Although in the United States people are often asked to self-identify as either white, Hispanic, African American, Asian or Native American, advanced understanding of DNA reduced the amount of races accepted by scientists to three: European, Asian, African. It is argued, however, that even these three races are not accurate classifications of individuals.
The disparity of exactly what qualifies as a race lies in the history of race as a social construct. However, the contemporary study of race involves scientific research into the variances of human DNA. Traditionally, people have been racially classified based on their appearance. It was assumed that people with similar physical features shared a common ancestor. Human genome testing, however, has established this is not necessarily true. Scientists point out that the DNA of many Europeans is no more similar to each other than is the DNA of Europeans and Africans. Additionally, the American Anthropological Association asserts that of the three currently accepted races, European and Asian are actually subsets of African, as human beings have inhabited the African continent for the longest amount of time.
Contemporary racial classifications, however, are dictated more by population distribution and by exposure to people of dissimilar heritages to each other. As understanding about the science of race has grown, scientists have begun dropping the term "race" in favor of the less derogatory "human variation."