Marrying Race And Ethnicity To Genetic Variation

Biologists have long tussled with the meaning of race and ethnicity. Studies of these concepts can be traced to the beginning of recorded history and numerous efforts have been made at their classification. Initially, skin color and other conspicuous differences between populations were used for this purpose, but no serious attempts at classification could be made until the eighteenth century when greater geographic knowledge of the earth became available. Then, lists of human races, or "varieties" as Linneaus called them, were made, and classification was based on anthropomorphic traits, such as the cephalic index, stature, and limb measurements. But Darwin argued it was hardly possible to accept any of these as clear-cut distinctions because they were subject to rapid changes induced by the environment, and graduated into each other.3

As modern humans (Homo sapiens) spread around the world, naturalists were prompted to classify them into three groups, Negroids, Mongoloids, and Caus-casoids. But this classification has not always been applied consistently because two smaller groups, the Capoids (Bushmen and Hottentots) and Australoids, are sometimes added to these three major races, and as recent as the year 2000, five major groups--black or African-American, white, Asian, native Hawaiian or other Pacific Islander, and American Indian or Alaska native—were used in the U.S. census for that year.4 Broadly speaking, four descriptive criteria have been used to specify races: (1) geographic, which is founded on the idea that the exchange of genes is reduced as the distance between populations increases (until 150 years ago, most movements covered distances of no more than 150 miles and only rarely did people venture beyond this short range); (2) anthropologic, which focuses on similarity of height, weight, body build, and facial features as traits that could be easily perceived; (3) linguistic, which takes account of the relationships between 4736 languages of the world (interestingly the evolution of linguistic and genetic trees tend to parallel each other); and (4) ethnic, which attempts to take account of social, behavioral, and cultural characteristics. Historically, geography appears to be the greatest force affecting genetic differentiation among humans, and the order of importance of these criteria for racial classification diminishes from geographic to ethnic.3 For the past two decades, the greatest genetic differentiation has occurred between continentally separated

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