Race

The term race describes populations or groups of people as distinguished by various sets of characteristicsoriginal research?] and beliefs about common ancestry.citation needed] The most widely used human racial categoriesoriginal research?] are based on visible traits (especially skin color, facial features and hair texture), and self-identification.citation needed]

However, the first detailed analysis of the entire human genetic code — by the United States National Institutes of Health and the Department of Energy — and by Celera Genomics of Rockville, Maryland, a private company, "strengthens the notion that race has no genetic basis," even among people who identify themselves as of one race or ethnicity or another.

Conceptions of race, as well as specific ways of grouping races, vary by culture and over time, and are often controversial for scientific as well as social and political reasons. Some argue that although "race" is a valid taxonomic concept in other species, it cannot be applied to humans. Mainstream scientists have argued that race definitions are imprecise, arbitrary, derived from custom, have many exceptions, have many gradations, and that the numbers of races delineated vary according to the culture making the racial distinctions; they thus reject the notion that any definition of race pertaining to humans can have taxonomic rigour and validity. Today most scientists study human genotypic and phenotypic variation using more rigorous concepts such as "population" and "clinal gradation." Many anthropologists contend that while the features on which racial categorizations are made may be based on genetic factors, the idea of race itself, and actual divisions of persons into groups based on selected hereditary features, are social constructs, whereas a new opinion among geneticists is that it should be a valid mean of classification, although in a modified form based on DNA analysis.