The U.S. Black/White Color Line

Essays on the Color Line and the One-Drop Rule
by Frank W Sweet
August 15, 2008


he United States is the only nation on earth that has preserved for over three centuries a genetically discontinuous enclave of mostly African ancestry within a larger population of European ancestry.

Unique in the Western Hemisphere

The U.S. endogamous color line is unique in the Western Hemisphere. After the New World’s aboriginal population was nearly wiped out by diseases to which they lacked immunity, it was re-populated by eleven million African slaves and three million European colonists. In every nation but one, the populations promptly interbred, yielding today’s unimodal genetic admixture scatter diagrams.

Where African slaves were few, as in Argentina or Chile, scatter diagrams show a single cluster skewed towards European admixture. The average Argentinean or Chilean has about 94 percent European and 6 percent African DNA markers. Virtually no long-established families look Black.

Where African slaves were many, as in Haiti, scatter diagrams show a single cluster skewed towards African admixture. The average Haitian has mostly African DNA markers and few European markers. Few long-established families look White.

Where colonial populations from Europe and from Africa were roughly equal, as in Puerto Rico or Brazil, the single genetic cluster centers on the 50-50 mark. About one family in ten looks Black, about one in ten looks White, and the rest look Hispanic or mixed.

Only the United States has a bimodal cluster diagram showing two genetically distinct groups. Most of the U.S. population has negligible detectable African DNA, while the enclave (about one-eighth of the population) is of overwhelmingly African ancestry.

Unique Around the World

The U.S. endogamous color line is also unique outside of the Western Hemisphere. Other former Euro-African colonies around the world officially recognize citizens of dual ancestry. Only in the United States do citizens of mixed Afro-European ancestry lack legal existence. Only in the United States do people say that someone “looks utterly White but is really Black,” in some invisible sense. In other nations, if you look White you are White. In other nations with populations from both Europe and Africa, the intermarriage rate is about 40 percent. This 40 percent exogamy rate is typical of ethnic assimilation of any immigrants everywhere. In contrast, U.S. Black/White intermarriage is under 4 percent and has been under 4 percent for centuries.

The only phenomenon on earth that approximates U.S. society’s harsh enforcement of its endogamous barrier is the Hindu caste system. Oddly, the latter is falling in importance due to efforts by the government of India to outlaw it. In contrast, the U.S. color line is increasingly enforced at every level of U.S. government, and any opposition to involuntary dichotomous “racial” classification by the State is usually deemed “racist” and often ruled to be illegal.

So Strange That it Demands Study

The U.S. endogamous color line is so strange that it demands study. Questions crying out for answers include: When was the unique U.S. endogamous color line invented? Where? By whom? Why? Was it the same in the many culturally distinct antebellum regions of the nation (such as Spanish Florida or the Francophone Gulf Coast)? Given the factual reality that one-third of White Americans and all Black Americans are of mixed Euro-Afro ancestry, by what yardstick do Americans shoehorn themselves into one side or the other of the color line? And, most importantly, why do Americans so tenaciously defend their dichotomy?

What makes it bizarre is that, to Americans, their dichotomous color line (which has somehow managed to preserve a unique genetically African enclave for centuries) is the norm. In their minds, everyone else on the planet is out of step. And so Americans seek explanation for their nation’s unique phenomenon in studies of slavery (historically ubiquitous), colonialism (globally ubiquitous), or “racism” (taking care to avoid defining the term). It is as though there were an odd smell in their own home but no one else’s, so they seek its source in every neighbor’s house but not their own.

Again, what is unique about the United States is not ethnicity, nor identity politics, nor White mistreatment of Blacks, nor Black hatred of Whites. What is unique and so demands explanation is the very existence of two genetically distinct endogamous groups within the same nation.


Frank W. Sweet is the author of Legal History of the Color Line (ISBN 9780939479238), an analysis of the nearly 300 appealed cases that determined Americans’ “racial” identity over the centuries. It is the most thorough study of the legal history of this topic yet published. He was accepted to Ph.D. candidacy in history with a minor in molecular anthropology at the University of Florida in 2003 and has completed all but his dissertation defense. He earned an M.A. in History from American Military University in 2001. He is also the author of several state park historical booklets and published historical essays. He was a member of the editorial board of the magazine Interracial Voice, and is a regular lecturer and panelist at historical and genealogical conferences. To send email, click here.

One Response to “The U.S. Black/White Color Line”

  1. alex Says:

    You might want to look at the writings of Steve Sailor, he had a page called isteve dot com. He came at the racial divide issue from football; with his observation that a lot of white kids who’d make good players were being passed over because of the assumption that being white, they were less likely to do well than a black player.

    His work is controversial, much of it may be opinion and not as well-researched as yours, and it may tick you, or your readers, off. But it’s out there and deserves a look, if only to see one of the strains of thought that are floating around out on the interwebs.

    The main thing I see in his writings though, isn’t so much the thing about black/white football players, which seems to be self-correcting, but what Steve’s observed in societies all through the Americas. He’s observed that in South America, the societies seem to have come to an equilibrium where the higher the social class, the lighter the skin color. And, a relatively small, light-skinned, ruling class. He says the US is changing this way, and last will be Canada. This is disturbing to me, and I’d think to many, because hierarchal societies with ruling classes don’t tend to be very happy ones.