In part due to the emergence of social epidemiology in the later part of the twentieth century (Krieger, 2001), the impact of dietary habits, stress, work conditions, and other aspects of daily life on health are clearer to both professional and various publics. Part of the work in this field has pointed toward how life-long differences in living conditions might explain the bulk of the variation in health among races (see for example, Williams et al., 1997). Social class and racism, for example, are closely intertwined, and both interact to affect life courses, determining exposure to, among other things, healthy foods, pollutants, and experiences of discrimination, and rendering people differentially vulnerable to exogenous risks (Krieger, 2003).
In some sense, the lived experience hypothesis is so strong and obvious and fits the data so well that even those who strongly back genetic explanations acknowledge the importance of lived experience (Satel, 2002). Yet, for reasons noted below, the tendency is not to drop a genetic explanation entirely, but to acknowledge a role for both lived experience and raciogenetics (Satel, 2002). The problem with this compromise position is that it says little about underlying etiology. Ultimately, if one wishes to address health inequities, the relative importance of these distinct etiologic pathways must be determined. Given the ascendancy of genetics in health sciences research, it is often assumed, even in the absence of empirical evidence, that somehow genetic factors are more prominent as determinants of health than those hard-to-measure factors that derive from lifestyle or social experience.
The debate among the competing causes persists, and it is both scientific and political in the sense that each hypothesis points toward a series of actions that have political and ethical implications. In the following section, I present a number of reasons why race should not be used as shorthand for human genetic variation. If race maps poorly onto genetic variation, then the raciogenetic explanation is scientifically flawed.
Why ‘Race’ ≠ Human Genetic Variation
Race is a powerful idea and a worldview that was invented and reified to explain variation in human biology, culture, and behavior (Smedley, 1999). The underpinnings of this idea can be traced to classic Greek philosophical notions of ideal types and Christian ideas about a great chain of being. However, in the view of most historians of race and slavery, the idea of biologically based human races was itself a more recent invention (Smedley, 1999). With the development of ocean travel and international migration, human differences were magnified. Colonial factors, particularly the desire to exploit lands and people, may have also contributed to the tendency toward valueladen, racialized thinking. Starting in the eighteenth century, natural historians such as Linnaeus began to classify humans into subspecies or races. These classifications persist today.
However, we now know that the raciogenetics:
- is antithetical to the idea of evolution;
- does not fit the measurable reality of the structure of human variation;
- does not translate into a concept that is epidemiologically repeatable; and
- leads to a series of conflations that inhibit understanding of disease cause, treatment, and prevention.
The Idea Of Race Versus Evolution
Race, as noted above, is largely a socially constructed idea about how human genetic variation is structured. It is, in fact, an idea that should have been cast aside with the development of evolutionary thinking (Goodman, 1997). What is perhaps most problematic about the idea of race is that it is not a process; rather, it is cast as a thing or an end result of a process. To say that race differences exist because of race is a tautology. There are in these explanations no explicitly theorized arguments relating to the processes by which race differences came into being. Yet we know now from studies of human evolution that genetic variation arose and is a result of evolution and history. The idea of race, of stable and unchanging types, inhibits rather than advances evolutionary studies of the development of human differences.
The Structure Of Human Variation
If the idea of race – dividing humans into some three or more racial groups – approximated in a useful way the geographic structure of human variation, then one might support the notion that race is an imperfect but acceptable stand-in for human genetic variation. So framed, the association of place and genetic variation does not explain everything, but it is a sort of ‘quick and dirty’ approximation (Satel, 2002). This position may have been defensible prior to the application of modern genetics to human evolutionary studies. However, it is not defensible now for the following reasons.
Human Variation Is Continuous
Allele frequencies tend to vary gradually across human populations. Definitions of race as a discontinuous category, reflecting clear ‘breaks’ in gene frequency, are thus conceptually flawed: It is impossible to identify where one race begins and another ends. Skin color, for example, varies widely by latitude and degree of exposure to ultraviolet. Since Africa covers such a wide span of latitude, it is reasonable that African groups exhibit a wide range of skin colors that overlap tremendously with individuals from other continents.
Human Traits Vary Independently From Each Other
Traits tend to vary independently of other traits. Race categories will therefore vary by the traits used to classify. A classification based on sickle cell trait might include equatorial Africans, Greeks, and Turks, while another classification based on lactase enzyme deficiency might include eastern and southern Africans with southern Europeans, Japanese, and Native Americans. There is no possibility for consistency. As skin color is only correlated with a few other phenotypic traits such as hair and eye color, it is true to say that ‘race is only skin deep.’