African American populations in the U.S. formed primarily by mating between Africans and Europeans over the last 500 years.

Posted in Excerpts/Quotes on 2018-02-13 03:29Z by Steven

African American populations in the U.S. formed primarily by mating between Africans and Europeans over the last 500 years.

Jessica M. Gross, “Tests of fit of historically-informed models of African American Admixture,” American Journal of Physical Anthropology, (Volume 165), Issue 2, February 2018, 211. https://dx.doi.org/10.1002/ajpa.23343.

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Tests of fit of historically-informed models of African American Admixture

Posted in Anthropology, Articles, Health/Medicine/Genetics, Media Archive, United States on 2018-02-13 01:49Z by Steven

Tests of fit of historically-informed models of African American Admixture

American Journal of Physical Anthropology
Volume 165, Issue 2, February 2018
Pages 211–222
DOI: 10.1002/ajpa.23343

Jessica M. Gross
Department of Anthropology
University of New Mexico

African American populations in the U.S. formed primarily by mating between Africans and Europeans over the last 500 years. To date, studies of admixture have focused on either a one-time admixture event or continuous input into the African American population from Europeans only. Our goal is to gain a better understanding of the admixture process by examining models that take into account (a) assortative mating by ancestry in the African American population, (b) continuous input from both Europeans and Africans, and (c) historically informed variation in the rate of African migration over time.

Materials and methods

We used a model-based clustering method to generate distributions of African ancestry in three samples comprised of 147 African Americans from two published sources. We used a log-likelihood method to examine the fit of four models to these distributions and used a log-likelihood ratio test to compare the relative fit of each model.

Results

The mean ancestry estimates for our datasets of 77% African/23% European to 83% African/17% European ancestry are consistent with previous studies. We find admixture models that incorporate continuous gene flow from Europeans fit significantly better than one-time event models, and that a model involving continuous gene flow from Africans and Europeans fits better than one with continuous gene flow from Europeans only for two samples. Importantly, models that involve continuous input from Africans necessitate a higher level of gene flow from Europeans than previously reported.

Discussion

We demonstrate that models that take into account information about the rate of African migration over the past 500 years fit observed patterns of African ancestry better than alternative models. Our approach will enrich our understanding of the admixture process in extant and past populations.

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AAPA Statement on Biological Aspects of Race

Posted in Anthropology, Health/Medicine/Genetics, Statements on 2014-11-09 21:27Z by Steven

AAPA Statement on Biological Aspects of Race

American Journal of Physical Anthropology
Volume 101, Issue 4, December 1996
pages 569–570
DOI: 10.1002/ajpa.1331010408

PREAMBLE

As scientists who study human evolution and variation, we believe that we have an obligation to share with other scientists and the general public our current understanding of the structure of human variation from a biological perspective. Popular conceptualizations of race are derived from 19th and early 20th century scientific formulations. These old racial categories were based on externally visible traits, primarily skin color, features of the face, and the shape and size of the head and body, and the underlying skeleton. They were often imbued with nonbiological attributes, based on social constructions of race. These categories of race are rooted in the scientific traditions of the 19th century, and in even earlier philosophical traditions which presumed that immutable visible traits can predict the measure of all other traits in an individual or a population. Such notions have often been used to support racist doctrines. Yet old racial concepts persist as social conventions that foster institutional discrimination. The expression of prejudice may or may not undermine material well-being, but it does involve the mistreatment of people and thus it often is psychologically distressing and socially damaging. Scientists should try to keep the results of their research from being used in a biased way that would serve discriminatory ends.

POSITION

We offer the following points as revisions of the 1964 UNESCO statement on race:

  1. All humans living today belong to a single species, Homo sapiens, and share a common descent. Although there are differences of opinion regarding how and where different human groups diverged or fused to form new ones from a common ancestral group, all living populations in each of the earth’s geographic areas have evolved from that ancestral group over the same amount of time. Much of the biological variation among populations involves modest degrees of variation in the frequency of shared traits. Human populations have at times been isolated, but have never genetically diverged enough to produce any biological barriers to mating between members of different populations.
  2. Biological differences between human beings reflect both hereditary factors and the influence of natural and social environments. In most cases, these differences are due to the interaction of both. The degree to which environment or heredity affects any particular trait varies greatly.
  3. There is great genetic diversity within all human populations. Pure races, in the sense of genetically homogenous populations, do not exist in the human species today, nor is there any evidence that they have ever existed in the past

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African ancestry of the population of Buenos Aires

Posted in Anthropology, Articles, Caribbean/Latin America, Media Archive on 2013-06-21 03:29Z by Steven

African ancestry of the population of Buenos Aires

American Journal of Physical Anthropology
Volume 128, Issue 1
pages 164–170, September 2005
DOI: 10.1002/ajpa.20083

Laura Fejerman
Institute of Biological Anthropology
University of Oxford

Francisco R. Carnese
Sección Antropología Biológica
Instituto de Ciencias Antropológicas
Facultad de Filosofía y Letras
Universidad de Buenos Aires

Alicia S. Goicoechea
Sección Antropología Biológica
Instituto de Ciencias Antropológicas
Facultad de Filosofía y Letras
Universidad de Buenos Aires

Sergio A. Avena
Sección Antropología Biológica
Instituto de Ciencias Antropológicas
Facultad de Filosofía y Letras
Universidad de Buenos Aires

Cristina B. Dejean
Sección Antropología Biológica
Instituto de Ciencias Antropológicas
Facultad de Filosofía y Letras
Universidad de Buenos Aires

Ryk H. Ward (1943-2003)
Institute of Biological Anthropology
University of Oxford

The population of Argentina today does not have a “visible” black African component. However, censuses conducted during most of the 19th century registered up to 30% of individuals of African origin living in Buenos Aires city. What has happened to this African influence? Have all individuals of African origin died, as lay people believe? Or is it possible that admixture with the European immigrants made the African influence “invisible?” We investigated the African contribution to the genetic pool of the population of Buenos Aires, Argentina, typing 12 unlinked autosomal DNA markers in a sample of 90 individuals. The results of this analysis suggest that 2.2% (SEM = 0.9%) of the genetic ancestry of the Buenos Aires population is derived from Africa. Our analysis of individual admixture shows that those alleles that have a high frequency in populations of African origin tend to concentrate among 8 individuals in our sample. Therefore, although the admixture estimate is relatively low, the actual proportion of individuals with at least some African influence is approximately 10%. The evidence we are presenting of African ancestry is consistent with the known historical events that led to the drastic reduction of the Afro-Argentine population during the second half of the 19th century. However, as our results suggest, this reduction did not mean a total disappearance of African genes from the genetic pool of the Buenos Aires population.

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A quantitative method of morphological assessment of hybridization in the U. S. Negro-White male crania

Posted in Anthropology, Articles, Media Archive, United States on 2012-08-31 01:16Z by Steven

A quantitative method of morphological assessment of hybridization in the U. S. Negro-White male crania

American Journal of Physical Anthropology
Volume 41, Issue 2 (September 1974)
pages 269–278
DOI: 10.1002/ajpa.1330410209

Sudha S. Saksena
Department of Sociology and Anthropology
Muskingum College [Muskingum University], New Concord, Ohio

Portions of this paper are based on a doctoral dissertation submitted to the University of Indiana, Bloomington, Indiana, in 1967. Part of this paper appeared in abstract form in American Journal of Physical Anthropology, Vol. 29, No. 1, 1968, pp. 124–125.

The study develops a morphological method of assessing the amount of parental components in a U.S. Negro-White Hybrid sample and tests to what extent a multivariate discriminant analysis actually reflects the morphological pattern of hybridization.

To formulate norms of description for the parental and hybrid populations, a seventeenth century London Farringdon Street series of 94 crania was selected to represent the British White ancestral component and the data on the cadaverand-skeletal series in the T. W. Todd collection of Western Reserve University, Cleveland, Ohio, were used in the selection of 115 Unmixed Negro and 115 Negro-White Hybrid male crania.

The conclusions are: (1) the morphological scores of the Negro-White Hybrid series shows a biological overlap with the two parental series in the proportion of 1:3 (i.e., 25% White to 75% Negro). This overlap reflects the probable porportion of ancestral mixture in the ratio of one-fourth White to three-fourths Negro in the Negro-White Hybrid sample; and (2) the morphological approach to the assessment of the parental components with multivariate discriminant analysis as a tool, proves to be highly reliable in providing a biologically meaningful index of relationship.

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Effects of interracial crosses on cephalometric measurements

Posted in Anthropology, Articles, Media Archive, United States on 2012-08-24 20:43Z by Steven

Effects of interracial crosses on cephalometric measurements

American Journal of Physical Anthropology
Volume 69, Issue 4 (April 1986)
pages 465–472
DOI: 10.1002/ajpa.1330690405

C. S. Chung
Department of Public Health Sciences
University of Hawaii, Manoa

D. W. Runck
Department of Public Health Sciences
University of Hawaii, Manoa

S. E. Bilben
Department of Public Health Sciences
University of Hawaii, Manoa

M. C. W. Kau
Division of Dental Health
Hawaii State Department of Health

The effects of race and interracial crossing were examined on six cephalometric measurements among 9, 912 schoolchildren in Hawaii. The measurements studied were face height, bizygomatic diameter, bigonial diameter, head breadth, head length, and cephalic index. Racial effects were studied in terms of general racial effect, maternal effect, and hybridity and recombination effects based on a model of diallel cross. Generally, Chinese, Japanese, Koreans, and Filipinos were characterized by longer lateral and smaller anterior-posterior dimensions relative to Caucasians. Maternal effects appeared to be present in the measures of lateral dimension. No clear effects of hybridity and recombination were seen except for bizygomatic diameter, which appears to behave as a partial dominant trait. The racial mean of bizygomatic diameter, or the ratio of this measure to head length, were found to have a relationship with the racial incidences of cleft lip with or without cleft palate.

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The Founder Effect and Deleterious Genes

Posted in Anthropology, Articles, Health/Medicine/Genetics, History, Media Archive, Tri-Racial Isolates, United States on 2012-03-16 02:35Z by Steven

The Founder Effect and Deleterious Genes

American Journal of Physical Anthropology
Volume 30, Issue 1 (January 1969)
pages 55-60
DOI: 10.1002/ajpa.1330300107

Frank B. Livingstone (1928-2005), Professor Emeritus of Biological Anthropology
University of Michigan

During the rapid growth of a population from a few founders, a single deleterious gene in a founder can attain an appreciable frequency in later generations. A computer simulation, which has the population double itself in early generations, indicates a lethal could attain a frequency of 0.1. Since deleterious recessive genes are eliminated from large populations at a very slow rate, variations in their frequencies in present major human populations may be due to the founder effect during earlier rapid expansion.

Many distinctive human populations are characterized by the presence of one or more lethal or severely deleterious genes in frequencies which would be defined as polymorphic according to Ford’s (’40) famous definition. The particular genetic disorder, however, varies. The Old Order Amish of Lancaster County, Pennsylvania have a gene frequency of 0.07 for the recessive Ellis-van Creveld syndrome, while the Amish as a whole have a frequency of about 0.05 of the recessive cartilage-hair hypoplasia syndrome ( McKusick et al., ’64). Many of the tri-racial isolates of Eastern United States also have a high frequency of a deleterious gene (Witkop et al., ’66). Although such populations are frequently defined by religious or ethnic criteria, there are others not so defined. Several island populations in the Åland archipelago have a gene frequency of greater than 0.1 for von Willebrand’s disease (Eriksson, ’61), and the Boer population of South Africa and some populations of Northern Sweden have frequencies of porphyria much greater than those of other populations (Dean, ’63; Waldenstrom and Haeger-Aronsen, ’67). However, these conditions are dominant and do not have the very severe effects of other hereditary disorders found in high frequencies. On the other hand the population of the Chicoutimi District of Quebec has recently been found to have a gene frequency of about 0.02 for tyrosinemia, which is a lethal recessive (Laberge and Dallaire, ’67).

In most of these cases the population in question has undergone a rapid increase in recent years, and the question arises as to whether this rapid expansion and the original small size of the isolate could account for the high frequency of the deleterious gene. Such an explanation by the founder effect seems obviously to apply to most of the cases cited above, but the founder effect may well be a more general explanation of human gene frequency differences. It is now becoming apparent that the major populations of mankind vary significantly in their frequencies of deleterious genes and that many large populations such as Eastern European Jews have high frequencies of deleterious genes which are found in low frequencies in other populations McKusick, ’66). There have been many attempts to determine how such genes could be polymorphic, for example, Anderson et al. (’67) and Knudson et al. (’67) have discussed cystic fibrosis and Myrianthopoulos and Aronson (’66), Tay-Sachs disease. The purpose of this paper is to attempt to determine the extent to which the founder effect can cause high frequencies of deleterious genes with various models of population expansion.

The occurrence which initiated this research is the gene for sickle cell hemoglobin in the Brandywine isolate of Southeast Maryland. At present the sickle cell gene frequency in this isolate is about 0.1 (Rucknagel, ’64). The high frequencies of this gene in many parts of Africa, India, and the Middle East are now well-accepted as being due to a relative resistance of the sickle cell heterozygote to falciparum malaria. The high frequency in the Brandywine isolate may have a similar explanation, but the surrounding Negro population does not have such a high frequency. And although the endemicity of falciparum malaria in Southeast Maryland in the last century is not known in any detail, it would not appear to have been great enough to explain the high sickle cell frequency in the Brandywine isolate. The isolate also has many other deleterious genes in high frequency (Witkop et al., ’66).

The Brandywine isolate seems to have had its beginning in the early Eighteenth Century when laws were passed to prohibit co-habitation and marriage among races, which prior to then were presumably frequent or at least known. Up to 1720 there were several prosecutions under these laws of individuals with surnames currently present in the isolate (Harte, ’63). Harte (’63) has maintained that the Brandywine isolate is derived from these illegal unions, and Witkop et al. (‘66) show that the most common surname came from such a union. In 1790 the first United States Census recorded 190 persons with the group’s surnames as “other free people,” and since then over 90% of the recorded marriages have been endogamous or between individuals with surnames within the group (Harte, ’59). According to Harte (’59) there are six “core” surnames which have been associated with the group since its founding and comprise 66% of the population and another ten surnames which entered the group after the Civil War, but Witkop et al. (‘66) list seven core surnames and eight marginal ones. The total population of the isolate is now estimated to be 5,128 (Witkop et al., ’66), and the statistics do indicate rapid, if erratic, growth (Gilbert, ’45; Harte, ’63)…

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Race and global patterns of phenotypic variation

Posted in Anthropology, Articles, Media Archive on 2012-03-03 21:38Z by Steven

Race and global patterns of phenotypic variation

American Journal of Physical Anthropology
Volume 139, Issue 1 (May 2009) Special Issue: Race Reconciled: How Biological Anthropologists View Human Variation
pages 16–22
DOI: 10.1002/ajpa.20900

John H. Relethford, Distinguished Teaching Professor of Anthropology
State University of New York, Oneonta

Phenotypic traits have been used for centuries for the purpose of racial classification. Developments in quantitative population genetics have allowed global comparison of patterns of phenotypic variation with patterns of variation in classical genetic markers and DNA markers. Human skin color shows a high degree of variation among geographic regions, typical of traits that show extensive natural selection. Even given this high level of geographic differentiation, skin color variation is clinal and is not well described by discrete racial categories. Craniometric traits show a level of among-region differentiation comparable to genetic markers, with high levels of variation within populations as well as a correlation between phenotypic and geographic distance. Craniometric variation is geographically structured, allowing high levels of classification accuracy when comparing crania from different parts of the world. Nonetheless, the boundaries in global variation are not abrupt and do not fit a strict view of the race concept; the number of races and the cutoffs used to define them are arbitrary. The race concept is at best a crude first-order approximation to the geographically structured phenotypic variation in the human species.

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The Seminole Indians of Florida: Morphology and Serology

Posted in Anthropology, Articles, Health/Medicine/Genetics, History, Native Americans/First Nation, United States on 2012-01-18 00:43Z by Steven

The Seminole Indians of Florida: Morphology and Serology

American Journal of Physical Anthropology
Volume 32, Number 1 (January, 1970)
pages 65-81

William S. Pollitzer
University of North Carolina, Chapel Hill

Donald L. Rucknagel
University of Michigan

Richard E. Tashian
University of Michigan

Donald C. Shreffler
University of Michigan

Webster C. Leyshon
National Institute of Dental Research, NIH

Kadambari Namboodiri
Carolina Population Center
University of North Carolina

Robert C. Elston
University of North Carolina

The Seminole Indians of Florida were studied on their three reservations for blood types, red cell enzymes, serum proteins, physical measurements, and relationships. Both serologic and morphologic factors suggest their close similarity to other Indians and small amount of admixture. The Florida Seminoles are similar to Cherokee “full-bloods” in their absence of Rho and their incidence of O and M. In the presence of Dia they are similar to other Indians, especially those of South America. While the presence of G-6-P-D A and the frequency of Hgb. S are indicative of Negro ancestry, the absence of Rho suggests that the Negro contribution must have been small. Physical traits give parallel results. Both serology and morphology further show that the Seminoles of the Dania and Big Cypress reservations are more similar to each other than to those of the Brighton reservation, in keeping with their history.

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Biohistorical approaches to “race” in the United States: Biological distances among African Americans, European Americans, and their ancestors

Posted in Anthropology, Articles, Media Archive, United States on 2011-04-26 22:11Z by Steven

Biohistorical approaches to “race” in the United States: Biological distances among African Americans, European Americans, and their ancestors

American Journal of Physical Anthropology
Special Issue: Race Reconciled: How Biological Anthropologists View Human Variation
Volume 139, Issue 1 (May 2009)
pages 58-67
DOI: 10.1002/ajpa.20961

Heather J.H. Edgar, Research Assistant Professor of Anthropology and Curator of Human Osteology, Maxwell Museum of Anthropology
University of New Mexico, Albuquerque

Author’s: Note: This study explores the effects of cultural concepts of race on changes in subpopulations in the United States. While some aspects of biology may correlate with cultural constructions of race, use of the term “race” here does not imply its biological validity under any definition. When not otherwise indicated, the words “race” or “racial” are used in this article to describe social categories.

Folk taxonomies of race are the categorizations used by people in their everyday judgments concerning the persons around them. As cultural traditions, folk taxonomies may shape gene flow so that it is unequal among groups sharing geography. The history of the United States is one of disparate people being brought together from around the globe, and provides a natural experiment for exploring the relationship between culture and gene flow. The biohistories of African Americans and European Americans were compared to examine whether population histories are shaped by culture when geography and language are shared. Dental morphological data were used to indicate phenotypic similarity, allowing diachronic change through United States history to be considered. Samples represented contemporary and historic African Americans and European Americans and their West African and European ancestral populations (N = 1445). Modified Mahalanobis’ D2 and Mean Measure of Divergence statistics examined how biological distances change through time among the samples. Results suggest the social acceptance for mating between descendents of Western Europeans and Eastern and Southern European migrants to the United States produced relatively rapid gene flow between the groups. Although African Americans have been in the United States much longer than most Eastern and Southern Europeans, social barriers have been historically stronger between them and European Americans. These results indicate that gene flow is in part shaped by cultural factors such as folk taxonomies of race, and have implications for understanding contemporary human variation, relationships among prehistoric populations, and forensic anthropology.

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