Does Race Exist?
If races are defined as genetically discrete groups, no. But researchers can use some genetic information to group individuals into clusters with medical relevance.
Overview / Genetics of Race
Look around on the streets of any major city, and you will see a sampling of the outward variety of humanity: skin tones ranging from milk-white to dark brown; hair textures running the gamut from fine and stick-straight to thick and wiry. People often use physical characteristics such as these--along with area of geographic origin and shared culture--to group themselves and others into "races." But how valid is the concept of race from a biological standpoint? Do physical features reliably say anything informative about a person's genetic makeup beyond indicating that the individual has genes for blue eyes or curly hair?
The problem is hard in part because the implicit definition of what makes a person a member of a particular race differs from region to region across the globe. Someone classified as "black" in the U.S., for instance, might be considered "white" in Brazil and "colored" (a category distinguished from both "black" and "white") in South Africa.
Yet common definitions of race do sometimes work well to divide groups according to genetically determined propensities for certain diseases. Sickle cell disease is usually found among people of largely African or Mediterranean descent, for instance, whereas cystic fibrosis is far more common among those of European ancestry. In addition, although the results have been controversial, a handful of studies have suggested that African-Americans are more likely to respond poorly to some drugs for cardiac disease than are members of other groups.
Over the past few years, scientists have collected data about the genetic constitution of populations around the world in an effort to probe the link between ancestry and patterns of disease. These data are now providing answers to several highly emotional and contentious questions: Can genetic information be used to distinguish human groups having a common heritage and to assign individuals to particular ones? Do such groups correspond well to predefined descriptions now widely used to specify race? And, more practically, does dividing people by familiar racial definitions or by genetic similarities say anything useful about how members of those groups experience disease or respond to drug treatment?
INDIVIDUALS from different populations are, on average, just slightly more different from one another than are individuals from the same population.
In general, we would answer the first question yes, the second no, and offer a qualified yes to the third. Our answers rest on several generalizations about race and genetics. Some groups do differ genetically from others, but how groups are divided depends on which genes are examined; simplistically put, you might fit into one group based on your skin-color genes but another based on a different characteristic. Many studies have demonstrated that roughly 90 percent of human genetic variation occurs within a population living on a given continent, whereas about 10 percent of the variation distinguishes continental populations. In other words, individuals from different populations are, on average, just slightly more different from one another than are individuals from the same population. Human populations are very similar, but they often can be distinguished.
