Do black/white differences in telomere length depend on socioeconomic status?

Social and economic disadvantage are hypothesized to increase the risk of disease and death via accelerated biological aging. Given that US blacks are socially and economically disadvantaged relative to whites, health disparities scholars expected that blacks would have shorter telomere length-a biomarker of cell aging-than whites. Yet the majority of studies have found that blacks have longer telomere length than whites. Using data from the National Health and Nutrition Examination Survey (n = 3,761; 28.3% non-Hispanic black, 71.7% non-Hispanic white), we found that leukocyte telomere length was 4.00% (95% CI: 1.12%, 6.87%) longer among blacks compared to whites in the full sample, but differences were greatest among those with lower SES (5.66%; 95% CI: 0.10%, 10.32%), intermediate among those with middle SES (4.14%; 95% CI: 0.05%, 8.24%), and smallest among those with higher SES (2.33%; 95% CI: -3.02%, 7.67%). These results challenge purely genetic explanations for race differences in telomere length and point to a potential social-environmental cause of longer telomere length in US blacks.

The peopling of the African continent and the diaspora into the new world

Africa is the birthplace of anatomically modern humans, and is the geographic origin of human migration across the globe within the last 100,000 years. The history of African populations has consisted of a number of demographic events that have influenced patterns of genetic and phenotypic variation across the continent. With the increasing amount of genomic data and corresponding developments in computational methods, researchers are able to explore long-standing evolutionary questions, expanding our understanding of human history within and outside of Africa. This review will summarize some of the recent findings regarding African demographic history, including the African Diaspora, and will briefly explore their implications for disease susceptibility in populations of African descent.

Evolutionary constraints in the β-globin cluster: the signature of purifying selection at the δ-globin (HBD) locus and its role in developmental gene regulation

Human hemoglobins, the oxygen carriers in the blood, are composed by two α-like and two β-like globin monomers. The β-globin gene cluster located at 11p15.5 comprises one pseudogene and five genes whose expression undergoes two critical switches: the embryonic-to-fetal and fetal-to-adult transition. HBD encodes the δ-globin chain of the minor adult hemoglobin (HbA2), which is assumed to be physiologically irrelevant. Paradoxically, reduced diversity levels have been reported for this gene. In this study, we sought a detailed portrait of the genetic variation within the β-globin cluster in a large human population panel from different geographic backgrounds. We resequenced the coding and noncoding regions of the two adult β-globin genes (HBD and HBB) in European and African populations, and analyzed the data from the β-globin cluster (HBE, HBG2, HBG1, HBBP1, HBD, and HBB) in 1,092 individuals representing 14 populations sequenced as part of the 1000 Genomes Project. Additionally, we assessed the diversity levels in nonhuman primates using chimpanzee sequence data provided by the PanMap Project. Comprehensive analyses, based on classic neutrality tests, empirical and haplotype-based studies, revealed that HBD and its neighbor pseudogene HBBP1 have mainly evolved under purifying selection, suggesting that their roles are essential and nonredundant. Moreover, in the light of recent studies on the chromatin conformation of the β-globin cluster, we present evidence sustaining that the strong functional constraints underlying the decreased contemporary diversity at these two regions were not driven by protein function but instead are likely due to a regulatory role in ontogenic switches of gene expression.

Educational inequality by race in Brazil, 1982-2007: structural changes and shifts in racial classification

Despite overwhelming improvements in educational levels and opportunity during the past three decades, educational disadvantages associated with race still persist in Brazil. Using the nationally representative Pesquisa Nacional de Amostra por Domicílio (PNAD) data from 1982 and 1987 to 2007, this study investigates educational inequalities between white, pardo (mixed-race), and black Brazilians over the 25-year period. Although the educational advantage of whites persisted during this period, I find that the significance of race as it relates to education changed. By 2007, those identified as blacks and pardos became more similar in their schooling levels, whereas in the past, blacks had greater disadvantages. I test two possible explanations for this shift: structural changes and shifts in racial classification. I find evidence for both. I discuss the findings in light of the recent race-based affirmative action policies being implemented in Brazilian universities.

The population dynamics of black-white-mulatto racial systems

Building on Preston and Campbell's two-sex model of intergenerational transmission, this article provides a theoretical analysis of the dynamics of the racial distribution in black-white-mulatto systems. The author shows that "bounded" patterns of racial classification and switching imply long-run racial homogeneity in the absence of differential reproduction. Beyond the theoretical analysis, the author attempts to account for the dramatic growth of the white population share in Puerto Rico in the early 20th century. Because the effects of racial classification and differential reproduction were roughly offsetting, the observed growth of the white share can be attributed almost entirely to racial switching.

The foundation of modern racial categories and implications for research on black/white disparities in health

The persistence of black/white disparities in health outcomes has led some to question the approaches public health, biomedical and clinical researchers use to classify, describe, and analyze race. Although these fields appear ready for the emergence of new strategies for studying race, they must first develop a solid understanding of the historical bases for the concept. This article adds to the health disparities discourse by explaining the origins of the US race and ethnicity concepts and clarifying ways in which race is 'real.' The idea of distinct and hierarchically valued races is a dominant, though problematic paradigm for explaining human diversity. We propose that the construct of race is inseparable from the term's origins and, in research must be treated as such. Doing so appropriately may enhance cross-disciplinary efforts to target the fundamental causes of racial disparities in health. We draw on multi-disciplinary research to explain how race became fixed within the American mind, describe how it structures human interactions, and highlight limitations of the official racial/ethnic categories enumerated by the US Office of Management and Budget.

Unmixing for race making in Brazil

This article analyzes race-targeted policy in Brazil as both a political stake and a powerful instrument in an unfolding classificatory struggle over the definition of racial boundaries. The Brazilian state traditionally embraced mixed-race classification, but is adopting racial quotas employing a black/white scheme. To explore potential consequences of that turn for beneficiary identification and boundary formation, the author analyzes attitudinal survey data on race-targeted policy and racial classification in multiple formats, including classification in comparison to photographs. The results show that almost half of the mixed-race sample, when constrained to dichotomous classification, opts for whiteness, a majority rejects mixed-race individuals for quotas, and the mention of quotas for blacks in a split-ballot experiment nearly doubles the percentage choosing that racial category. Theories of how states make race emphasize the use of official categories to legislate exclusion. In contrast, analysis of the Brazilian case illuminates how states may also make race through policies of official inclusion.

The categorization of African descent populations in Europe and the USA: should lexicons of recommended terminology be evidence-based?

This review attempts to evaluate a proposed lexicon for African-descent populations from the viewpoint of saliency amongst those described and wider official and scientific usage, focusing on Britain and the USA. It is argued that it is unsatisfactory to privilege the term 'African American' over 'Black' for African-descent populations in the USA as the evidence base shows that both labels compete as self-designations on co-equal terms, while 'Black' is the prevalent term in scientific writing. Moreover, 'African American' is not an inclusive term for the African-descent population and it is not known how prevalent and enduring the term will prove to be. With respect to Britain, the census terms of 'Black African' and 'Black Caribbean' are well established, the increasing popularity of 'Black British' also being recognized in census labels. Given the increasing interest in the relationship between ethnic identity and health, there are arguments for documenting the diversity of terminology amongst different user constituencies in country-specific settings. The approach of synthetic glossaries of consensual terms may, through the need for economy and parsimony in the use of terminology, contribute to an unsatisfactory paring of that diversity.

On classifying race in Brazil: example from a study of the functional ability of older people (60+)

How should race be categorized? This article investigates the usefulness of having three categories to describe a black-white racial continuum, focusing on Brazil and the functional ability of elderly (60+) people there. Ironically, even as the U.S. census has started to acknowledge mixed race again, much social research in Brazil has begun not to. Using 1998 national household survey microdata (PNAD) for Brazil, we find it advantageous to use a three-category scheme that separates a mixed black-white (pardo) status from black or white when examining the functional ability of elders. We also find the tantalizing possibility of a crossover in which browns actually have more functional ability than white counterparts after controlling for many demographic, geographic, and socioeconomic factors.

Cladistic analysis of Bantu languages: a new tree based on combined lexical and grammatical data

The phylogeny of the Bantu languages is reconstructed by application of the cladistic methodology to the combined lexical and grammatical data (87 languages, 144 characters). A maximum parsimony tree and Bayesian analysis supported some previously recognized clades, e.g., that of eastern and southern Bantu languages. Moreover, the results revealed that Bantu languages south and east of the equatorial forest are probably monophyletic. It suggests an unorthodox scenario of Bantu expansion including (after initial radiation in their homelands and neighboring territories) just a single passage through rainforest areas followed by a subsequent divergence into major clades. The likely localization of this divergence is in the area west of the Great Lakes. It conforms to the view that demographic expansion and dispersal throughout the dry-forests and savanna regions of subequatorial Africa was associated with the acquisition of new technologies (iron metallurgy and grain cultivation).

[In times of racialization: the case of the 'health of the black population' in Brazil]

The article analyzes initiatives aimed at creating a field of reflection and political intervention called the 'health of the black population,' which occurred between 1996 and 2004, that is, under the administration of Fernando Henrique Cardoso and part of Luis Inácio Lula da Silva's administration. During this period, the process of discussing and enacting affirmative action policies in Brazil gained greater visibility, especially following the UN-sponsored Third World Conference on Racism, Racial Discrimination, Xenophobia, and Related Intolerance (Durban, South Africa, September, 2001). The article describes the emergence of a proposal of compensatory policy within the Brazilian public health system. It then addresses the contemporary debate on race and health, especially the U.S. biomedical literature, and explores how this discussion has been appropriated by agencies and agents concerned with drawing up a 'racial policy' for the public health sector in Brazil.

Improving Identification of Hispanic Males in Medicare

OBJECTIVES

Medicare administrative and claims files maintained by the Centers for Medicare and Medicaid Services (CMS) are frequently used to examine racial and ethnic disparities in healthcare use. However, identification of Hispanic ethnicity for beneficiaries in the Medicare claims files is problematic, greatly limiting the use of these administrative data for examining race/ethnicity differences. This article reports on 2 studies assessing the effectiveness of a Hispanic surname match for improving the accuracy of race/ethnicity codes for elderly males in the Medicare data sets.

METHODS

Study 1 used survey data to compare a Medicare race code + Spanish surname composite indicator to self-identification as Hispanic. Study 2 used Medicare administrative files and U.S. Census 2000 data to identify how well the Medicare race code alone and the Medicare race code + Spanish surname composite indicator compared with estimates obtained from census data for 16 U.S. counties dispersed across 5 states.

RESULTS

Using self-identification as the gold standard, including the Spanish surname match increased accuracy for Hispanics and whites compared with the Medicare race code alone. The Spanish surname match also dramatically improved the Medicare code's estimation of elderly Hispanic and white males compared with county-level census data.

CONCLUSIONS

Augmenting the Medicare race code with a match to Spanish surnames yields substantial improvement in the identification of elderly Hispanic and white non-Hispanic male Medicare beneficiaries. Using surname information to supplement the Medicare race code could greatly enhance researchers' ability to examine healthcare equity.

Variation in the cranial base orientation and facial skeleton in dry skulls sampled from three major populations

The aim of this study was to analyse the effects of cranial base orientation on the morphology of the craniofacial system in human populations. Three geographically distant populations from Europe (72), Africa (48) and Asia (24) were chosen. Five angular and two linear variables from the cranial base component and six angular and six linear variables from the facial component based on two reference lines of the vertical posterior maxillary and Frankfort horizontal planes were measured. The European sample presented dolichofacial individuals with a larger face height and a smaller face depth derived from a raised cranial base and facial cranium orientation which tended to be similar to the Asian sample. The African sample presented brachyfacial individuals with a reduced face height and a larger face depth as a result of a lowered cranial base and facial cranium orientation. The Asian sample presented dolichofacial individuals with a larger face height and depth due to a raised cranial base and facial cranium orientation. The findings of this study suggest that cranial base orientation and posterior cranial base length appear to be valid discriminating factors between different human populations.

The Neolithic transition in Europe and North Africa. The functional craneology contribution

The origin and mode of the process that led to food production in Europe and North Africa is a matter intensively discussed. It is not clear in the transition to the Neolithic in these regions if it results by a migration of peoples from the Near East, by changes in the behaviour of local populations, or by an interaction of both processes. Morphological changes in Europe and North Africa, from the Upper Palaeolithic to modern periods were assessed. A method based on the Functional Matrix Hypothesis was carried out, which implies that the bone shape is modified by the related soft tissues. Absolute and relative size and shape changes were estimated on two major--neural and facial--and eight minor--anteroneural, midneural, posteroneural, otic, optic, respiratory, masticatory and alveolar--functional cranial components (FCC). ANOVA and Canonical Correlation analyses indicate that neither a temporal trend nor a pattern characteristic of each region is evidenced. But a shift is observed between the Upper Palaeolithic groups and the later samples. Size is greater in the Upper Palaeolithics. Shape is modified because Upper Palaeolithics have greater midneural and masticatory FCCs, and smaller optic FCC. The greater masticatory volume is associated to wider faces in hunter-gatherers. Our study cannot enable to conclude if the morphological shift is caused by a replacement or by a change in the local populations, however, the morphological changes can be attributed to the reduced mobility and the masticatory stress since the Neolithic period.

Genetic Ancestry Tracing and the African Identity: A Double-Edged Sword?

As both a geneticist and a Nigerian living in the United States, the author responds to the prospect of African Americans using genetic science to trace their ancestry to the African continent. He articulates concerns about both the limitations of the science to offer satisfying, accurate, and meaningful results, and the ability of individuals to make real, life-altering sense of these results. However, he notes that given the history and impact of slavery on African Americans, the desire to trace roots to Africa is both real and understandable.

Breast cancer research among African-American women: accurate racial categories?

This essay questions the appropriateness of racial categories in breast cancer research and recommends the discontinuation of "African-American" as a valid racial category in breast cancer research until better categories can be developed.

Single-nucleotide polymorphisms in the interleukin-10 gene: differences in frequencies, linkage disequilibrium patterns, and haplotypes in three United States ethnic groups

Interleukin-10 (IL-10) is a cytokine that seems to function as a downregulator of the innate (nonadaptive) immune system. Approximately three-quarters of interindividual variability in human IL-10 levels has been attributed to genetic variation, and there is evidence suggesting a potential role for IL-10 in a range of human diseases. To provide a basis for haplotype analysis and future disease association studies, we characterized genetic variation in IL10 by sequencing all exons, and 2.5 kb of the 5'- and the 3'-flanking region in a panel of DNA samples from 24 African Americans, 23 European Americans, and 24 Hispanic Americans. The region sequenced was found to contain 28 single-nucleotide polymorphisms (SNPs), 16 with frequency >2% and 14 with frequency >5%. All SNPs with frequency >5% were present in subjects from all three populations. No SNP caused amino acid changes. Differences in pairwise linkage-disequilibrium (LD) patterns and in SNP and haplotype frequency distributions among the three populations may be of potential importance for disease association studies.

Racial effects on neuropsychological functioning in schizophrenia

OBJECTIVE

This study assessed the effects of race on neuropsychological functioning in patients with schizophrenia.

METHOD

A total of 160 patients with schizophrenia completed an extensive neuropsychological test battery. Scores were standardized to a group of 99 psychiatrically and physically healthy subjects and categorized into seven functional domains: concentration, executive function, language, motor function, spatial memory, verbal memory, and visual processing.

RESULTS

African Americans (N=25) had significantly lower mean scores on executive function, language, spatial memory, and visual processing than did Caucasians (N=135). Statistical control for patient and family education eliminated all significant effects.

CONCLUSIONS

Educational differences in patients and families may account for some of the performance heterogeneity reported in patients with schizophrenia and should be routinely analyzed with other sociodemographic factors such as race and sex.

Race/ethnicity and the 2000 census: recommendations for African American and other black populations in the United States

This commentary considers the implications of the assessment of racial/ethnic status for monitoring the health of African Americans and other Black populations in the United States. It argues that because racial disparities in health and other social indicators persist undiminished, the continued assessment of race is essential. However, efforts must be made to ensure that racial data are of the highest quality. This will require uniform assessment of racial status that includes identifiers for subgroups of the Black population. Research also indicates that the health of multiracial persons varies by maternal race. Thus, efforts to monitor multiracial status should assess the race of both parents. More attention should also be given to analysis and interpretation of racial data and to the collection of additional data that capture characteristics linked to race (such as socioeconomic factors and racism) that may adversely affect health.

A new method for discriminating African-American from European-American skeletons using postcranial osteometrics reflective of body shape

A discriminant function analysis based on seven postcranial measurements for the metric assessment of race is presented. A sample from the Terry Collection (NMNH) was used to create independent functions for African-American males and females, and European-American males and females. The functions were tested using known forensic cases from the Maxwell Museum of Anthropology and the C.A. Pound Human Identification Laboratory. Based on the Terry Collection sample, correct classification of race for males was 87.0%, and for females 100.0%. For the independent test population, correct classification for males was 81.8%, and for females only 57.1%. The low classification for females is most likely due to sample bias.

Morphological variation in cervical spinous processes: potential applications in the forensic identification of race from the skeleton

Determination of race (ancestry) is an important step in the identification of individuals in forensic cases. Race is most commonly assessed using cranial traits. Few reliable postcranial indicators are known. In this study, the frequency of bifidity of cervical spinous processes at different vertebral levels was examined in a sample of 359 Americans of African (black) and European (white) descent. The sample was selected from the Hamann-Todd collection, a large modern anatomical collection of known sex and race. Spinous processes were classified as "bifid," "partially bifid," or "nonbifid" based on previously defined criteria. Sex and race were kept entirely unknown to the classifier (S.M.D.) during data collection. Data were analyzed using Chi-square and logistic regression analysis. At C2, most individuals (91%) had bifid spinous processes. At C7, nearly all (98%) had nonbifid spinous processes. Significant differences between race/sex subgroups were found at C3-C6. At each of these levels, whites showed a higher frequency of bifidity than blacks and males a higher frequency of bifidity than females. Differences between races were greater than differences within races. Logistic regression analysis revealed C3 and C4 to be the most useful levels for identifying race. Based on these levels, 76.05% of a validation subsample was correctly classified by race (80.25% for whites, 72.09% for blacks). Pending further study, morphology of the cervical spinous processes may provide an additional method for the determination of race in skeletal forensic cases.

Estimating African American admixture proportions by use of population-specific alleles

We analyzed the European genetic contribution to 10 populations of African descent in the United States (Maywood, Illinois; Detroit; New York; Philadelphia; Pittsburgh; Baltimore; Charleston, South Carolina; New Orleans; and Houston) and in Jamaica, using nine autosomal DNA markers. These markers either are population-specific or show frequency differences >45% between the parental populations and are thus especially informative for admixture. European genetic ancestry ranged from 6.8% (Jamaica) to 22.5% (New Orleans). The unique utility of these markers is reflected in the low variance associated with these admixture estimates (SEM 1.3%-2.7%). We also estimated the male and female European contribution to African Americans, on the basis of informative mtDNA (haplogroups H and L) and Y Alu polymorphic markers. Results indicate a sex-biased gene flow from Europeans, the male contribution being substantially greater than the female contribution. mtDNA haplogroups analysis shows no evidence of a significant maternal Amerindian contribution to any of the 10 populations. We detected significant nonrandom association between two markers located 22 cM apart (FY-null and AT3), most likely due to admixture linkage disequilibrium created in the interbreeding of the two parental populations. The strength of this association and the substantial genetic distance between FY and AT3 emphasize the importance of admixed populations as a useful resource for mapping traits with different prevalence in two parental populations.

The use of the supero-inferior femoral neck diameter as a sex assessor

The present study examines the sexing potential of the minimum supero-inferior femoral neck diameter in Caucasians and African-Americans who lived at the turn of the century. A Student's t-test and an ANOVA indicate that population differences in neck morphology exist, albeit the strength of the test is fairly weak (P = 0.015). Predictive models were developed using a linear discriminant function analysis for the African-American sample, the Caucasian sample, and the combined African-American and Caucasian (AAC) sample. Jackknifed classification matrices produced classification success rates ranging from 87 to 92%. Each of the three discriminant functions were evaluated using an independent, random holdout sample. Although a smaller holdout sample usually better approximates the true error involved in an application, this was clearly not the case in this study. For African-Americans, 28 of 28 individuals were correctly classified, for Caucasians 24 of 25, and for the combined AAC sample 53 of 53 individuals were sexed correctly. It is more likely that the true accuracy of the model for the population approximates 90%. This accuracy combined with the high rate of preservation of the femoral neck makes this measurement useful in extremely fragmentary samples.

A pilot study using the first cervical vertebra as an indicator of race

The articular surfaces and vertebral foramen of the first cervical vertebra can be used to estimate race from complete and fragmentary specimens. Eight measurements taken from 200 vertebrae from the Terry and Hamann-Todd collections (Smithsonian Institution and Cleveland Museum of Natural History, respectively) were used to construct 13 discriminant functions that predict race with 76-60% accuracy.

Sex estimation from the metatarsals

Discriminant-function analysis of osteometric data from the metatarsals of 200 individuals in the Terry Collection provides a reliable method for estimating sex. Functions derived from individual metatarsals and from complete sets of metatarsals are tested on the sample used to generate the functions and on two independent samples: one comprising 25 additional individuals from the Terry Collection and the other comprising 12 cadavers donated to the University of Missouri, Functions based on race-specific samples (blacks and whites) and on the pooled-race sample correctly classify 83 to 100% of each sample (including a jackknifed study sample), with a few exceptions. These results are similar to sex-estimation methods from other regions of the appendicular skeleton.

Southern Africa and modern human origins

This paper argues that southern Africa was a remote part of the Old World in the late Pleistocene (125- 10 ka ago). Because of this isolated position there was continuity without significant replacement in the resident population. Isolation and the relatively recent spread of agriculture to the region has allowed a section of this population to survive into the present. They are the Bushmen (San). Studies of geographic patterning in conventional genetic markers and mitochrondrial DNA indicate that the Bushman clade has a long evolutionary history in southern Africa. Estimates of more than 100 ka for the continued presence of this population in the region are supported in archaeological investigations of sites with long sequences such as Klasies River main site and Border Cave. Human remains dating to the earlier part of the late Pleistocene have been recovered from these sites and the samples form a morphological series with the Klasies River remains possibly 20 ka older than those from Border Cave. There is no fossil record for the later Pleistocene, however, at a period when selection for a gracile morphology may have been pronounced. The cultural associations in the earlier late Pleistocene are with the Middle Stone Age. Expressions of cultural ‘style’ and the occurrence of similar artefact design types in the Middle and Eater Stone Ages can be interpreted with reference to the ethnographic present. Temporal continuity can be shown in the geographical distribution of stylistic markers and this suggests participation in a shared cognitive system. The inference is that the people in the earlier late Pleistocene had cognitive abilities that are comparable to those shown by their Holocene and modern descendants. The presence of the ancestors of a modern population in the earlier late Pleistocene in this region is perhaps expected if modern people had their origins in Africa.

Allometry and adaptation of body proportions and stature in African pygmies

We have analyzed the growth allometry of external body proportions in Efe pygmies from Zaire and combined these data with values from the literature for comparable dimensions in adult pygmies and nonpygmies. We sequentially tested the hypotheses that adult proportion differences between 1) male vs. female Efe, and 2) pygmies vs. nonpygmies result from ontogenetic scaling, or the differential extension of common patterns of growth allometry. Results indicate an almost complete concordance of allometric trajectories for male and female Efe. These preliminary analyses also strongly suggest that adult nonpygmy Africans generally differ from pygmies in their terminal size and correlated allometric consequences, rather than in more fundamental alterations of underlying patterns of growth. Biacromial diameter emerges as the measurement most likely to depart from this general pattern. These results provide further evidence that shifts in systemic growth hormones yielding differences in terminal overall body size may be accompanied by global and coordinated allometric transformations. Certain proportion differences previously interpreted by some as specific evidence of primitive retention in pygmies in fact reflect simple growth allometric correlates of the derive rapid size decrease in these groups. Selected divergent body proportions characterizing adult pygmies, previously interpreted by some as independent evidence of climatic adaptation, also reflect such allometric correlates of ontogenetic scaling. We critically assess arguments that the small overall body size of pygmies was specifically selected for reasons of thermoregulatory efficiency, and consider an alternative or complementary scenario, based on selection for small size in order to reduce caloric requirements.

Racial characteristics of human teeth with special emphasis on the Mongoloid dentition

Determining the racial affinity of an unknown individual from dentition for identification is indeed a difficult endeavour. However, there are certain dental characteristics which are predominant in certain racial groups and these contribute important indicators in the identification process. Inherited dental characteristics are modified by prenatal and postnatal environmental and nutritional conditions. They can also become less discernible due to admixture of the various races.

Excess admixture proportion of extended major histocompatability complex haplotypes of Caucasian origin among rheumatoid arthritis associated haplotypes in African Americans and Afro-Caribbeans

Several extended major histocompatability complex (MHC) haplotypes are associated with susceptibility to autoimmune disease in Caucasian populations. It is known that African Americans and Afro-Caribbeans are ethnic groups descended from west, central and southern black African populations which are admixed with Caucasians. To examine the possible association of some marker of Caucasian MHC genes and susceptibility to rheumatoid arthritis (RA) in African Americans, we studied extended MHC haplotypes (HLA-B, complement and DR) in a sample of 18 African American and Afro-Caribbean probands with RA, their first degree relatives and in 15 non-RA families. We defined 36 disease-associated RA haplotypes among the probands and 96 normal haplotypes in normal individuals. To obtain the most conservative estimate, we excluded recognized Caucasian, DR4-bearing, extended MHC haplotypes from the analysis. Admixture proportions for non-HLA-DR4 extended MHC haplotypes of known Caucasian origin among RA-associated and normal haplotypes were computed (0.40 versus 0.163 respectively). When we compared the difference in proportions between RA and normal haplotypes, the proportion of extended MHC haplotypes of known Caucasian origin was significantly increased among RA-associated haplotypes (Z = 3.16, p (one sided) < 0.001, p (adjusted) < 0.008). Our results suggest that racial admixture with Caucasian MHC genes may augment RA susceptibility and thus may be one mechanism to explain the higher prevalence of RA in African Americans and Afro-Caribbeans than in black African populations.

Anatomical and profile analysis of the female black American nose

An anatomical and anthropometric study was conducted that compared nasal pyramid measurements of Negroid with Caucasian skulls and surface measurements of black with Caucasian controls. Eight external surface measurements were used to develop a classification system to show the range of the female black American nose. This classification will be described along with the range of measurements on which it is based. This classification may provide a better understanding of the anatomic characteristics of the normal variation of Negroid noses, and thus improve the surgeon's ability to evaluate black patients for rhinoplasty.

Allocation and discrimination based on human odontometric data

This study contrasts the confidence with which individuals may be grouped and then re-allocated on the basis of odontometric data. These data are derived from the mesiodistal and buccolingual diameters of 202 Lengua Indians of Paraguay (100 males, 102 females), 125 Caucasoid schoolchildren (59 male, 66 female), and 206 Negroes (106 male, 100 female). Multivariate intergroup discrimination is effected by means of canonical and stepwise discriminant analysis, whilst allocation is evaluated by means of posterior and typicality probabilities. Bias is reduced by means of a jackknifing procedure. High levels of discriminatory confidence (each Wilk's Lambda, P less than 0.01) are matched by high percentage correct classification (Caucasoid, 67.4-75.0%; Negro, 71.0-77.3%; Amerindian, 65.2-78.1%). However, these results are not matched by allocatory procedures: only 21.7% of caucasoids, 21.4% of Negroes, and 28.8% of Amerindians could be re-allocated with probabilities in excess of 80%. It is concluded that while multivariate discriminant techniques may be usefully employed in the separation of different populations, individuals may not be assigned with the same degree of confidence, even with an a priori knowledge of their group membership.