Afro-European Genetic Admixture in the United States

Essays on the Color Line and the One-Drop Rule
by Frank W Sweet
June 8, 2004

T

he decoding of the human genome has enabled molecular anthropologists to track prehistoric as well as recent human migrations. You carry traces of the past in your DNA—markers that identify the populations and sub-populations to which your ancestors belonged. They reveal information about your forebears: how they lived, where they came from.

This has nothing to with “race.” Some people, for example, are lactose-tolerant and can digest milk in adulthood without difficulty. Others cannot. Among the former are most Danes, Dutch, Watutsi, and Maasai. Among populations who suffer digestive discomfort if they drink milk as adults are most Sicilians, Greeks, Bantus and the Khoisan (Kalahari Bushmen). It turns out that you are more likely to be lactose-tolerant if your ancestors after the Neolithic agrarian revolution were primarily herders. If your ancestors were mainly cultivators of grains, then you are more likely to be lactose-intolerant. Similar traits reveal whether your ancestors lived at low latitudes, subjected to excess solar ultraviolet radiation, or at high latitudes, with less-than-ideal levels of ultraviolet. Other DNA markers suggest whether your ancestors lived in the thin air of mountain elevations or along the seashore, and still others tell of the diseases to which they were subjected.

The New World was first populated by hunters who migrated across Beringia about 20 millennia ago. Rising sea levels when the last ice age ended cut them off from everyone else. Isolated, their immune systems lagged behind the rest of the human species in the ongoing genetic arms race against germs. Columbus and those who followed him suddenly introduced Euro-Afro-Asian germs into the New World. Within a generation, over 90 percent of Native Americans had died of diseases that their immune systems could not recognize.1 Then, over the next three centuries, eleven million Africans and about one-fifth as many Europeans were carried across the Atlantic in sailing ships to repopulate the devastated New World.2 Most Africans came involuntarily (although some were indentured servants) and most Europeans volunteered (although some were sold into slavery). But, whether volunteers or slaves, Africans or Europeans, the immigrants came in their tens of millions and blended with the handful of surviving natives into a mixed population. The blending was nearly total in Central and South America—most Ibero-Americans enjoy demographically proportional genetic admixture from both transatlantic sources. The blending was a bit less thorough in the British West Indies, and even less so in North America.3 Of interest here is the extent of genetic admixing among people from different continents to produce the current inhabitants of North America: how, when, where, and to what extent the admixing happened.

Thirty-Nine Ancestry-Informative Markers

Thirty-Nine Ancestry-Informative Markers4

Ancestry-informative markers help to answer such questions by enabling estimates of what fraction of an individual’s genome was inherited from Africa, what fraction came from Europe, and what fraction descended from the pre-Columbian aboriginal population. The table above shows a typical array of 39 DNA markers used to identify the ancestral continent of origin of New-World peoples.

Eight columns are of interest, exemplified by the table’s third row. The first column gives the common-use name of the marker. FY-NULL*1 denotes a particular variant of a gene that encodes a protein associated with the Duffy blood group. Column three shows where the marker is located in the genome. The entry 1q23.2 means that this marker is located on the first chromosome (1), on the long arm of the chromosome (q), and 23.2 centimorgans5 from the chromosome’s centromere. Columns five, six, and seven show the marker’s rate of incidence in the native populations of sub-Saharan Africa, Europe, and America. Only one African in a thousand carries the FY-Null marker, while every Native American tested does so, as do 998 out of every thousand Europeans. Columns eight, nine, and ten show the marker’s effectiveness in distinguishing between any two of the three populations. FY-Null is very effective at distinguishing between Africans and either Europeans or Native Americans (0.997 and 0.999, respectively), but useless at distinguishing Europeans from Native Americans (0.001).

Twenty-Two Ancestry-Informative Markers

Twenty-Two Ancestry-Informative Markers

The next table shows a smaller array of 22 DNA markers, used by a different research team than the source of the prior table, but also to identify the ancestral continent of origin of New-World peoples.6 That some researchers use more markers than others is a source of discussion in the field. Should you stick to the small handful of extremely reliable and informative markers? Or should you also examine (for any given individual) the greater number of marginally reliable markers, on the grounds that they are cumulatively informative? Say, for instance, that each marker of a set of twenty markers is only 67 percent reliable in distinguishing European from African ancestry. If a person has the European version, he or she may be among the two-thirds of Europeans who have the marker or among the one-third of Africans who also have it. But if all twenty of the individual’s 67-percent-reliable markers point to European ancestry, their unanimity becomes much more persuasive.7

Again, it is important to recognize that such markers in the DNA of today’s inhabitants of the New World cannot identify one’s “race,” not even implicitly. They show only the continent of origin of your ancestors (Africa, Europe, or Native America). Consider, for instance, row 18 of the second table, labeled MC1R314. This is the same marker that is depicted as MC1R-314*1 in row 33 of the first table. About 51 percent of Africans, but only 16 percent of Europeans carry this particular marker in their DNA. In other words, if you have this marker at position 16q24.3 of your sixteenth chromosome, then it is two-out-of-three likely that you inherited it from a sub-Saharan ancestor. As it turns out, MC1R314 is one of the few markers associated with a gene whose function is known. It is one of the half-dozen genes associated with dark skin tone. (TYR at 11q14-21, TYRP1 at 9p23, TYRP2 at 13q31-32, “P” at 15q11.2-12, and OCA2 at 15q13.1 also govern dermal melanization.8) In other words, row 33 of the second table merely says, in essence, that if you are a New-World inhabitant with a dark brown complexion, you probably inherited it from a sub-Saharan ancestor. The point is that the above markers were chosen because they work, nothing more—even those whose function is unknown. The markers were chosen only because they correlate strongly with continent of origin.

Another important point is that the above-listed genetic markers are not the ones that you would use in order to track prehistoric migrations. For such a purpose you would choose different of sets markers, depending upon the time frame of interest. For example, the markers that you would use to track the African Diaspora that colonized the planet starting 60 millennia ago are different from those used to follow the tribes who re-colonized uninhabited central Europe after the glaciers retreated 16 millennia ago.9

Skin Tone as Function of Afro-European Admixture

Skin Tone as Function of Afro-European Admixture10

The main use of ancestry-informative markers today is in medical research. They help determine whether any given disease (HIV, diabetes, obesity, cystic fibrosis, etc.) is more or less prevalent, or has a consistently different outcome, depending upon a person’s continent of ancestry. One way of doing this is with a scatter diagram. Say, for example, that you test a few thousand individuals. You measure each person’s Afro-European admixture percentage using ancestry-informative DNA markers. You also measure each person’s susceptibility to some disease of interest. You then plot each individual on a graph from left-to-right based upon genetic admixture. People of 100 percent European (0 percent African) ancestry are plotted on the left-hand axis. People of 100 percent African (0 percent European) ancestry are plotted on the right-hand axis. Everyone else goes somewhere in between, left-to-right depending on admixture ratio. Each dot is also plotted vertically depending on susceptibility to the disease of interest. Those with no vulnerability to the disease are plotted along the bottom axis. Those who have the strongest susceptibility are plotted along the top axis. Everyone else is plotted in between, bottom-to-top depending on disease susceptibility. This process yields a scatter diagram, a cloud of dots spread across the chart. If the cloud trends upwards and to the right, it shows that the disease in question tends to be more prevalent among those with a strong African admixture component. If it trends downwards to the right, it shows that the disease tends to be more prevalent among those of predominantly European admixture component. If it trends in neither direction, then it shows that there is no connection between Afro-European genetic admixture and that particular disease. Such studies have revealed that diabetes, prostate cancer, and hypertension, for example, are more prevalent among Americans of predominantly African genetic admixture, while dementia and osteoporosis are more frequent among those of mostly European genetic admixture.

Mark D. Shriver

Dr. Mark D. Shriver

The scatter diagram above shows skin tone as function of Afro-European admixture ratio. It is a a typical Afro-European genetic admixture scatter diagram. It was taken from an article produced out of a project headed by Penn State University molecular anthropologist Mark D. Shriver, shown at right.

Among the other sixteen team-members and collaborators of this study, who work for colleges and private research laboratories throughout the United States, Canada, and England, is Dr. Rick Kittles, a geneticist at Howard University in Washington DC (see photograph below, at left). The study analyzed DNA samples from 3,000 individuals in 25 locations. In the graph above, the vertical scale does not represent susceptibility to any specific disease. Instead, individuals were plotted bottom-to-top based upon how dark was the person’s complexion (as measured by the reflectance of the inner upper arm). Darker individuals are plotted higher than paler ones. The team’s intent was to see if dermal melanin correlated with percentage of African genetic admixture, and so might be a predictor of, say, skin cancer. The cloud of points displays a visibly distinct slope rising from lower-left to upper-right. This demonstrates that, in general, the more African genetic admixture you have, the darker your skin.11

Rick A Kittles

Dr. Rick A Kittles

The graph also depicts another variable, one that is of interest to the historian—endogamous group membership or ethnic self-identity. Each dot in the chart is encoded to show whether the person sampled claimed to be a member of the U.S. White endogamous group (diamond shape, 187 individuals) or of the U.S. Black endogamous group (open circle, 232 individuals). (The x-shaped plots represent a population of British West Indian ethnicity living in London.12) The graph refers to these three groups as European American, African American, and African Caribbean, respectively, and the text explains that this trait was self-assessed and independent of actual genetics.

With this added information, three aspects of the scatter diagram suddenly jump out at you. First, there is significant overlap between White and Black Americans regarding Afro-European genetic admixture. Some so-called “Black” Americans have less DNA admixture of African ancestral origin than do some so-called “White” Americans. Second, the admixture range of Black Americans spans the entire chart. While most of the subjects who self-identify as Black (marked as circles) have strong African admixture (are found towards the right), some have little or no African admixture (are found at the left edge). Finally, although the range of genetic admixture in those who self-identify as “White” is narrower than the admixture range of Blacks, it is still significant. Many so-called “White” Americans have as much as 20 percent or more of African genetic admixture.

The next graph, “Afro-European Genetic Admixture as a Function of Ethnicity” below, was taken from a different study. It also matches ancestral continent-of-origin genetic admixture for several hundred individuals with their ethnic self-identity or endogamous group membership.

Afro-European Genetic Admixture as a Function of Ethnicity

Afro-European Genetic Admixture as a Function of Ethnicity13

In the scatter diagram at right, each point (representing one individual) is plotted vertically to depict Afro-European genetic admixture (100 percent European at the top) and horizontally into four groups representing endogamous group membership or ethnicity. The groups, from left to right, are: 147 Americans of the White endogamous group, 264 Americans of the Black endogamous group, 135 subjects from Zaire (formerly Congo), and 159 subjects from Nigeria.14

Three points of interest present themselves upon your examining this graph. First, as in the prior chart, there is genetic admixture overlap between Americans of the Black and White endogamous groups within the range of from zero to thirty percent African genetic admixture. As in the Shriver study of skin tone, some so-called “White” Americans have over twenty percent African genetic admixture and some so-called “Black” Americans have little or none. Indeed, other studies have found that approximately 5.5 percent of members of the U.S. Black community have no detectable African genetic admixture.15

Second, the Black and White groups are not symmetrical. The mean African admixture among White Americans is low—roughly 0.7 percent African and 99.3 percent European admixture.16 To put this in perspective, this would have been the result if every member of the U.S. White endogamous group alive today had a single ancestor of one hundred percent African genetic admixture seven generations ago (around the year 1850). Of course, African alleles are not distributed evenly. Seventy percent of White Americans (like 5.5 percent of Blacks) have no detectable African genetic admixture at all. Among the thirty percent of Whites with African genetic admixture, the admixture ratio averages to about 2.3 percent, the equivalent of having a single ancestor of one hundred percent African genetic admixture from around the year 1880.17 Black Americans, on the other hand, have significant European admixture (averaging about 75 percent African and 25 percent European).

Third, the wide admixture spread of the two groups of New-World inhabitants contrasts with the narrow range of admixtures among Old-World inhabitants. A wide spread of genetic admixtures is characteristic of the Western Hemisphere. As evident in the chart, on the one hand, the U.S. White population spans a range of 15-20 percent and the U.S. Black population covers a 30-40-percent range. On the other hand, the Nigerian population covers only a 10-precent spread and the Congolese population spans only a 5-percent range.

The Black and White ranges are typical of the New World. Admixture variation among Latin American populations tends to span ranges as broad as that of the U.S. Black endogamous group, but shifted up or down on the chart depending on the particular nation’s colonial ratio of African slaves to European colonists. A plot from Argentina, for example, would resemble a mirror image of the Black scatter diagram, flipped over to start at the top, thereby resembling a slightly stretched version of the White U.S. plot. Scatter diagrams of Puerto Ricans or Dominicans center on the 50-percent line, with decreasing dot densities stretching all the way to both of the 100-percent axes. Haitians produce scatter diagrams resembling those of Black Americans.

Old-World populations, in contrast, display much narrower ranges of variation of genetic admixture. A scatter diagram of Danes or Dutch would resemble a flipped mirror-image of the Zairean population, with a mere 5-percent spread from the 100-percent European axis. A diagram of Spain or Portugal would resemble a flipped, slightly stretched version of the Nigerian diagram.18

What is remarkable about the two U.S. endogamous groups is not that each spans a wide range of Afro-European admixture. That many White Americans carry up to 20 percent African genetic admixture may startle the uninformed, but this is typical of New World populations descended from demographically European colonies with few African slaves. And the admixture plot of Black Americans resembles those of the West Indies, where African slaves were a demographic majority. What is remarkable about the two U.S. groups is that they both live within the same society. Such a bimodal distribution of Afro-European admixture is characteristic of no other nation on earth. The separation, of course, is the result of the endogamous U.S. color line.

Genetic Admixture is not the Same as Appearance

About one-third of White Americans are of between two and twenty percent recent African genetic admixture, as measured by the ancestry-informative markers in their DNA.19 This comes to about 74 million Americans. And yet, day-to-day experience teaches that virtually all White Americans look, well, White. Some may look more Mediterranean and others may look more Nordic, but very few White Americans have a distinctively African appearance. How can one reconcile DNA measurements with common experience?An anecdote may help illustrate the problem. Look again at the chart of Skin Tone as Function of Afro-European Admixture. Consider one of the graph’s outlier points—a “European American” individual plotted as having 11 percent20 African genetic admixture. Dr. Shriver, the project team leader, became curious about this individual for two reasons. First, the person’s African genetic admixture was unusually high for someone who self-identified as a member of the U.S. White endogamous group. Second, the sample had been taken from State College, Pennsylvania, the site of Dr. Shriver’s own campus.21 According to Dr. Shriver:

I had the result for two or three years before I even looked up the ID number of the person whom we tested. I looked at who it was and it was me! I checked myself and the rest of my relatives and tracked it through my family. I never considered that there were any African people in my family. There’s no real variation in my family. The admixture must have been pretty far back. It just so happens that we can detect it with the markers we have. My mom especially stood out as being surprised, maybe because I told her it was coming through her father. She still doesn’t believe it about her family! The part of Pennsylvania where my mother’s father came from is where the Underground Railroad ended. There are several towns right here in Southern Pennsylvania where there are very light-skinned African-American communities that are the remnants of the Underground Railroad.22

It seems that Dr. Shriver’s maternal grandfather moved from Pennsylvania to Iowa, then to California, leaving behind in the process most of his ties with his relatives.23 Dr. Shriver, it turns out, (see photograph above) is one of the 74 million White Americans with significant recent African genetic admixture.In a coincidentally similar fashion, Dr. Rick Kittles, Shriver’s collaborator from Howard University in Washington, discovered that he carries the FY-null genetic marker at genome position 1q23.2. This marker is found in 998 out of every thousand Europeans but found in only one out of thousand Africans. Many of Dr. Kittles’s other ancestry-informative markers tell the same unexpected story. Dr. Kittles (see photograph above) is one of the many Black Americans with strong European genetic admixture. And yet, and there is no other way to say this, Dr. Shriver “looks White” and Dr. Kittles definitely “looks Black.” Why is there such a discrepancy between measured genetic admixture and physical appearance?There is an immediate answer to this question, and a deeper answer. The immediate answer is that many different invisible genes identify continent of ancestry. As of the summer of 2004, the private DNA lab DNAPrint Genomics, Inc. uses up to 175 single nucleotide polymorphisms (markers) in order to analyze a client’s ancestral continents of origin.24 On the other hand only a handful of genes encode for the few superficial, externally visible features (skin color, hair curliness, etc.) that Americans see as “racially” significant. Parental genes are randomly recombined with each passing generation. It can happen, through sheer chance, that an individual (like Dr. Shriver) can inherit many invisible African DNA markers, but few or none of the handful of alleles that encode for “racial” appearance. Alternatively, a person (like Dr. Kittles) can inherit those few alleles that encode for visible “racial” appearance but otherwise inherit the invisible but ancestrally informative European admixture markers.

Blacks’ Skin Tone as Function of Admixture

Blacks’ Skin Tone as Function of Admixture

The deeper answer becomes evident if you plot each of the two U.S. endogamous groups from the skin tone diagram separately. The next graph, “Blacks’ Skin Tone as Function of Admixture,” shows just one portion of the population of the earlier chart—those who self-identified as members of the U.S. Black endogamous group. In this diagram you can see a definite positive correlation (R2=0.211) between skin tone and African admixture. Clearly, if you are considered a Black American, the more African admixture you have, the higher your melanin index. More importantly, the range of skin reflectance as measured by the melanin index of Black Americans is very large, spanning a vertical distance of fifty points from 30 to 80.

“Whites’ Skin Tone as Function of Admixture,” below, shows the other U.S. endogamous group from the earlier chart—those who self-identified as White. In this diagram, you can see that there is no correlation, either way (R2=0.001), between skin tone and African admixture. Clearly, if you are considered a White American, your melanin index is unrelated to your degree of African admixture. More importantly, the range of skin reflectance as measured by the melanin index of White Americans is very narrow, spanning a vertical distance of only twenty points from 20 to 40. This is less than half of the range of skin-tone variation found among Black Americans.

Whites’ Skin Tone as Function of Admixture

Whites’ Skin Tone as Function of Admixture

The combination of narrow phenotype variation (skin tone) along with a wide range of inter-population (Afro-European) admixture variation among White Americans shows that a selection process has taken place. Few human populations display such a clear mark of selection. Narrow phenotype variation alone does not necessarily indicate selection. Northern Europeans display little skin tone variation, but they lack a wide range of African admixture. Broad genotype variation alone does not necessarily indicate selection. Puerto Ricans average 50-50 Afro-European admixture, but they also display a wide range of skin tones. The late Stephen J. Gould, Harvard biology professor and columnist for Natural History magazine, used to explain this principle with a baseball analogy. Plot a scatter diagram of the batting averages of a thousand amateur or minor-league players and you will find a very large range of variation. A few such players are very bad, a few are very good, and most spread across the entire range of batting averages in-between. Now plot the batting averages of professional athletes in the major leagues. All are very good indeed. More importantly, the range of batting averages among them is tiny. The difference between an outstanding star of the game and a rookie is a matter of mere hundredths of a percentage point. The reason, of course, is because you cannot get into the majors unless you are very good at it. Similarly, wild cows vary greatly in the amount of milk that they produce. The cows in a dairy farm produce more milk on average but, more importantly, their milk production varies very little among themselves (compared to wild cows). The reason? Those cows who do not make the cut become hamburger.

And so, why do few if any White Americans display a strongly African appearance (have a high melanin index) despite having detectable African admixture? Because those Americans who “look Black” are assigned involuntarily to the Black endogamous group, whatever their genetic admixture. The scatter diagrams of the two endogamous U.S. groups are not symmetrical because the selection process acts only upon the White group. As revealed in court records, discussed elsewhere, a person of mixed ancestry who “looks European” (like Dr. Shriver or his maternal grandfather) in practice has the option of either adopting a White self-identity, thus joining the White endogamous group or a Black self-identity, thus joining the other group. But a person of mixed ancestry who “looks African” lacks such a choice. U.S. society assigns such a person to membership in the Black endogamous group, like it or not.25

In conclusion, U.S. society has unwittingly applied selection pressure to the color line. The only American families accepted into the White endogamous group have been those whose African admixture just happened not to include the half-dozen alleles for dark skin (or the other physical traits associated with “race”). Since those particular alleles were sifted out of the portion of the White population that originated in biracial families, the relative percentage of the remaining, invisible, African alleles in this population cannot affect skin color. That skin-color does not vary with African genetic admixture among American Whites, despite their measureably recent African admixture, demonstrates and confirms that physical appearance has been an important endogamous group membership criterion throughout U.S. history. It has resulted in genetic selection of the White U.S. population for a European “racial” appearance, regardless of their underlying continent-of-ancestry admixture ratio.

Click here for an animated cartoon version of this topic.


1 Woodrow Wilson Borah and Sherburne Friend Cook, The Aboriginal Population of Central Mexico on the Eve of the Spanish Conquest(Berkeley: University of California, 1963).

2 Hugh Thomas, The Slave Trade: The Story of the Atlantic Slave Trade: 1440-1870(New York: Simon and Schuster, 1997), 793, 804-5.

3 Esteban J. Parra and others, “Estimating African American Admixture Proportions by Use of Population-Specific Alleles,” American Journal of Human Genetics 63 (1998): 1839-51; E.J. Parra and others, “Ancestral Proportions and Admixture Dynamics in Geographically Defined African Americans Living in South Carolina,” American Journal of Physical Anthropology 114 (2001): 18-29; C.L. Pfaff and others, “Population Structure in Admixed Populations: Effect of Admixture Dynamics on the Pattern of Linkage Disequilibrium,” American Journal of Human Genetics 68 (2001): 198-207.

4 A “centimorgan” is a measure of chromosomal distance tied to the likelihood of meiosis recombination.

5 From Mark D. Shriver and others, “Skin Pigmentation, Biogeographical Ancestry, and Admixture Mapping,” Human Genetics 112 (2003): 387-99.

6 For mathematical discussions of this point, see Michael J. Bamshad and others, “Human Population Genetic Structure and Inference of Group Membership,” American Hournal of Human Genetics 72 (2003): 578-89 or Jinliang Wang, “Maximum-Likelihood Estimation of Admixture Proportions From Genetic Data,” Genetics 164 (2003): 747-65.

7 From Jose R. Fernandez and others, “Association of African Genetic Admixture with Resting Metabolic Rate and Obesity Among Women,” Obesity Research 11, no. 7 (2003): 904-11.

8 Richard A. Sturm, Neil F. Box, and Michele Ramsay, “Human Pigmentation Genetics: The Difference is Only Skin Deep,” BioEssays 20 (1998): 712-21.

9 For introductions to markers tracing prehistoric migrations, see: Bryan Sykes, The Seven Daughters of Eve, 1st American ed. (New York: Norton, 2001) or Steve Olson, Mapping Human History: Discovering the Past Through Our Genes (Boston: Houghton Mifflin, 2002).

10 Mark D. Shriver and others, “Skin Pigmentation, Biogeographical Ancestry, and Admixture Mapping,” Human Genetics 112 (2003): 387-99.

11 Dozens of peer-reviewed journal articles on Afro-European genetic admixture mapping using ancestry-informative DNA markers have sprung from the decoding of the human genome. About 50 such articles from medical, genetic, and molecular anthropological journals are available for download from Various Admixture Studies.

12 The 173 individuals of West Indian ethnicity were all British subjects living in London. Some genetic admixture mapping studies lump British West Indians and African-Americans into a single group. This study tallies them separately because doing so reveals the interesting point that there are virtually no “Black” British West Indians with very slight African genetic admixture. British West Indians of known partial African ancestry who look European are considered “White” by British society, which lacks an endogamous color line.

13 Heather E. Collins-Schramm and others, “Markers that Discriminate Between European and African Ancestry Show Limited Variation Within Africa,” Human Genetics 111 (2002): 566-9.

14 Again, some would argue that Nigerians and Zaireans are also “Black” and so should be lumped in with the African-Americans. But this confuses genetic admixture and nationality with membership in one of the two U.S. endogamous groups. Nigerians and Zaireans are of preponderantly African genetic admixture with little European admixture, but they do not become members of either of the two U.S. endogamous socio-political groups unless and until they immigrate to the United States.

15 E.J. Parra and others, “Ancestral Proportions and Admixture Dynamics in Geographically Defined African Americans Living in South Carolina,” American Journal of Physical Anthropology 114 (2001): 18-29, Figure 1.

16 Mark D. Shriver and others, “Skin Pigmentation, Biogeographical Ancestry, and Admixture Mapping,” Human Genetics 112 (2003): 387-99, Table 2.

17 Steve Sailer, “Analysis: Race Now Not Black and White,” (UPI, May 8, 2002). Astonishingly, these DNA-based findings confirm an obscure 1958 study that predicted, on the basis of statistical demographics alone, that about 21 percent of White Americans had Black ancestry within the past four generations. See Robert S. Stuckert, “The African Ancestry of the White American Population,” Ohio Journal of Science 55, no. May (1958): 155-160. For an accessible survey, see Monica L. Haynes, “Passing: How Posing as White Became a Choice for Many Black Americans,” Post-Gazette, October 26 2003, Lifstyle, 1.

18 Interestingly, the slighter broader-than-usual (for the Old World) admixture range of Nigerians and Iberians probably has the same cause. Both of these broader-than-expected scatter diagrams may reflect the faint remaining traces of the population mixing that took place consequent to the Almoravid Empire and its aftermath. The Almoravid Empire (1043-1133) stretched from Senegambia to Barcelona.

19 Steve Sailer, “Analysis: Race Now Not Black and White,” (UPI, May 8, 2002)

20 The Sailer (2002) article, from which the above anecdote was taken, said “23 percent” African admixture, and so this was the number given in an earlier edition of this essay. But the number may have been mistaken. The 11 percent figure, above, is from a conversation between Dr. Shriver and the present author after a lecture in Gainesville, Florida, in November 2003, and matches the number mentioned in Christen Brownlee, “Code of Many Colors,” Science News Online April 9, 2005. See URL http://www.sciencenews.org/articles/20050409/bob9.asp for online access.

21 Steve Sailer, “Analysis: Race Now Not Black and White,” (UPI, May 8, 2002).

22 Dr. Shriver’s comments are from an interview in Sailer (2002).

23 Idem.

24 As of June 7, 2004, see the firm’s URL http://www.ancestrybydna.com/ancestry25.asp.

25 As discussed elsewhere, exceptions to this rule are made in U.S. society for some Hispanics and North African Muslims of slight African appearance.

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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.


Other Frank W Sweet sites: Essays on the U.S. Color Line Armed Citizens and the Law
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