Genetics

Conclusions

Data from many sources have shown that humans are genetically homogeneous and that genetic variation tends to be shared widely among populations. Genetic variation is geographically structured, as expected from the partial isolation of human populations during much of their history. Because traditional concepts of race are in turn correlated with geography, it is inaccurate to state that race is "biologically meaningless." On the other hand, because they have been only partially isolated, human populations are seldom demarcated by precise genetic boundaries. Substantial overlap can therefore occur between populations, invalidating the concept that populations (or races) are discrete types.

When large numbers of loci are evaluated, it is often possible to infer individual ancestry, at least approximately. If done accurately and with appropriate reservations, ancestral inference may be useful in genealogical studies, in the forensic arena and in the design of case-control studies. This should not be confused, however, with the use of ethnicity or race (genetically measured or self-identified) to make decisions about drug treatment or other medical therapies. Responses to these therapies will often involve nongenetic factors and multiple alleles, and different populations will often share these alleles. When it finally becomes feasible and available, individual genetic assessment of relevant genes will probably prove more useful than race in medical decision making.

In the meantime, ethnicity or race may in some cases provide useful information in biomedical contexts, just as other categories, such as gender or age, do. But the potential usefulness of race must be balanced against potential hazards. Ignorance of the shared nature of population variation can lead to diagnostic errors (e.g., the failure to diagnose sickle-cell disease in a European individual or cystic fibrosis in an Asian individual) or to inappropriate treatment or drug prescription. The general public, including policy-makers, are easily seduced by typological thinking, and so they must be made aware of the genetic data that help to prove it wrong.

A particular area of concern is in the genetics of human behavior. As genes that may influence behavior are identified, allele frequencies are often compared in populations67, 68. These comparisons can produce useful evolutionary insights but can also lead to simplistic interpretations that may reinforce unfounded stereotypes69. In assessing the role of genes in population differences in behavior (real or imagined), several simple facts must be brought to the fore. Human behavior is complicated, and it is strongly influenced by nongenetic factors70. Thousands of pleiotropic genes are thought to influence behavior, and their products interact in complex and unpredictable ways. Considering this extraordinary complexity, the idea that variation in the frequency of a single allele could explain substantial population differences in behavior would be amusing if it were not so dangerous.

Race remains an inflammatory issue, both socially and scientifically. Fortunately, modern human genetics can deliver the salutary message that human populations share most of their genetic variation and that there is no scientific support for the concept that human populations are discrete, nonoverlapping entities. Furthermore, by offering the means to assess disease-related variation at the individual level, new genetic technologies may eventually render race largely irrelevant in the clinical setting. Thus, genetics can and should be an important tool in helping to both illuminate and defuse the race issue.

Posted By: JD3, Oct 31, 17:06:29