Hundreds of thousands of blacks have passed for white, from the days of slavery into the present.

According to Carla K. Bradshaw, a clinical psychologist and professor at the University of Washington, “Passing is the word used to describe an attempt to achieve acceptability by claiming membership in some desired group while denying other racial elements in oneself thought to be undesirable. The concept of passing uses the imagery of camouflage, of concealing true identity or group membership and gaining false access. Concealment of ‘true’ identity is considered synonymous with compromised integrity and impostorship. . . . If an ideal world existed free from the psychology of dominance, where racial differences carried no stigma and racial purity was irrelevant, the concept of passing would have no meaning. In fact, passing of any kind loses meaning in the context of true egalitarianism.”

In his history of the subject, Mixed Blood , Paul Spickard finds that passing has been going on in this country since the first contact between Africans and Europeans. He describes two distinct forms: discontinuous and continuous passing. Discontinuous passing is defined as being “white” only part of the time—on the job, for instance, at cultural or entertainment events, or in segregated facilities, such as schools, shops, and transportation. Continuous passing, as happened in my mother’s family, means a complete break with the African-American community. Such racial alchemy doesn’t happen without great emotional and psychological cost. Cutting oneself off from one’s culture, one’s family, and one’s community is tantamount to shutting oneself into a racial closet whose door is never securely locked.

This is not a subject that has received much attention in popular literature, perhaps because it is simply too unsettling. We saw it treated on the Broadway stage in Show Boat , whose most riveting character is Julie, the beautiful light-skinned mulatto singer married to a white man. Her racial “secret” is exposed, causing her to lose her marriage, her job, and ultimately her more privileged way of life. A few films, including Pinky, Imitation of Life , and, more recently, Shadows , deal with “white” heroines whose dark genetic pasts return to haunt and undo their lives. Of course millions of light-skinned blacks never have chosen to pass. And some have become national figures, such as the New York City congressman Adam Clayton Powell, Jr., and the civil rights leader Walter White. For millions of others, however, passing has been a way to cope with the poisonous legacy of slavery.

Some geneticists claim that as many as 80 percent of black Americans have white bloodlines and that a surprising 95 percent of white Americans have some black ancestry. These statistics are based not on guesswork but on the direct clinical examination of nucleotides and microsatellites, genetic components common to all human blood. Dr. Luigi Cavalli-Sforza tells us in The History and Geography of Human Genes , the first genetic atlas of the world, just published by Princeton University Press, that all ethnic groups hold an array of overlapping sets and subsets of mixed gene pools. He notes that modern Europeans (the ancestors of America’s immigrants) have long been a mixed population whose genetic ancestry is 65 percent Asian and 35 percent African. There never has been any such thing as a “Caucasoid” gene. Nor is there such a creature as a “pure” white or black American. During recent hearings of the Senate Committee on Government Affairs on the Human Genome Diversity Project, Dr. Cavalli-Sforza and Dr. Mary-Claire King, a geneticist at the University of California at Berkeley, discussed the implications of their work. They called racism “an ancient scourge of humanity” and expressed the hope that further extensive study of world populations would help “undercut conventional notions of race and underscore the common bonds between all humans.”

Just from looking at archival records of my family, I know that every census has measured race differently. In different periods the same people in my family were listed as mulatto, black, or white. The designation could depend on the eye of the beholder or the neighborhood where they lived. In the meantime, their neighbors, their coworkers, and their communities at large saw them as either black or white, depending on who decided what. (Currently, a multiracial activist group is lobbying Congress to add a “mixed race” category for all those who do not wish to choose one side or the other of their gene pools.)

Because of the newness and yet somehow remembered, dreamed, imagined, or experienced familiarity of this story, The Sweeter the Juice has captured the interest of white and blacks all over the country. Thus the flood of letters and phone calls. Many of the callers begin their conversations with the phrase “I’m white, I think.” And with the letters come copies of old photographs, census documents, family trees, family secrets, and family confessions.