F. James Davis is a retired professor of sociology at Illinois State University. He is the author of numerous books, including Who is Black? One Nation's Definition (1991), from which this excerpt was taken. Reprinted with permission of Penn State University Press

To be considered black in the United States not even half of one's ancestry must be African black. But will one-fourth do, or one-eighth, or less? The nation's answer to the question 'Who is black?" has long been that a black is any person with any known African black ancestry. This definition reflects the long experience with slavery and later with Jim Crow segregation. In the South it became known as the "one-drop rule,'' meaning that a single drop of "black blood" makes a person a black. It is also known as the "one black ancestor rule," some courts have called it the "traceable amount rule," and anthropologists call it the "hypo-descent rule," meaning that racially mixed persons are assigned the status of the subordinate group. This definition emerged from the American South to become the nation's definition, generally accepted by whites and blacks. Blacks had no other choice. As we shall see, this American cultural definition of blacks is taken for granted as readily by judges, affirmative action officers, and black protesters as it is by Ku Klux Klansmen.

Let us not he confused by terminology. At present the usual statement of the one-drop rule is in terms of "black blood" or black ancestry, while not so long ago it referred to "Negro blood" or ancestry. The term "black" rapidly replaced "Negro" in general usage in the United States as the black power movement peaked at the end of the 1960s, but the black and Negro populations are the same. The term "black" is used in this book for persons with any black African lineage, not just for unmixed members of populations from sub-Saharan Africa. The term "Negro," which is used in certain historical contexts, means the same thing. Terms such as "African black," "unmixed Negro," and "all black" are used here to refer to unmixed blacks descended from African populations.

We must also pay attention to the terms "mulatto" and "colored." The term "mulatto" was originally used to mean the offspring of a "pure African Negro" and a "pure white." Although the root meaning of mulatto, in Spanish, is "hybrid," "mulatto" came to include the children of unions between whites and so-called "mixed Negroes." For example, Booker T. Washington and Frederick Douglass, with slave mothers and white fathers, were referred to as mulattoes. To whatever extent their mothers were part white, these men were more than half white. Douglass was evidently part Indian as well, and he looked it. Washington had reddish hair and gray eyes. At the time of the American Revolution, many of the founding fathers had some very light slaves, including some who appeared to be white. The term "colored" seemed for a time to refer only to mulattoes, especially lighter ones, but later it became a euphemism for darker Negroes, even including unmixed blacks. With widespread racial mixture, "Negro" came to mean any slave or descendant of a slave, no matter how much mixed. Eventually in the United States, the terms mulatto, colored, Negro, black, and African American all came to mean people with any known black African ancestry. Mulattoes are racially mixed, to whatever degree, while the terms black, Negro, African American, and colored include both mulattoes and unmixed blacks. As we shall see, these terms have quite different meanings in other countries.

Whites in the United States need some help envisioning the American black experience with ancestral fractions. At the beginning of miscegenation between two populations presumed to be racially pure, quadroons appear in the second generation of continuing mixing with whites, and octoroons in the third. A quadroon is one-fourth African black and thus easily classed as black in the United States, yet three of this person's four grandparents are white. An octoroon has seven white great-grandparents out of eight and usually looks white or almost so. Most parents of black American children in recent decades have themselves been racially mixed, but often the fractions get complicated because the earlier details of the mixing were obscured generations ago. Like so many white Americans, black people are forced to speculate about some of the fractions-- one-eighth this, three-sixteenths that, and so on....

Not only does the one-drop rule apply to no other group than American blacks, but apparently the rule is unique in that it is found only in the United States and not in any other nation in the world. In fact, definitions of who is black vary quite sharply from country to country, and for this reason people in other countries often express consternation about our definition. James Baldwin relates a revealing incident that occurred in 1956 at the Conference of Negro-African Writers and Artists held in Paris. The head of the delegation of writers and artists from the United States was John Davis. The French chairperson introduced Davis and then asked him why he considered himself Negro, since he certainly did not look like one. Baldwin wrote, "He is a Negro, of course, from the remarkable legal point of view which obtains in the United States, but more importantly, as he tried to make clear to his interlocutor, he was a Negro by choice and by depth of involvement--by experience, in fact."

The phenomenon known as "passing as white" is difficult to explain in other countries or to foreign students. Typical questions are: "Shouldn't Americans say that a person who is passing as white is white, or nearly all white, and has previously been passing as black?" or "To be consistent, shouldn't you say that someone who is one-eighth white is passing as black?" or "Why is there so much concern, since the so-called blacks who pass take so little negroid ancestry with them?" Those who ask such questions need to realize that "passing" is much more a social phenomenon than a biological one, reflecting the nation's unique definition of what makes a person black. The concept of "passing" rests on the one-drop rule and on folk beliefs about race and miscegenation, not on biological or historical fact.

The black experience with passing as white in the United States contrasts with the experience of other ethnic minorities that have features that are clearly non-caucasoid. The concept of passing applies only to blacks--consistent with the nation's unique definition of the group. A person who is one-fourth or less American Indian or Korean or Filipino is not regarded as passing if he or she intermarries and joins fully the life of the dominant community, so the minority ancestry need not be hidden. It is often suggested that the key reason for this is that the physical differences between these other groups and whites are less pronounced than the physical differences between African blacks and whites, and therefore are less threatening to whites. However, keep in mind that the one-drop rule and anxiety about passing originated during slavery and later received powerful reinforcement under the Jim Crow system.

For the physically visible groups other than blacks, miscegenation promotes assimilation, despite barriers of prejudice and discrimination during two or more generations of racial mixing. As noted above, when ancestry in one of these racial minority groups does not exceed one-fourth, a person is not defined solely as a member of that group. Masses of white European immigrants have climbed the class ladder not only through education but also with the help of close personal relationships in the dominant community, intermarriage, and ultimately full cultural and social assimilation. Young people tend to marry people they meet in the same informal social circles. For visibly non-caucasoid minorities other than blacks in the United States, this entire route to full assimilation is slow but possible.

For all persons of any known black lineage, however, assimilation is blocked and is not promoted by miscegenation. Barriers to full opportunity and participation for blacks are still formidable, and a fractionally black person cannot escape these obstacles without passing as white and cutting off all ties to the black family and community. The pain of this separation, and condemnation by the black family and community, are major reasons why many or most of those who could pass as white choose not to. Loss of security within the minority community, and fear and distrust of the white world are also factors.

It should now be apparent that the definition of a black person as one with any trace at all of black African ancestry is inextricably woven into the history of the United States. It incorporates beliefs once used to justify slavery and later used to buttress the castelike Jim Crow system of segregation. Developed in the South, the definition of "Negro" (now black) spread and became the nation's social and legal definition. Because blacks are defined according to the one-drop rule, they are a socially constructed category in which there is wide variation in racial traits and therefore not a race group in the scientific sense. However, because that category has a definite status position in the society it has become a self-conscious social group with an ethnic identity.

The one-drop rule has long been taken for granted throughout the United States by whites and blacks alike, and the federal courts have taken "judicial notice" of it as being a matter of common knowledge. State courts have generally upheld the one-drop rule, but some have limited the definition to one thirty-second or one-sixteenth or one-eighth black ancestry, or made other limited exceptions for persons with both Indian and black ancestry. Most Americans seem unaware that this definition of blacks is extremely unusual in other countries, perhaps even unique to the United States, and that Americans define no other minority group in a similar way. . . .

We must first distinguish racial traits from cultural traits, since they are so often confused with each other. As defined in physical anthropology and biology, races are categories of human beings based on average differences in physical traits that are transmitted by the genes not by blood. Culture is a shared pattern of behavior and beliefs that are learned and transmitted through social communication. An ethnic group is a group with a sense of cultural identity, such as Czech or Jewish Americans, but it may also be a racially distinctive group. A group that is racially distinctive in society may be an ethnic group as well, but not necessarily. Although racially mixed, most blacks in the United States are physically distinguishable from whites, but they are also an ethnic group because of the distinctive culture they have developed within the general American framework.