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What Is the History of Human Classification?

European scholars of the 18th through early 20th centuries classified humans into a series of subspecies based on geographic location and phenotypic features such as skin color, body size, head shape, and hair texture. Some scholars went a step farther and placed these types into a hierarchical framework in which the “white” race was considered to be superior to other races. With time, these efforts to classify humans into higher and lower forms were discredited for being racist and unscientific.

Is the Biological Concept of Race Useful for Studying Physical Variation in the Human Species?

No. Biologically defined, “race” refers to subspecies, and no subspecies exist within modern Homo sapiens. The vast majority of biological variation within our species occurs within populations rather than among them. Furthermore, the differences that do exist among populations occur in gradations from one neighboring population to another without sharp breaks. For these and other reasons, anthropologists have actively worked to expose the fallacy of race as a biological concept while at the same time acknowledging the existence of race as a cultural construct.

Is Studying Differences in Intelligence among Populations Valid?

These studies are flawed in many ways. First, studies attempting to document biological differences generally involve comparisons among races—a category that for humans is biologically false. Second, intelligence is a multifaceted phenomenon, and cultures vary in terms of which aspects of intelligence they value. Third, most instruments (tests) used to measure intelligence are biased toward the dominant culture of the people who created the test. Finally, as a complex set of traits, intelligence cannot be linked to discrete evolutionary forces acting in a particular environment.

What Are the Causes of Physical Variability?

Physical variability is a product of underlying genetic variation as it is expressed in a particular environment. Some physical traits are controlled by single genes, with variation present in alternate forms of the gene (alleles). Many physical characteristics like height, weight, or skin color are controlled by multiple genes and are thus expressed continuously, meaning this variation cannot be divided into discrete categories. Because evolutionary forces such as natural selection and random drift act on each physical trait independently, human biological variation can be studied only “one trait at a time.”

From male to female, short to tall, light to dark, biological variation can be categorized in a number of ways, but in the end we are all members of the same species. Minute variations of our DNA give each of us a unique genetic fingerprint, yet this variation remains within the bounds of being genetically human. Visible differences are expressed within the framework of biological features shared throughout the species, and as a species, humans vary.

Human genetic variation generally is distributed across the globe in a continuous fashion. From a biological perspective, this variation sometimes follows a pattern imposed by interaction with the environment through the evolutionary process of natural selection. At other times, the variation results from random genetic drift. The significance we give our biological variation, however, is always patterned because the way we perceive variation—in fact, whether we perceive it at all—is determined by culture.

For example, in many Polynesian cultures, where skin color is not a determinant of social status, people pay little attention to this physical characteristic. By contrast, in countries such as the United States, Brazil, and South Africa, where skin color is a significant social and political category, it is one of the first things people notice. Furthermore, our brains appear to be hardwired for categorical thinking that, once learned, predisposes us to use these kinds of distinctions. We use different parts of our brain to think about people we consider to be like ourselves compared to the parts of the brain used when we are thinking about others. Biological diversity, therefore, cannot be studied without an awareness of the cultural dimensions that shape the questions asked about diversity as well as the history of how this knowledge has been used.

When European scholars first began their systematic study of worldwide human variation in the 18 th century, they were concerned with documenting differences among human groups. Soon afterward, some began to divide these groups hierarchically into progressively “better types” of humans. Today, this hierarchical approach has been appropriately abandoned. Before exploring how contemporary biological variation is studied, we will examine the effects of social ideas about race and racial hierarchy on the interpretation of biological variation, past and present.