Race, Genetic Ancestry, and Health: A Direction for Anthropological Genetics in the 2010′s?

Batai, K. and R. A. Kittles (2013). “Race, Genetic Ancestry, and Health.” Race and Social Problems 5(2): 81-87.

In June 2013 edition of Race and Social Problems journal, we published this review article.  I think, for anthropologists who have a training in genetics, it is an interesting direction that we should explore more.  When I was almost done with my dissertation work, I began to think what I could do after I got my degree.  I was dissatisfied with anthropological genetics.  Although I was excited to investigate human genetic variation and evolution and had fun learning and teaching (I am still interesting in these topic and continue to explore), I felt “so what?”  I understand the importance of understanding migration history and genetic variation in the world, but I felt that anthropologists and many people, mostly wealthy people, are interested in human past and variation mostly only for their intellectual interests.  Who really care about our findings?  Are they really useful knowledge?

Then, I began thinking about using anthropological perspectives and methods to help other people.  I contacted my current mentor, Dr. Rick Kittles, to see if I could do genetic research on health disparities.  I learnt genetic epidemiology, a study of roles of genetics in determining or influencing disease risk in families or populations.  In the genetic epidemiology, a lot of population genetics knowledge and methods are applied to the basic epidemiological research design.  More recently, genetic epidemiologists are showing interests in gene and environment interactions.  Here, environment refers to lifestyle and socio-cultural factors.  Gene and environmental interactions is basically what anthropologists call “bio-cultural perspective,” but genetic epidemiologists think more statistically.

In the U.S., we see a great racial health disparities.  Differences in access to health care and health screen can explain a part of health disparities, but there are more complex, genetic, biological, and socio-cultural factors that are intertwined with ‘race.’  Anthropologists are trained to understand this complex relationship.  We can bring different insights in the genetic research of health disparities from scientists who were trained in other fields, and we can contribute to biomedical science in unique ways.

Social and cultural factors are better predictors of blood pressure in African Americans more than genetic ancestry

The association between genetic ancestry and skin color has been well demonstrated (see here).  The heritability of skin color is quite high suggesting that contribution of genetic components to skin color is high as well.  Many genetic research projects support this showing that variants in pigmentation candidate genes are associated with skin color or other pigmentation traits (reviewed here).  However, it is often difficult to demonstrate the association between genetic ancestry and common diseases because social-cultural factors (socio-economic status, education, income, employment status, access to health care, etc.) confound the relationship.

The association between skin color and blood pressure among African Americans has been investigated by many researchers (see here), but more recently researchers started using genetic ancestry estimates to test the association between African ancestry and blood pressure.  In genetic studies, information on only clinically relevant variables are collected, so association between genetic ancestry and disease phenotype (here blood pressure) is often tested without adjusting for socio-cultural and environmental factors.  Only a few studies conducted so far examined 1) effects of genetic ancestry and socio-cultural factors simultaneously and 2) interactions of these factors.

Non et al. (2012) explored the association between genetic ancestry and blood pressure and between education and blood pressure using publically available Family Blood Pressure Program (FBPP) study data.  They found that education, not genetic ancestry, was significantly associated with blood pressure in African Americans and interaction between education and race also plays a role in the racial difference in blood pressure.

First, they examined if African ancestry estimated using 294 autosomal STR was a predictor of blood pressure in African Americans.  They did not observe significant difference in African ancestry between hypertensive and non-hypertensive African Americans.  In the linear regression model, education was significantly associated with blood pressure but African ancestry was not.  They did not observe interaction between African ancestry and education either.

Second, they examined if education explains difference in blood pressure between African Americans and European Americans.  African Americans with high-school degree or who did not complete high-school degree have significantly higher blood pressure than people with higher educations.  They did not observe the same pattern in European American, however.  In the regression analysis, they observed the interaction between education and race.  In addition, they showed that decline in SBP is sharper with increasing educational levels in African Americans than in European Americans.

This is an interesting study to show that education (and probably poverty), not genetic ancestry, is a very important factor affecting blood pressure in African American, suggesting that obtaining higher education will benefit African Americans more than European Americans.  As noted by the authors, one of the limitations of this study is that education was only social-environmental factor available in the dataset and they used it as a proxy for socio-economic status and other social environmental factors.  While I agree that education can be very useful for capturing the many social-environmental factors and their analyses clearly show that socio-environmental factors measured with education are very important predictors or risk factors of blood pressure in African Americans, African American societies are too diverse and heterogeneous, and there should be many socio-environmental factors that affect blood pressure but not captured with education.  They also could explore more what socio-economic factors were captured with education.

It is interesting to note that anthropologically trained scientists are showing that socio-cultural factors are as important as genetic factors assessed with genetic ancestry estimates and skin color.  In other papers, Gravlee at al. (2005 and 2009) have shown that skin color or genetic ancestry is associated with blood pressure in Puerto Ricans, but social classification based on skin color is associated with blood pressure in Puerto Ricans.  They also observed statistically significant interaction between skin color and socio-economic status.

References:

Gravlee, C. C., W. W. Dressler, et al. (2005). “Skin Color, social classification, and blood pressure in Southeastern Puerto Rico.” Am J Public Health 95(12): 2191-2197.

Gravlee, C. C., A. L. Non, et al. (2009). “Genetic ancestry, social classification, and racial inequalities in blood pressure in Southeastern Puerto Rico.” PLoS ONE 4(9): e6821.

Non, A. L., C. C. Gravlee, et al. (2012). “Education, genetic ancestry, and blood pressure in African Americans and Whites.” Am J Public Health 102(8): 1559-1565.

 

Is skin color associated with blood pressure in African Americans?

Anthropologists have been interested in evolution of skin color for a long time, but I believe that anthropologists and other scientists should study about it for many reasons.  Here is one of many reasons.

Boyle (1970) and others observed association between skin color and high blood pressure among African Americans long time ago, and in these studies, skin color was used as a proxy for admixture and Africa ancestry.  However, subsequent studies demonstrated complex relationship between skin color, socioeconomic status, and blood pressure.

For example, Klag et al. (1991) observed the association between skin color and blood pressure in African Americans, and they showed that darker-skinned African Americans tend to have increased blood pressure.  They also show that this association depends on the socioeconomic status.  Among African Americans in the lowest socioeconomic status, darker-skinned African Americans had considerably higher blood pressure level than lighter-skinned African Americans, but they did not observe the same pattern among the African Americans in the higher socioeconomic status.  In their multivariate regression analysis, they observed significant interaction between skin color and socioeconomic status associated only with diastolic blood pressure.  Moreover, they showed that whether African Americans completed high school education or not had a significant effect on blood pressure and again they observed statistically significant interaction between skin color and education (please note that survey data was collected between 1972-1974).

More recent study by Sweet et al. (2007) reported similar findings.  They also found that darker-skinned African Americans have higher blood pressure in the CARDIA study, and they found the significant interaction between skin color and income.  In a similar study of blood pressure, Gravlee at al. (2005) have shown that skin color is not associated with blood pressure in Puerto Ricans, but social classification based on skin color is associated with blood pressure in Puerto Ricans.

These studies show that both genetic/biological factors and socio-environmental factors have a great impact on blood pressure in African Americans.  The effects of both of these factors on blood pressure, and maybe on other disease phenotypes, should be examined simultaneously.

References;

Boyle, E., Jr. (1970). “Biological patterns in hypertension by race, sex, body weight, and skin color.” JAMA: The Journal of the American Medical Association 213(10): 1637-1643.

Gravlee, C. C., W. W. Dressler, et al. (2005). “Skin Color, social classification, and blood pressure in Southeastern Puerto Rico.” Am J Public Health 95(12): 2191-2197.

Klag, M. J., P. K. Whelton, et al. (1991). “The association of skin color with blood pressure in us blacks with low socioeconomic status.” JAMA 265(5): 599-602.

Sweet, E., T. W. McDade, et al. (2007). “Relationships between skin color, income, and blood pressure among African Americans in the CARDIA study.” Am J Public Health 97(12): 2253-2259.

Genes associated with human pigmentation traits in Genome-Wide Association Studies (GWAS)

Although there are many issues, Genome-Wide association study (GWAS) has been a powerful method to identify genetic variants associated with phenotypic traits.  GWAS is generally used to find genetic variants associated with disease, but it also found variants associated with anthropometric traits, such as height and BMI.  Also, there are several GWAS mainly among people of European descents aiming to find genetic variants associated with pigmentation characteristics (hair, eye, and skin color, freckles, and skin sensitivity to sun or tanning ability) (e.g., Eriksson, 2010; Han, 2008; Kayser, 2008; Liu, 2010; Nan, 2009; Sulem, 2008; Sulem, 2007)   These GWAS identified variants associated with pigmentation characteristics on SLC45A2 (Chr5), IRF4 (Chr6), TYRP1 (Chr9), TYR (Chr11), KITLG (Chr12), SLC24A4 (Chr14), OCA2/HERC2 (Chr15), MC1R (Chr16), and ASIP (Chr20).  These studies showed very strong association of variants in these genes with hair color, eye color, freckles, sensitivity to the sun, and tanning ability.

However, because the skin color does not vary much in European populations, these GWAS were not very successful showing the association between genetic variants and skin pigmentation, and only one of these studies, in which people of non-European descents were included, successfully showed the association between skin color and an IRF4 variant (Han et al. 2008).

Another GWAS among South Asians demonstrated the association of skin color with variants in two genes (SLC45A2 and TYR), but the study also found that another gene, SLC24A5 (Chr15) is associated with skin color (Stokowski et al. 2007).  The association of SLC24A5 variants with skin color in African Americans has been reported previously (Lamason et al. 2005).  More recently, Kenny et al. report that an amino acid change in TYRP1 associated with blond hair among Solomon Islanders (Kenny, 2012).

Identifying these genetic variants is important not only to understand major human phenotypic variation and the mechanism of evolution of pigmentation traits, but also to find variants that may be associated with skin cancer and to understand the risk factors for vitamin D deficiency.  Because of admixture, African Americans exhibit a great range of skin color, so they are desirable for genetic study of skin pigmentation.

Eriksson, N., J. M. Macpherson, et al. (2010). “Web-Based, Participant-Driven Studies Yield Novel Genetic Associations for Common Traits.” PLoS Genet 6(6): e1000993.

Han, J., P. Kraft, et al. (2008). “A Genome-Wide Association Study Identifies Novel Alleles Associated with Hair Color and Skin Pigmentation.” PLoS Genet 4(5): e1000074.

Kayser, M., F. Liu, et al. (2008). “Three Genome-wide Association Studies and a Linkage Analysis Identify HERC2 as a Human Iris Color Gene.” American Journal of Human Genetics 82(2): 411-423

Kenny, E. E., N. J. Timpson, et al. (2012). “Melanesian Blond Hair Is Caused by an Amino Acid Change in TYRP1.” Science (New York, N.Y.) 336(6081): 554.

Lamason, R. L., M. A. Mohideen, et al. (2005). “SLC24A5, a putative cation exchanger, affects pigmentation in zebrafish and humans.” Science (New York, N.Y.) 310(5755): 1782-1786.

Liu, F., A. Wollstein, et al. (2010). “Digital Quantification of Human Eye Color Highlights Genetic Association of Three New Loci.” PLoS Genet 6(5): e1000934.

Nan, H., P. Kraft, et al. (2009). “Genome-Wide Association Study of Tanning Phenotype in a Population of European Ancestry.” J Invest Dermatol 129(9): 2250-2257.

Stokowski, R. P., P. V. K. Pant, et al. (2007). “A Genomewide Association Study of Skin Pigmentation in a South Asian Population.” American Journal of Human Genetics 81(6): 1119-1132.

Sulem, P., D. F. Gudbjartsson, et al. (2008). “Two newly identified genetic determinants of pigmentation in Europeans.” Nat Genet 40(7): 835-837.

Sulem, P., D. F. Gudbjartsson, et al. (2007). “Genetic determinants of hair, eye and skin pigmentation in Europeans.” Nat Genet 39(12): 1443-1452.

TYR and OCA2: two genes associated with skin pigmentation in African Americans

Shriver, M. D., E. J. Parra, et al. (2003). “Skin pigmentation, biogeographical ancestry and admixture mapping.” Human Genetics 112(4): 387-399.

Previously, I wrote about correlation between West African Ancestry (WAA) estimates and skin color among African Americans and African Caribbeans (here).  They used 33 ancestry informative markers (AIMs) that have large frequency differences between African and European populations.  Three of these markers are candidate genes for skin pigmentation (TYR, OCA2, and MC1R), so they examined, if these skin color candidate genes are associated with skin color (Melanin Index measure using the DermaSpectrometer).

Two pigmentation candidate genes (TYR and OCA2) and many other AIMs were associated with M Index without adjusting for WAA.  When they adjust for WAA, only TYR remained significant.  Then, they used ADMIXMAP, admixture mapping software, to find segments of genome that are associated with skin pigmentation because of the differences in their genetic ancestry.  In this analysis, TYR and OCA2 are associated with skin color, but not MC1R.

Their analyses demonstrated that two pigmentation candidate genes (TYR and OCA2) likely to cause differences in skin color between African and European populations.  TYR produces an enzyme, tyrosinase, which catalyzes the first two reactions in the melanin synthesis pathway.  Mutations in OCA2, or P gene, cause the common type of albinism.

I hope to review follow-up research projects later to further understand genes involved in production of dark skin in African and African American populations.

Geneticists tend to overemphasize the importance of genetic factors for resolving the ethnic health disparities

Sankar, P., M. K. Cho, et al. (2004). “Genetic Research and Health Disparities.” JAMA: The Journal of the American Medical Association 291(24): 2985-2989.

We (geneticists, media, students, etc) tend to focus on the genetic aspects of research and overemphasize on the importance o f genes on human evolution, health, etc.  As an anthropologist, I tried to be careful about it and I tried to consider socio-cultural aspects as well, but I admit that I often focus on genetic aspects more than socio-cultural aspects.  In this article, Shankar et al (2004) argue that overemphasizing genetic factors in ethnic health disparities research can have negative impacts.

Although they are well aware of many factors causing ethnic health disparities, researchers tend to overemphasize the potential benefits of their genetic research resolving the health disparities problems.  One of the reasons why geneticists overemphasize on genetic factor is their funding.  U.S. National Human Genome Research Institute (NHGRI) took an initiative to address the health disparities.  The negative consequence is that the attention shifts away from real social-cultural problems that need to addressed, but are difficult to fix, such as poverty, unequal access to health care, diet, etc.  Also, overemphasizing genetic factors may reinforce the racial rebelling and stereotyping.

It is true when we write grant proposals and papers, we have to say that our findings from genetic research can uniquely contribute to resolve the existing problems.  We do not mean to overemphasize, but it is important to note that research findings can be very important.  In addition, we scientists loose objectivity and tend to thick findings from our research project is so special.

The correlation and variability of African genetic ancestry and skin color among African Americans

Parra, E. J., R. A. Kittles, et al. (2004). “Implications of correlations between skin color and genetic ancestry for biomedical research.” Nature Genetics 36: S54-S60.

Shriver, M. D., E. J. Parra, et al. (2003). “Skin pigmentation, biogeographical ancestry and admixture mapping.” Human
Genetics 112(4): 387-399.

 

These articles are getting little old, but their findings are interesting and important.  They examined the correlation between skin pigmentation and estimated African ancestry.  Using a DermaSpectrometer, skin color measurements (melanin index) were taken inner part of arm where the UV rarely hit.  African genetic ancestry was estimated using 33 ancestry informative markers (AIMs).

They found that estimated African ancestry was significantly correlated with melanin index, as expected, but more interestingly melanin index and estimated African ancestry vary greatly.  This means that functional genes that determine the skin color are located somewhere else on the genome and the allele frequencies of these skin pigmentation gene variants differ greatly between ancestral populations (e.g., Africans and Europeans for African Americans).  They explain that because African Americans are recently admixed, we are observing the results of the population structure that existed in their ancestral populations.

Skin color is a very heritable trait.  If skin color is determined largely by genes, one may expect to see small variability of melanin index of African Americans with 100% African ancestry, but that is not the case.  They observed a great variation in melanin index of African Americans with 100% African ancestry.  Because skin color is polygenic traits, there are many different genes that determine the skin color, so natural variation in skin color should exist in Africa.

The research was conducted when only a few candidate genes linked to skin color were found, and they confirmed that two candidate genes for skin pigmentation, TYR and OCA2 are significantly associated with melanin index in African Americans (actually, Shriver and colleagues were working on other projects looking for skin color genes when these articles came
out).

How variable is the skin color and melanin index in Africa?  There are research projects that demonstrated that skin color varies among sub-Saharan African populations, but has anybody systematically investigated how variable the skin color is within an African population?

Genetic evidence of Indian Ocean slave trade from Indian Siddis

Shah, Anish M., R. Tamang, et al. (2011). “Indian Siddis: African Descendants with Indian Admixture.” American Journal of Human Genetics 89(1):154-161.

Compared to Tran-Atlantic slave trade, Indian Ocean Slave trade is less known, maybe less understood, but has longer history.  Indigenous Africans were captured and traded by other Africans, Arabs, and Europeans.  Some of the slaves were sent to Middle East and South Asia.  Sub-Saharan African mtDNA haplogroups have been found among the Middle Eastern populations and the frequencies range from 9 to 34%.  Sub-Saharan African Y chromosome haplogroups are rare, but are also found among the Middle Eastern Arab populations.  Richards et al. (2003) and Quintana-Murci et al. (2004) argue that these sub-Saharan African mtDNA haplogroups were brought to the Middle East and reached South Asian through the Arab slave trade.  African females were incorporated into Islamic societies, but African males did not have much chance of reproduction.

In this article, Shah et al. (2011) demonstrate that Siddis, or Habishis, from India, the descendants of slaves from Africa, have genetic characteristics of sub-Saharan Africans.  They genotyped 850,000 autosomal SNPs, 32 Y chromosome biallelic markers, and 17 Y chromosome STR and sequenced mtDNA hypervariable region I.

Among Siddis, sub-Saharan genetic contribution estimated based on autosomal SNPs is quite large ranging 62.3-74.4% and they are plotted more closely to HapMap Yorubans than Indians, Europeans, or Asians on the PC plot.  Contrary to the previous studies, they found more male sub-Saharan contribution to the Siddis than female contribution.  You could expect this from the Indians marriage rule of endogamy, but gene flow between the Siddis and neighboring ethnic groups or communities was unidirectional.  They found South Asians and Eurasian genetic
contribution to the Siddis from their neighboring communities, but they did not find Sub-Saharan genetic contribution from the Siddis to neighboring ethnic groups.

Genetic studies to understand slave trade are usually conducted using uniparental markers (mtDNA and Y-chromosome).  The molecular genetic and analytical techniques to trace the origin are relatively simple, but the problem is that you are tracing only two lineages (maternal and paternal) out of thousands of possible ancestors for a particular individual.  By analyzing autosomal markers, you are getting genetic information of all the ancestors.  Recent advancement in molecular genetics allows researchers to genotypes many single nucleotide polymorphisms (SNPs) per individual.  Sometime in the future, it will be possible to genotype over 1 million SNPs per individual without huge cost.  Down side of this is that it requires more sophisticated statistical and analytical techniques.

References:

Quintana-Murci L, Chaix R, Wells S, Behar DM, Sayar H, Scozzari R, Rengo C, Al-Zaheri N, Semino O, Santachiara-Benerecetti AS, Coppa A, Ayub Q, Mohyuddin A, Tyler-Smith C, Mehdi SQ, Torroni A, and McElreavey K (2004) Where west meets east: the complex mtDNA landscape of southwest and Central Asian corridor. American Journal of Human Genetics 74:827-845.

Richards M, Rengo C, Cruciani F, Gratrix F, Wilson JF, Scozzari R, Macaulay V, and Torroni A (2003) Extensive female-mediated gene flow from Sub-Saharan Africa into Near Eastern Arab Populaitons. American Journal of Human Genetics 72:1058-1064.

A support for vitamin D hypothesis of skin color evolution?: a correlation between African genetic ancestry and blood vitamin D concentration

Signorello, L. B., S. M. Williams, et al. (2010). “Blood Vitamin D Levels in Relation to Genetic Estimation of African Ancestry.” Cancer Epidemiology Biomarkers & Prevention 19(9): 2325-2331.

Anthropologists have been hypothesizing the evolutionary relationship between skin color and  vitamin D (reviews are here and here), but the mechanism of evolution has not been explained well.  Lately, I have been reading about genetic determinants of vitamin D concentration in the blood and implication for health, especially among African Americans.  In this post, I am reviewing an interesting article investigating the relationship between genes and serum vitamin D level.

Signorello et al. (2010) investigated if the differences in vitamin D concentration in the blood between African Americans and European Americans are influenced by genetic variation by examining the correlation between serum vitamin D and estimated African ancestry, and they demonstrated that serum vitamin D concentration was inversely correlated with genetic estimation of West African Ancestry.  They recruited 379 African Americans and 379 European Americans from 12 southeastern U.S. states.  They used 300 ancestry informative markers (AIMs) and estimated African and European ancestry using STRUCTURE.

They found that the estimated west African ancestry among European Americans was low ranging from 0.001 to 0.171 (mean, 0.009) (note there is no genetically pure European).  The estimated west African ancestry varied more among African Americans ranging from 0.505 to 0.999 (mean, 0.929).  Serum vitamin D concentration was lower for the African Americans than European Americans, and the lowest in the African Americans with higher estimation of west African ancestry, even after adjusting for age, sex, average daily dietary intake of vitamin D, mean residential UV radiation score, BMI, employment, smoking, alcohol intake, and education level.

This study does not show if any particular genes are involved influencing the serum vitamin D level.  However, they used the genetic ancestry, not skin color or self-identified racial identity, as a proxy for underlying genetic background, and they demonstrated that there should be genetic basis for the differences in serum vitamin D level between African Americans and Europeans Americans.  From an anthropological and evolutionary perspective, it is important to address the relationship between vitamin D level and skin pigmentation considering underlying genetic factors, but they did not investigate the relationship or they did not use skin color measurement to statistically adjust the serum vitamin D concentration.

UPDATE

I have been thinking about how these kinds of genetic research, examining the correlation between African genetic ancestry estimates and phenotypes (including disease related traits), should be done.  One of the major issues seems to be combining African Americans and European Americans in the same analysis.  African ancestry estimates among the African Americans tend to range widely with high estimates, while European Americans have very low African ancestry and do not have much variation.  If the distribution of African ancestry estimates is shown on the graph, there should be two non-overlapping peaks, one wide peak for African Americans and one narrow peak for European Americans.  Implication of uneven distributions in these analyses has not been discussed in this article or other similar articles.

Persistence of racial thinking in the online communities

There are arguments on Afrocentrism, Eurocentrism, and criticisms against these ethnocentrisms in the online communities, such as blogs and YouTube.  For example, some argue whether ancient Egyptians were black Africans or not, while others question if the first Europeans looked more like modern Africans or not.  Despite anthropologists, geneticists, and educators’ efforts to eradicate racial thinking among the public, I believe that these arguments exist because of persistence of racial, or typological thinking among the human population geneticists as well as the public.

Keita and Kittles (1997) argue that racial thinking, not racist thinking, persists in the studies of human evolution through use of phylogenetic trees to show evolutionary relationship of human groups and by estimating divergence time between major racial groups(e.g. Cavalli-Sforza et al., 1994; Nei and Roychoudhury, 1993).  Weiss and Long (2009) also argue that some human geneticists have replaced ‘old racial classification’ with more sophisticated scientific methods identifying human population clusters using multilocus genetic data and Structure-like population genetics methods (e.g. Rosenberg et al., 2002; Li et al., 2008). 

One underlying assumption that racial thinking and clustering approach is based on is relative reproductive isolation because of lack of gene flow (e.g., Andreasen, 2004; Cavalli-Sforza et al., 1994; Risch et al., 2002).  People, including human geneticists, with racial thinking believe that human populations have had very limited gene flow, where there are geographic barriers and linguistic, cultural, and political differences.  They also focus on biological, genetic, linguistic, and cultural differences between different groups, while assuming that there are genetic, cultural, and linguistic similarities within a human group.

However, many anthropologists and human geneticists believe that gene flow between different human groups is common and there are great biological, genetic, cultural, and linguistic variations even within small human populations (e.g., American Association of Physical Anthropologists statement on race; Livingston, 1962; Tishkoff et al., 2009).  Therefore, the clusters that human geneticists identified should not be equated with racial groups. 

So, where did the ideas of Black Africans, Europeans, Asians…. come from?  These ideas were developed based on stereotypes of people living in different parts of the world, probably very recently, after the colonial era (American Anthropological Association statement on race).  Ancient Egyptians and the first Europeans probably did not have self-identities as Africans, Caucasians, or Europeans.  Ancient Egypt was multi-ethnic state. 

Note: This also posted on the blog section of AnthroGenetics website.

Reference

American Anthropological Association Statement on Race

American Association of Physical Anthropologists – AAPA Statement on Biological Aspects of Race

Andreasen, R. O. (2004). “The cladistic race concept: a defense.” Biology and Philosophy 19: 425-442.

Cavalli-Sforza, L. L., R. Menozzi, et al. (1994). The History and Geography of Human Genes. Princeton, NJ, Princeton University Press.

Keita, S. O. Y. and R. A. Kittles (1997). “The persistence of racial thinking and the myth of racial divergence.” American Anthropologist 99: 534-544.

Li, J. Z., D. M. Absher, et al. (2008). “Worldwide Human Relationships Inferred from Genome-Wide Patterns of Variation.” Science 319(5866): 1100-1104.

Livingstone, F. B. (1962). “On the non-existence of human races.” Current Anthropology 3: 279-281.

Nei, M. and A. K. Roychoudhury (1993). “Evolutionary relationships of human populations on a global scale.” Molecular Biology and Evolution 10(5): 927-943.

Risch, N., E. Burchard, et al. (2002). “Categorization of humans in biomedical research: genes, race and disease.” Genome Biology 3(7): comment2007.2001-2007.2012.

Rosenberg, N. A., J. K. Pritchard, et al. (2002). “Genetic Structure of Human Populations.” Science 298(5602): 2381-2385.

Tishkoff, S. A., F. A. Reed, et al. (2009). “The Genetic Structure and History of Africans and African Americans.” Science 324(5930): 1035-1044.

Weiss, K. M. and J. C. Long (2009). “Non-Darwinian estimation: My ancestors, my genes’ ancestors.”Genome Research 19(5): 703-710.