely different geographic locales may show similarities, giving questionable basis for division.

The number of “types” of people, however, lingers in a state of disagreement over characteristics that define a “race.” Thus, there have been many different definitions of the race concept. One of the broadest and currently accepted of these definitions was suggested by Huxley and Haddon in the 1930s and is the replacement of the word race with the term ethnic groups. The most conclusive definitions emphasize that the human species is polytypic, with different features loosely corresponding to certain geographic areas. There are three main ways that these differences come about: environmental adaptations, population genetics, and migration.

First, there are adaptive environmental traits unique to certain locales. Perhaps the best documented of these is sickle-cell anemia, an inherited disease in which red blood cells that are normally disk shaped are crescent shaped. The sickle-cell gene is common in Africa because it serves a distinct selective purpose. Those who carry one copy of the gene are resistant to malaria, a mosquito-borne illness. Those who carry two copies of the gene, however, have sickle-cell disease (SCD) and rarely live to reproductive age. Because of the pressures malaria places on those who live in high-risk areas such as Africa, populations in those environments have adapted and now possess a genetic trait indicative of their ancestry.

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