One-drop Rule - Racial Mixtures of Blacks and Whites in Modern America

Racial Mixtures of Blacks and Whites in Modern America

Given the intense interest in ethnicity, genetic genealogists and other scientists have studied population groups. Henry Louis Gates, Jr. publicized such genetic studies on his two series African American Lives, shown on PBS. The specialists summarized United States population figures this way:

• 58 percent of African Americans have at least 12.5% European ancestry (equivalent of one great-grandparent);
• 19.6 percent of African Americans have at least 25% European ancestry (equivalent of one grandparent);
• 1 percent of African Americans have at least 50% European ancestry (equivalent of one parent) (Gates is one of those, he discovered); and
• 5 percent of African Americans have at least 12.5% Native American ancestry (equivalent to one great-grandparent).

Mark D. Shriver, a molecular anthropologist at Penn State University, has studied population with a team of researchers. In 2002 they published results of a study regarding the racial admixture of Americans who identified as white or black. They recorded the individual's self-identification and analyzed the genetic make-up of their chromosomes. Their results are estimates and might not be completely accurate. Other researchers have also done population studies.

Shriver surveyed a 3,000-person sample from 25 locations in the United States and tested subjects for genetic make-up. Among those who self-identified as white, the black racial admixture was about 0.7%; which is the equivalent of having 1 black and 127 white ancestors among one's 128 5×great-grandparents. Nationwide, Shriver estimates that 70% of white Americans have no African ancestors (in part because of the greatly increased immigration from Europe in the late 19th and early 20th centuries). Among the 30% who do have African ancestry, Shriver estimates their black racial admixture is 2.3%; the equivalent of having had 3 black ancestors among their 128 5×great-grandparents.

Blacks are more racially mixed than whites, reflecting historical experience in the United States, including the close living and working conditions among colonial indentured servants, both black and white, and slaves, when many married or formed unions. Most of the free African-American families in Virginia in colonial years were the descendants of white women and African men. After the American Revolutionary War, their descendants migrated to nearby states along with other Virginia pioneers. The admixture also reflects conditions under slavery, when white planters or their sons, or overseers, often raped African women. There were also freely chosen relationships among individuals of different or mixed races.

Shriver's study is not complete. In his study, of those persons who identified as black, their total ancestry reveals 18% white ancestry, the equivalent of having 22 white ancestors among their 128 5×great-grandparents. About 10% of blacks have more than 50% white ancestors. Population studies by researchers other than Shriver have found that in general, blacks had an average white ancestry of 25–30%.

Shriver points out that his survey found different admixture rates by region, which would also reflect historic patterns of settlement and change, both in terms of populations who migrated and their descendants' marriages. For example, the black populations with the highest average white ancestry lived in California and Seattle, both destinations during the Great Migration of 1940-1970. Blacks sampled in those two locations had more than 25% white European ancestry on average.