Lessons from a "primitive" people

The Genes of Freedom: Genome-Wide Insights into Marronage, Admixture and Ethnogenesis in the Gulf of Guinea

The forced migration of millions of Africans during the Atlantic Slave Trade led to the emergence of new genetic and linguistic identities, thereby providing a unique opportunity to study the mechanisms giving rise to human biological and cultural variation. Here we focus on the archipelago of São Tomé and Príncipe in the Gulf of Guinea, which hosted one of the earliest plantation societies relying exclusively on slave labor. We analyze the genetic variation in 25 individuals from three communities who speak distinct creole languages (Forros, Principenses and Angolares), using genomic data from expanded exomes in combination with a contextual dataset from Europe and Africa, including newly generated data from 28 Bantu speakers from Angola. Our findings show that while all islanders display mixed contributions from the Gulf of Guinea and Angola, the Angolares are characterized by extreme genetic differentiation and inbreeding, consistent with an admixed maroon isolate. In line with a more prominent Bantu contribution to their creole language, we additionally found that a previously reported high-frequency Y-chromosome haplotype in the Angolares has a likely Angolan origin, suggesting that their genetic, linguistic and social characteristics were influenced by a small group of dominant men who achieved disproportionate reproductive success.

Evolutionary Models of Leadership : Tests and Synthesis

This study tested four theoretical models of leadership with data from the ethnographic record. The first was a game-theoretical model of leadership in collective actions, in which followers prefer and reward a leader who monitors and sanctions free-riders as group size increases. The second was the dominance model, in which dominant leaders threaten followers with physical or social harm. The third, the prestige model, suggests leaders with valued skills and expertise are chosen by followers who strive to emulate them. The fourth proposes that in small-scale, kin-based societies, men with high neural capital are best able to achieve and maintain positions of social influence (e.g., as headmen) and thereby often become polygynous and have more offspring than other men, which positively selects for greater neural capital. Using multiple search strategies we identified more than 1000 texts relevant to leadership in the Probability Sample of 60 cultures from the Human Relations Area Files (HRAF). We operationalized the model with variables and then coded all retrieved text records on the presence or absence of evidence for each of these 24 variables. We found mixed support for the collective action model, broad support for components of the prestige leadership style and the importance of neural capital and polygyny among leaders, but more limited support for the dominance leadership style. We found little evidence, however, of emulation of, or prestige-biased learning toward, leaders. We found that improving collective actions, having expertise, providing counsel, and being respected, having high neural capital, and being polygynous are common properties of leaders, which warrants a synthesis of the collective action, prestige, and neural capital and reproductive skew models. We sketch one such synthesis involving high-quality decision-making and other computational services.

Cultural Innovations Influence Patterns of Genetic Diversity in Northwestern Amazonia

Human populations often exhibit contrasting patterns of genetic diversity in the mtDNA and the nonrecombining portion of the Y-chromosome (NRY), which reflect sex-specific cultural behaviors and population histories. Here, we sequenced 2.3 Mb of the NRY from 284 individuals representing more than 30 Native American groups from Northwestern Amazonia (NWA) and compared these data to previously generated mtDNA genomes from the same groups, to investigate the impact of cultural practices on genetic diversity and gain new insights about NWA population history. Relevant cultural practices in NWA include postmarital residential rules and linguistic exogamy, a marital practice in which men are required to marry women speaking a different language. We identified 2,969 SNPs in the NRY sequences, only 925 of which were previously described. The NRY and mtDNA data showed different sex-specific demographic histories: female effective population size has been larger than that of males through time, which might reflect larger variance in male reproductive success. Both markers show an increase in lineage diversification beginning ∼5,000 years ago, which may reflect the intensification of agriculture, technological innovations, and the expansion of regional trade networks documented in the archaeological evidence. Furthermore, we find similar excesses of NRY versus mtDNA between-population divergence at both the local and continental scale, suggesting long-term stability of female versus male migration. We also find evidence of the impact of sociocultural practices on diversity patterns. Finally, our study highlights the importance of analyzing high-resolution mtDNA and NRY sequences to reconstruct demographic history, since this can differ considerably between sexes.

Neutral Theory: From Complex Population History to Natural Selection and Sociocultural Phenomena in Human Populations

Here, we present a synthetic view on how Kimura's Neutral theory has helped us gaining insight on the different evolutionary forces that shape human evolution. We put this perspective in the frame of recent emerging challenges: the use of whole genome data for reconstructing population histories, natural selection on complex polygenic traits, and integrating cultural processes in human evolution.

"An Unusual and Fast Disappearing Opportunity": Infectious Disease, Indigenous Populations, and New Biomedical Knowledge in Amazonia, 1960-1970

In the twentieth century, biomedical researchers believed the study of Indigenous Amazonians could inform global histories of human biological diversity. This paper examines the similarities and differences of two approaches to this mid-century biomedical research, comparing the work of virologist and epidemiologist Francis Black with human geneticists James V. Neel and Francisco Salzano. While both groups were interested in Indigenous populations as representatives of the past, their perspectives on epidemics diverged. For Black, outbreaks of infectious diseases were central to his methodological and theoretical interests; for Neel and Salzano, epidemics could potentially compromise the epistemological value of their data.

Indigenous Peoples, Postcolonial Contexts and Genomic Research in the Late 20th Century

In the 1960s the human geneticist James V. Neel and collaborators launched a research program aimed at investigating the human biology of South American indigenous populations, which would become one of the most influential such studies in the second half of the 20th century. In the first part of this article I explore the trajectory of some components of the Amazonian research program and situate it in the context of worldwide human biological research in the 1960s and 1970s. In the second half I suggest that the comparative analysis of previous research on the human biology of indigenous peoples might provide insights into highly debated issues pertaining to contemporaneous research agendas, including the `Human Genome Diversity Project' (HGDP).

Patrilineal populations show more male transmission of reproductive success than cognatic populations in Central Asia, which reduces their genetic diversity

OBJECTIVE

The extent to which social organization of human societies impacts the patterns of genetic diversity remains an open question. Here, we investigate the transmission of reproductive success in patrilineal and cognatic populations from Central Asia using a coalescent approach.

METHODS

We performed a study on the mitochondrial DNA (mtDNA) and Y chromosome polymorphism of patrilineal and cognatic populations from Central Asia. We reconstructed the gene genealogies in each population for both kind of markers and inferred the imbalance level of these genealogies, a parameter directly related to the level of transmission of reproductive success.

RESULTS

This imbalance level appeared much stronger for the Y chromosome in patrilineal populations than in cognatic populations, while no difference was found for mtDNA. Furthermore, we showed that this imbalance level correlates negatively with Y-chromosomal, mtDNA, and autosomal genetic diversity.

CONCLUSIONS

This shows that patrilineality might be one of the factors explaining the male transmission of reproductive success, which, in turn, lead to a reduction of genetic diversity. Thus, notwithstanding the fact that our population genetic approach clearly shows that there is a strong male-biased transmission of reproductive success in patrilineal societies, it also highlights the fact that a social process such as cultural transmission of reproductive success could play an important role in shaping human genetic diversity, although we cannot formally exclude that this transmission has also a genetic component.

Unfolding epidemiological stories: how the WHO made frozen blood into a flexible resource for the future

In the decades after World War II, the World Health Organization (WHO) played an important role in managing the process of stabilizing collections of variable blood samples as a fundamentally unstable, protean, and unfolding biomedical resource. In this system, known and as yet unknown constituents of blood were positioned as relevant to the work of multiple constituencies including human population geneticists, physical anthropologists, and immunologists. To facilitate serving these and other constituencies, it was crucial to standardize practices of collecting and preserving samples of blood from globally distributed human populations. The WHO achieved this by linking its administrative infrastructure-comprised of expert advisory groups and technical reports-to key laboratories, which served as sites for demonstrating and also for disseminating standards for working with variable blood samples. The practices that were articulated in making blood samples into a flexible resource contributes to emerging histories of global health that highlight the centrality of new institutions, like the WHO, new forms of expertise, like population genetics and serological epidemiology, and new kinds of research materials, like frozen blood.

Genome-wide association study identifies candidate genes for male fertility traits in humans

Despite the fact that hundreds of genes are known to affect fertility in animal models, relatively little is known about genes that influence natural fertility in humans. To broadly survey genes contributing to variation in male fertility, we conducted a genome-wide association study (GWAS) of two fertility traits (family size and birth rate) in 269 married men who are members of a founder population of European descent that proscribes contraception and has large family sizes. Associations between ∼250,000 autosomal SNPs and the fertility traits were examined. A total of 41 SNPs with p ≤ 1 × 10(-4) for either trait were taken forward to a validation study of 123 ethnically diverse men from Chicago who had previously undergone semen analyses. Nine (22%) of the SNPs associated with reduced fertility in the GWAS were also associated with one or more of the ten measures of reduced sperm quantity and/or function, yielding 27 associations with p values < 0.05 and seven with p values < 0.01 in the validation study. On the basis of 5,000 permutations of our data, the probabilities of observing this many or more small p values were 0.0014 and 5.6 × 10(-4), respectively. Among the nine associated loci, outstanding candidates for male fertility genes include USP8, an essential deubiquitinating enzyme that has a role in acrosome assembly; UBD and EPSTI1, which have potential roles in innate immunity; and LRRC32, which encodes a latent transforming growth factor β (TGF-β) receptor on regulatory T cells. We suggest that mutations in these genes that are more severe may account for some of the unexplained infertility (or subfertility) in the general population.

The Evolution of Human Longevity: Distinctive Mechanisms?

La durée de vie maximale (MLS [Maximum Life Span]) de l'homo sapiens est considérablement plus longue que celle de nos plus proches parents, notamment les primates non-humains. Puisque le mouvement évolutionniste depuis le primate commun ancestral est survenu relativement récemment, les changements génétiques agissant sur le MLS ont done dû également survenir rapidement. L'évolution du MLS s'explique généralement par un effet pleiotropique de substance génétique qui accélère ou renvoie à plus tard toute détérioration cellulaire. Cependant, chez les humains, la notion qu'il pourrait exister une sélection directe visant la longévité semble plausible: chez les hommes, par des mécanismes de santé physique personnelle et chez les femmes, une santé physique équilibrée. Le seul défaut évident retrouvé dans cette ligne de raisonnement est qu'elle est non-falsifiable.

Claude Lévi-Strauss on Race, History, and Genetics

In 1952, the French anthropologist Claude Lévi-Strauss published a small booklet titled Race and History. It formed part of a series of pamphlets on the so-called "race-question" by leading anthropologists and geneticists, which UNESCO published as part of its campaign against racism. Roughly twenty years later, in 1971, UNESCO invited Lévi-Strauss to give a lecture to open the International Year of Action to Combat Racism and Racial Discrimination. This time the lecture, titled "Race and culture," caused a scandal. In 2005, on occasion of the Organisation's 60th anniversary, Lévi-Strauss was once again invited by UNESCO to give a lecture. It followed the same lines as his 1971 speech, but now met with acclaim. In my paper I will analyze Lévi-Strauss' interventions with respect to their reliance on contemporary genetics. Lévi-Strauss always saw a close analogy between structuralist anthropology and genetics, and derived his anti-evolutionary stance from the combinatory logic that both disciplines endorsed. I will argue, that it was this combinatory logic which created room for historical contingency and agency in Lévi-Strauss' understanding of the history of humankind.

Colloquium papers: Heritability of reproductive fitness traits in a human population

The genetic basis of fitness traits has been studied widely in animals, yet the contribution of genetic variation to these traits in humans is controversial. In particular, it is difficult to disentangle genetic versus environmental effects on fertility, because of within-family correlations of sociocultural, economic, and other nongenetic factors that influence family sizes. In this study, we investigated the genetic architecture of reproductive fitness traits in a fertile human population whose communal lifestyle assures uniform and equal access to resources. Our study revealed significant heritabilities for reproductive traits in both men and women, after accounting for common household effects shared among siblings and demographic changes in reproductive practices. Furthermore, our results indicate that both autosomal and X-linked additive and dominance variances contribute to these traits. We therefore propose that reproductive traits should be amenable to genetic mapping studies, and the results we present here will facilitate the search for the novel genes influencing natural fertility in humans.

Eugenics from the New Deal to the Great Society: genetics, demography and population quality

The relationship between biological and social scientists as regards the study of human traits and behavior has often been perceived in terms of mutual distrust, even antipathy. In the interwar period, population study seemed an area that might allow for closer relations between them-united as they were by a concern to improve the eugenic quality of populations. Yet these relations were in tension: by the early post-war era, social demographers were denigrating the contributions of biologists to the study of population problems as embodying the elitist ideology of eugenics. In response to this loss of credibility, the eugenics movement pursued a simultaneous program of withdrawal and expansion: its leaders helped focus concern with biological quality onto the developing field of medical genetics, while at the same moment, extended their scope to improving the social quality of populations through birth control policies, guided by demography. While this approach maintained boundaries between the social and the biological, in the 1960s, a revitalized American Eugenics Society helped reunite leading demographers and geneticists. This paper will assess the reasons for this period of influence for eugenics, and explore its implications for the social and biological study of human populations.

Sex-specific genetic structure and social organization in Central Asia: insights from a multi-locus study

In the last two decades, mitochondrial DNA (mtDNA) and the non-recombining portion of the Y chromosome (NRY) have been extensively used in order to measure the maternally and paternally inherited genetic structure of human populations, and to infer sex-specific demography and history. Most studies converge towards the notion that among populations, women are genetically less structured than men. This has been mainly explained by a higher migration rate of women, due to patrilocality, a tendency for men to stay in their birthplace while women move to their husband's house. Yet, since population differentiation depends upon the product of the effective number of individuals within each deme and the migration rate among demes, differences in male and female effective numbers and sex-biased dispersal have confounding effects on the comparison of genetic structure as measured by uniparentally inherited markers. In this study, we develop a new multi-locus approach to analyze jointly autosomal and X-linked markers in order to aid the understanding of sex-specific contributions to population differentiation. We show that in patrilineal herder groups of Central Asia, in contrast to bilineal agriculturalists, the effective number of women is higher than that of men. We interpret this result, which could not be obtained by the analysis of mtDNA and NRY alone, as the consequence of the social organization of patrilineal populations, in which genetically related men (but not women) tend to cluster together. This study suggests that differences in sex-specific migration rates may not be the only cause of contrasting male and female differentiation in humans, and that differences in effective numbers do matter.

Health and disease in unacculturated Amerindian populations

The stereotype of uncontacted tribal populations is that they must reproduce at near capacity to maintain or slightly increase their numbers. This paper argues that the health of minimally contacted Amerindians, as judged by the results of physical examinations and life tables for the Yanomama of Southern Venezuela and Northern Brazil, is relatively good, with population control a feature of the Indian culture. It is further argued that the usual deterioration in health with contacts with western culture probably does not result so much from special innate susceptibilities to certain epidemic diseases and to the diets and 'stresses' of civilization as from the epidemiological characteristics of newly contacted peoples.

Some characteristics of tribal peoples

The study of health and disease in distinctive human groups is an important source of knowledge, and ultimately of understanding. Tribal societies are at the polar extreme from modernized communities. However, with the breakdown of isolation this distinctiveness is being eroded, slowly for genes, more rapidly for ideas and behaviour, and fastest for infective agents of disease. Though comtemporary tribal men cannot be equated with prehistoric men, they resemble them more than do modernized men. Therefore the study of tribal peoples not only widens the range of circumstances in which human adaptability is observed, it throws some light on the evolution of human diseases. This is particularly the case with regard to the study of 'diseases of modern life'. Tribal life is characterized by comparative physical and cultural isolation, simplicity, small group size, low population density and closeness to nature, both physically and conceptually. In spite of rapid change, which itself needs study, there are still situations where what is studied has shown little recent change. In a world where dissatisfaction with life and medicine grows in spite of unparalleled technical success, we should look again at tribal men. There is much to learn from each other's successes and failures.

Chronic problems in understanding tribal violence and warfare

This paper discusses problems confronting researchers whose work addresses the nature, causes and functions of violence and warfare in contemporary tribal societies and the interpretation of evidence on these topics from archaeological records. A major problem is the paucity of reliable ethnographic evidence describing conflicts, causes of conflicts and numbers of casualties suffered. There are few first-hand studies of warring tribesmen and little uniformity in data collection methods or specific topics covered by the studies. A second problem is the wide range of theoretical opinion on ultimate versus proximate causes of conflict and often polemic insistence that some causes cannot even be admitted into the explanatory framework, as illustrated by the debate between cultural materialists and evolutionary anthropologists. A third problem is the widespread belief that pre-colonial conflict and warfare was either rare or did not exist at all and that where contemporary tribesmen are found to be in lethal contests this has been provoked by contact with European colonial expansion. Finally, a new problem is emerging: ethnographic descriptions of violence in tribal societies are increasingly opposed by politically correct academics who argue that it is detrimental to the goals of advocates of native cultural survival. The paper concludes with a summary of some of the main features of Yanomamö violence and warfare, based on the author's field research and publications up to 1990, and introduces new data and theoretical issues that are emerging from his most recent field studies since 1990.

Correlation of intergenerational family sizes suggests a genetic component of reproductive fitness

Reproductive fitness is a complex phenotype that is a direct measure of Darwinian selection. Estimation of the genetic contribution to this phenotype in human populations is confounded by within-family correlations of sociocultural, economic, and other nongenetic factors that influence family sizes. Here, we report an intergenerational correlation in reproductive success in the Hutterites, a human population that is relatively homogeneous with respect to sociocultural factors that influence fertility. We introduce an estimator of this correlation that takes into account the presence of multiple parent-offspring pairs from the same nuclear family. Statistical significance of the estimated correlation is assessed by a permutation test that maintains the overall structure of the pedigree. Further, temporal trends in fertility within this population are accounted for. Applying these methods to the S-Leut Hutterites yields a correlation in effective family size of 0.29 between couples and their sons and 0.18 between couples and their daughters, with empirical P<1x10-6 and P=.0041, respectively. Similar results were obtained for completed families (0.31 between couples and their sons and 0.23 between couples and their daughters; empirical P<1x10-6 and P=.00059, respectively). We interpret these results as indicating a significant genetic component to reproductive fitness in the Hutterites.

Genetic studies of stuttering in a founder population

Genome-wide linkage and association analyses were conducted to identify genetic determinants of stuttering in a founder population in which 48 individuals affected with stuttering are connected in a single 232-person genealogy. A novel approach was devised to account for all necessary relationships to enable multipoint linkage analysis. Regions with nominal evidence for linkage were found on chromosomes 3 (P=0.013, 208.8 centiMorgans (cM)), 13 (P=0.012, 52.6 cM), and 15 (P=0.02, 100 cM). Regions with nominal evidence for association with stuttering that overlapped with a linkage signal are located on chromosomes 3 (P=0.0047, 195 cM), 9 (P=0.0067, 46.5 cM), and 13 (P=0.0055, 52.6 cM). We also conducted the first meta-analysis for stuttering using results from linkage studies in the Hutterites and The Illinois International Genetics of Stuttering Project and identified regions with nominal evidence for linkage on chromosomes 2 (P=0.013, 180-195 cM) and 5 (P=0.0051, 105-120 cM; P=0.015, 120-135 cM). None of the linkage signals detected in the Hutterite sample alone, or in the meta-analysis, meet genome-wide criteria for significance, although some of the stronger signals overlap linkage mapping signals previously reported for other speech and language disorders.

EDUCATIONAL OBJECTIVES

After reading this article, the reader will be able to: (1) summarize information about the background of common disorders and methodology of genetic studies; (2) evaluate the role of genetics in stuttering; (3) discuss the value of using founder populations in genetic studies; (4) articulate the importance of combining several studies in a meta-analysis; (5) discuss the overlap of genetic signals identified in stuttering with other speech and language disorders.

Albinism (OCA2) in Amerindians

Homozygosity for a mutation in the P locus mapped to the human chromosome 15q11.2-12 results in tyrosinase-positive albinism (OCA2). This type of albinism has a worldwide distribution, with a prevalence of about 1 in 36,000 among European-Americans in the United States. It has a moderate to relatively high prevalence values (1 in 28 to 1 in 6,500) in various Amerindian populations in the southwestern United States, southern Mexico, eastern Panama, and southern Brazil. The wide distribution of the gene for OCA2 in Amerindian populations, and its relatively high frequency in several of these populations, are enigmatic because of the detrimental nature of OCA2 in the presence of certain environmental conditions. The relative Darwinian fitness of individuals with this inborn error of metabolism would have been reduced in early nomadic hunting-gathering populations because of their poor visual acuity and sensitivity to the sun. Nevertheless, specific situations allowed OCA2 to increase in frequency in certain Amerindian populations at various different times in history. The present objectives are to review the literature on albinism (OCA2) in Amerindians, and propose hypotheses for the variable frequencies of the OCA2 gene in Amerindian populations, which include chance processes (founder effect, bottleneck effect, and genetic drift) in small populations, natural selection, cultural selection, and the interaction of situations that led to the increase of the frequency of the albino gene in some generations. Special emphasis is placed on those Amerindian populations with a relatively high frequency of the OCA2 gene that have been best-studied, namely, the Cuna population of eastern Panama and the Hopi population in the southwestern US. Hypothetical scripts are presented for the present relatively high frequencies of the OCA2 gene in these populations. A hypothetical script is also presented, showing how a mutant gene could have reached a relatively high frequency in a small endogamous early Mayan population and then been spread by migrating groups to other geographical regions, following the rapid increase in size of that population. Comprehensive molecular studies of OCA2 genes in Amerindian populations could yield information on the possible origin of the albino gene present in many of these populations, in addition to the gene flow that occurred among some of them in past generations. The results of these studies could lead to more informed hypotheses concerning the wide distribution of OCA2 in Amerindian populations.

The Darwinian concept of stress: benefits of allostasis and costs of allostatic load and the trade-offs in health and disease

Why do we get the stress-related diseases we do? Why do some people have flare ups of autoimmune disease, whereas others suffer from melancholic depression during a stressful period in their life? In the present review possible explanations will be given by using different levels of analysis. First, we explain in evolutionary terms why different organisms adopt different behavioral strategies to cope with stress. It has become clear that natural selection maintains a balance of different traits preserving genes for high aggression (Hawks) and low aggression (Doves) within a population. The existence of these personality types (Hawks-Doves) is widespread in the animal kingdom, not only between males and females but also within the same gender across species. Second, proximate (causal) explanations are given for the different stress responses and how they work. Hawks and Doves differ in underlying physiology and these differences are associated with their respective behavioral strategies; for example, bold Hawks preferentially adopt the fight-flight response when establishing a new territory or defending an existing territory, while cautious Doves show the freeze-hide response to adapt to threats in their environment. Thus, adaptive processes that actively maintain stability through change (allostasis) depend on the personality type and the associated stress responses. Third, we describe how the expression of the various stress responses can result in specific benefits to the organism. Fourth, we discuss how the benefits of allostasis and the costs of adaptation (allostatic load) lead to different trade-offs in health and disease, thereby reinforcing a Darwinian concept of stress. Collectively, this provides some explanation of why individuals may differ in their vulnerability to different stress-related diseases and how this relates to the range of personality types, especially aggressive Hawks and non-aggressive Doves in a population. A conceptual framework is presented showing that Hawks, due to inefficient management of mediators of allostasis, are more likely to be violent, to develop impulse control disorders, hypertension, cardiac arrhythmias, sudden death, atypical depression, chronic fatigue states and inflammation. In contrast, Doves, due to the greater release of mediators of allostasis (surplus), are more susceptible to anxiety disorders, metabolic syndromes, melancholic depression, psychotic states and infection.

Kin-structured migration: Causes and consequences

Migration among local populations classically has been seen as the principal process retarding genetic microdifferentiation. However, as Sewall Wright pointed out long ago, migration may also act as a random differentiating force. In fact, when migrants comprise a biological kin group, migration may be considered a component of genetic drift. The causes of kin-structured migration (KSM) lie in the common, if not universal, tendency for kin to associate and cooperate. However, similar to genetic drift, KSM has its greatest effect in smaller populations and is most apparent in low-density fission-fusion societies such as the Yanomamo of South America and the Semai of Malaysia, and less salient in higher density, low-mobility populations such as those of the New Guinea Highlands. The evolutionary consequences of KSM begin with increased genetic variation among populations. Such intergroup variation provides a basis for group selection. The origin of larger-scale geographic differentiation can arise from kin-structured migrant groups colonizing new regions. Waves of colonizing kin-structured founder groups may produce gene frequency clines, mimicking demic diffusion and natural selection. Finally, because kin structuring reduces the effective size of a population, it may be speculated that the extremely small effective size inferred for ancestral populations of Homo sapiens may be an artifact of kin-structured demographically larger populations.

Nuclear and mitochondrial genetic variation in the Yanomamö: a test case for ancient DNA studies of prehistoric populations

Ancient DNA provides a potentially revolutionary way to study biological relationships in prehistoric populations, but genetic patterns are complex and require careful interpretation based on robust, well-tested models. In this study, nuclear and mitochondrial markers were compared in the Yanomamö, to assess how well each data set could differentiate among closely related groups. The villages selected for the study share a recent fission history and are closely related to each other, as would likely be the case among prehistoric peoples living in the same valley or region. The Yanomamö generally practice village-level endogamy, but some migration and gene flow are known to occur between villages. Nuclear and mitochondrial DNA data were compared using F-statistics and genetic distance analyses. The nuclear data performed as expected, males and females from the same village were similar, and the villages were genetically distinct, with the magnitude of genetic differences correlated with historical relationship. However, mtDNA analyses did not yield the expected results. The genetic distances between villages did not correlate with historical relationship, and the sexes were significantly different from each other in two villages. Both the Lane and Sublett and the Spence methods, used to test for archaeological residence patterns, were consistent with endogamy. Hence, ancient DNA can, in principle, provide us with a unique opportunity to study genetic structure and gene flow in archaeological populations. However, interpretations, particularly those based on single loci such as mitochondrial DNA, should be cautious because sex-specific migration and sampling issues may have dramatic effects.

International Genetic Epidemiology Society: commentary on Darkness in El Dorado by Patrick Tierney

The International Genetic Epidemiology Society (IGES) has examined the charges against James V. Neel and his colleagues contained in the recently published book by Patrick Tierney entitled Darkness in El Dorado: How Scientists and Journalists Devastated the Amazon (W.W. Norton, 2000). The book implicates Neel in causing or promoting an epidemic of measles among the Yanomamö Indians of Venezuela in 1968 leading to "hundreds if not thousands" of deaths by using a "dinosaur" vaccine (Edmonston B) as a deliberate "experiment" to test his "eugenic" theories. Tierney also attempts to link this research, funded by the Atomic Energy Commission (AEC), with a broader tapestry of human radiation experiments. To investigate these serious charges, the IGES undertook a thorough examination of most source documents referenced in Tierney's book, Neel's field logs, notes, first-hand reports, contemporary writings, film sound tracks, etc., and conducted interviews with many relevant persons. The IGES finds that these allegations are false. Neel was not a eugenicist and was in fact highly critical of both the scientific basis of eugenics and its coercive social policies. In this regard, Tierney has grossly misrepresented Neel's views on a wide range of social implications of modern civilization for the long-term health of the gene pool. Far from causing an epidemic of measles, Neel did his utmost to protect the Yanomamö from the ravages of the impending epidemic by a vaccination program using a vaccine that was widely used at the time and administered in an appropriate manner. There was nothing experimental about the vaccination program, which in fact severely hindered the primary scientific objectives of the expedition. Although the research was funded in large part by the AEC, there was no element of radiation research and the work had no connection with the ethical abuses that have been reported from AEC-sponsored radiation research, such as studies of heavy isotopes. Neel's seminal contributions to a broad range of topics in human genetics have been extensively chronicled elsewhere. His research on the Yanomamö in particular has provided unique insights into the evolutionary biology of our species, the role of sociocultural practices, such as kinship relationships and selective pressures in shaping the genetic diversity of primitive population isolates, as well as the general picture of health in such populations. The IGES decries the damage done to the reputation of one of its founders and its first President and the misperception this book may have caused about the conduct of research in genetic epidemiology. Ethical issues about scientific research in primitive populations deserve serious and wide discussion, but the IGES condemns the gross misrepresentation of the facts and demonization of the principal characters in this book.

The newly characterized colicin Y provides evidence of positive selection in pore-former colicin diversification

Two evolutionary mechanisms have been proposed in the process of protein diversification of the large family of antimicrobial toxins of Escherichia coli, known as the colicins. Data from previous studies suggest that the relatively rare nuclease colicins appear to diversify primarily through the action of positive selection, whilst the more abundant pore-former colicins appear to diversify through the action of recombination. The complete DNA sequence of the newly characterized colicin plasmid, pCol-Let, isolated from a Yanomama Indian of South America, is presented here. This plasmid encodes a newly identified pore-former colicin, colicin Y. DNA and protein sequence comparisons of the colicin Y gene cluster and the encoded proteins with those of published pore-former colicins provide the first evidence that positive selection may also act to increase pore-former colicin diversity.

Natural experimental models: the global search for biomedical paradigms among traditional, modernizing, and modern populations

During the past four decades, biomedical scientists have slowly begun to recognize the unique opportunities for studying biomedical processes, disease etiology, and mechanisms of pathogenesis in populations with unusual genetic structures, physiological characteristics, focal endemic disease, or special circumstances. Such populations greatly extend our research capabilities and provide a natural laboratory for studying relationships among biobehavioral, genetic, and ecological processes that are involved in the development of disease. The models presented illustrate three different types of natural experiments: those occurring in traditionally living, modernizing, and modern populations. The examples are drawn from current research that involves population mechanisms of adaptation among East African Turkana pastoralists; a search for etiology and mechanisms of pathogenesis of an emerging disease among the Yakut people of Siberia; and psychosocial stress, hypertension, and cardiovascular disease in women working outside the home in New York City and among subpopulations in Hawaii. The models in general, and the examples in specific, represent natural laboratories in which relatively small intrapopulation differences and large interpopulation differences can be used to evaluate health and disease outcomes.

Social transmission of reproductive behavior increases frequency of inherited disorders in a young-expanding population

The observation of high frequencies of certain inherited disorders in the population of Saguenay-Lac Saint Jean can be explained in terms of the variance and the correlation of effective family size (EFS) from one generation to the next. We have shown this effect by using the branching process approach with real demographic data. When variance of EFS is included in the model, despite its profound effect on mutant allele frequency, any mutant introduced in the population never reaches the known carrier frequencies (between 0.035 and 0.05). It is only when the EFS correlation between generations is introduced into the model that we can explain the rise of the mutant alleles. This correlation is described by a c parameter that reflects the dependency of children's EFS on their parents' EFS. The c parameter can be considered to reflect social transmission of demographic behavior. We show that such social transmission dramatically reduces the effective population size. This could explain particular distributions in allele frequencies and unusually high frequency of certain inherited disorders in some human populations.

Haplotypes of angiotensinogen in essential hypertension

The M235T polymorphism of the angiotensinogen gene (AGT) has been associated with essential and pregnancy-induced hypertension. Generation of haplotypes can help to resolve whether the T235 allele itself predisposes to the development of hypertension or acts as a marker of an unknown causal molecular variant. We identified 10 diallelic polymorphisms at the AGT locus and genotyped both a series of 477 probands of hypertensive families and 364 controls, all French Caucasians, as well as a series of 92 hypertensives and 122 controls from Japan. Despite a large ethnic difference in gene frequency, a significant association of T235 with hypertension was observed both in Cancasians (.46 vs. .38, P = .004) and in Japanese (.91 vs. .76, P = .002). In both groups, the G-->A substitution located at position -6 upstream of the initial transcription site occurred at the same frequency and in complete linkage disequilibrium with the T235 allele. No other polymorphism was found to be consistently associated with hypertension. Five informative haplotypes subdividing the T235 allele were generated. Whereas two of them were associated with hypertension in Caucasians, none of these two haplotypes (H3 and H4) reached statistical significance in Japanese. The analysis of the AGT-GT repeat revealed marked linkage disequilibriums between each of the diallelic polymorphisms and some (GT)n alleles, with similar patterns in the two populations. The strong disequilibrium between M235 and (GT)16 explained the increased frequency of that particular allele in French controls compared with hypertensives (.42 vs. .36, P < .01). The haplotype combining the M235T and G-6A polymorphisms appears as the ancestral allele of the human AGT gene and as the one associated with hypertension.

Genetic variation of the mitochondrial DNA genome in American Indians is at mutation-drift equilibrium

Several surveys have found evidence for founder effects in Amerindian mitochondrial DNA because of the existence of rare Asian morphs in high frequencies in some Amerindian populations and the occurrence of several new morphs not seen elsewhere in the world. These reports, however, do not address whether or not the present genetic variation in the mtDNA genome in Amerindians has reached the steady-state distribution predicted by the mutation-drift theory of population genetics. The present work suggests that in three Amerindian populations (Pima, Maya, and Ticuna) a steady state has apparently been reached, and hence the initial founder effect has probably dissipated during the evolution of Amerindians in the New World. This result is consistent with the genetic variation in nuclear genes in similar populations, shown through surveys of protein variation in earlier work and, more recently, in studies of restriction fragment length polymorphisms.

Health and demography of native Amazonians: historical perspective and current status

Native Amazonians have been the victims of two massive historical assaults, one at the time of the Conquest and the other during the Twentieth century. Due to epidemic disease and environmental destruction, many tribes have gone from contact to displacement, decimation, and extinction in a single generation. Deculturation and the construction of large development projects have had catastrophic effects on native populations. In many ways, native Amazonians have experienced a reverse of the "Epidemiologic Transition". Paradoxically, one of the effects of cultural disruption for some native Amazonians has been the loss of cultural controls on fertility with the result that high fertility has become a major health problem. Combined with rapid growth of non-indigenous Amazonian populations, deforestation, and urbanization, native Amazonians face grave obstacles to long-term survival.

A nonracial craniofacial perspective on human variation: A(ustralia) to Z(uni)

Dental and craniofacial measurements were collected for 57 samples from Asia, the Pacific, the aboriginal western hemisphere, and Europe. The craniofacial dimensions include many that are not obviously under the control of specific selective forces. Similar configurations for these in different samples should yield indications of recency of common ancestry according to the logic expressed by Darwin and evident in the relationships indicated by nuclear DNA comparisons. Dental dimensions, however, vary according to the length of time that different intensities in selective forces have been in operation. The craniofacial measurements were transformed into C scores and used to generate Euclidean distance dendrograms. When all the material was used to generate a single dendrogram, the European and Amerindian samples sorted into two regionally identifiable clusters, and the Asian and Pacific material sorted into the three clusters identified in separate previous studies: a Mainland Asian cluster, a Jomon-Pacific cluster and an Australo-Melanesian cluster. Since these clusters are based on variation in traits that are basically nonadaptive in nature, no hierarchical ranking is possible. The clusters simply reflect degree of relationship. This technique holds forth the promise of producing a nonracial assessment of the relationships of all the peoples of the world, past and present.