Human evolution

The origin, history, and singularity of our species has fascinated storytellers, philosophers and scientists throughout, and doubtless before, recorded history. Anthropology, the modern-era discipline that deals with these issues, is a notoriously contentious field, perhaps because the topic at hand – the nature of our own species – is one that is difficult or impossible to approach in an unbiased way. Recently, molecular genetics has increasingly contributed to this field. Here, I briefly discuss three areas where I believe molecular studies are likely to be of decisive importance in the future. These concern the questions of where and when our species originated, what the genetic background for characters that differ between us and apes is, and how the phenotypic traits that vary among human groups have evolved.     

Human evolution

The origin, history, and singularity of our species has fascinated storytellers, philosophers and scientists throughout, and doubtless before, recorded history. Anthropology, the modern-era discipline that deals with these issues, is a notoriously contentious field, perhaps because the topic at hand – the nature of our own species – is one that is difficult or impossible to approach in an unbiased way. Recently, molecular genetics has increasingly contributed to this field. Here, I briefly discuss three areas where I believe molecular studies are likely to be of decisive importance in the future. These concern the questions of where and when our species originated, what the genetic background for characters that differ between us and apes is, and how the phenotypic traits that vary among human groups have evolved.     

Human evolution

The origin, history, and singularity of our species has fascinated storytellers, philosophers and scientists throughout, and doubtless before, recorded history. Anthropology, the modern-era discipline that deals with these issues, is a notoriously contentious field, perhaps because the topic at hand – the nature of our own species – is one that is difficult or impossible to approach in an unbiased way. Recently, molecular genetics has increasingly contributed to this field. Here, I briefly discuss three areas where I believe molecular studies are likely to be of decisive importance in the future. These concern the questions of where and when our species originated, what the genetic background for characters that differ between us and apes is, and how the phenotypic traits that vary among human groups have evolved.     

Managing genetic testing: the relative powerlessness of actors in stable practices

Abstract

Genetics is a field in which ethical and social problems have been most pressing. Despite this, new tests often are introduced almost immediately after the isolation of a new gene. Considerations of whether a particular test should be introduced at all seem to have little effect on the development and introduction of new tests. This paper explores how this lack of social and ethical assessment can be understood. In order to do so, the sociohistorical context of clinical genetics and the way in which this practice came about will be analysed in this paper with respect to the Dutch service for clinical genetics. It will be argued that the fragmented way in which tasks and responsibility have become distributed within clinical genetics services has led to a situation in which actors seem to have no control over the introduction of genetic tests.     

Beyond Anthropology,Towards Actuality1

Anthropology in Australia is at a critical juncture. This paper discusses the way in which the discipline has been challenged at the institutional level, in part due to pressures arising from economic rationalisation within universities. Anthropology, however, must take some responsibility for its condition. Psychology has established itself as the primary ‘human’ discipline to provide qualifications appropriate for professional employment. At a more scholarly level, anthropology's traditional zones of concern have been taken over by others, including history and cultural studies. Can we, and should we, demystify anthropology and its practices? Can we reposition anthropology with a broader vision of the human experience, and what will happen if we cannot?     

The Counteracting Effects of Demography on Functional Genomic Variation: The Roma Paradigm

Demographic history plays a major role in shaping the distribution of genomic variation. Yet the interaction between different demographic forces and their effects in the genomes is not fully resolved in human populations. Here, we focus on the Roma population, the largest transnational ethnic minority in Europe. They have a South Asian origin and their demographic history is characterized by recent dispersals, multiple founder events, and extensive gene flow from non-Roma groups. Through the analyses of new high-coverage whole exome sequences and genome-wide array data for 89 Iberian Roma individuals together with forward simulations, we show that founder effects have reduced their genetic diversity and proportion of rare variants, gene flow has counteracted the increase in mutational load, runs of homozygosity show ancestry-specific patterns of accumulation of deleterious homozygotes, and selection signals primarily derive from preadmixture adaptation in the Roma population sources. The present study shows how two demographic forces, bottlenecks and admixture, act in opposite directions and have long-term balancing effects on the Roma genomes. Understanding how demography and gene flow shape the genome of an admixed population provides an opportunity to elucidate how genomic variation is modeled in human populations.     

Anthropology and the Third Information Revolution

This journal, Visual Anthropology, has now been in existence for a third of a century, and so it is an appropriate moment to look back at where we and our scholarship have come from, and what changes we have seen during our own lifetimes. This article first gives a rapid overview of the four major forms of information technology in human history. These were the age of oral transfer of messages, writing, printing, and lastly the age of mechanical reproduction, including the development of digital technologies. The rest of the article recalls the author’s own experience of the most recent period of computer and multi-media work. The first phase of this was the computer revolution from the 1960s to around the Millennium, the second is the spread of the high-speed internet with the accompanying tools on the web. The article ends by considering some of the implications for anthropology of the accumulated developments, in terms of on-line databases, digital repositories and personal publishing. Anthropology has been transformed during the author’s lifetime by the rapid growth of more powerful tools of communication, and it is likely that this will increase exponentially into the future. As anthropologists we need to see the big picture of how this has happened and what its implications are.     

Molecular evolution and modern human origins

While molecular evolutionists may be fascinated by the features and history of a particular gene or DNA segment, evolutionary anthropologists are often more interested in the activities and history of groups of people. We may want to know, for instance, when and where humans have migrated, how much exchange between groups has taken place, and how population sizes have changed. Population genetic theory provides the hope that through analyses of genetic data we will gain insight into the history of populations. Genetic data from extant human populations are now accruing at a remarkable rate. We might, therefore, expect to have answers in hand. There remains, however, a wide gap between the available theory and data; too often we fail to draw firm conclusions because our interpretation of analytic results requires that we make myriad assumptions about our data. In any one instance, these assumptions might include estimates of mutation rate, mutational mechanism, population sizes, the role that natural selection has played, and the rate of migration among groups. Often these assumptions are implicit, invisible to most. How, then, are we to make any progress? © 1998 Wiley-Liss, Inc.     

Contributions and promise of human behavioral genetics

Human behavioral genetics has contributed greatly to our understanding of human behavioral development. Twin, family, and adoption studies have shown that genetic effects are ubiquitous and that both genes and environments contribute to individual differences in behavior. The unique ability of behavioral genetic methods to separate genetic from environmental effects has also led to important discoveries about how the environment works in development and to the elucidation of the complex ways environments and genes interact across the life span. Although quantitative methods have been the mainstay of the field of human behavioral genetics since Galton's time, the Human Genome Project and advances in molecular genetics are providing new tools and promise as we enter the 21st century. Thus the future of human behavioral genetics lies in the cross-disciplinary exchanges and collaborations that will increasingly occur in the years to come among quantitative and molecular scientists who work with both animal and human systems. This research may someday culminate in an understanding of the biological basis of behavior that spans from how the brain develops and functions to a grasp of how genes influence thought at the molecular level.     

Fit for consumption: zebrafish as a model for tuberculosis

Despite efforts to generate new vaccines and antibiotics for tuberculosis, the disease remains a public health problem worldwide. The zebrafish Danio rerio has emerged as a useful model to investigate mycobacterial pathogenesis and treatment. Infection of zebrafish with Mycobacterium marinum, the closest relative of the Mycobacterium tuberculosis complex, recapitulates many aspects of human tuberculosis. The zebrafish model affords optical transparency, abundant genetic tools and in vivo imaging of the progression of infection. Here, we review how the zebrafish–M. marinum system has been deployed to make novel observations about the role of innate immunity, the tuberculous granuloma, and crucial host and bacterial genes. Finally, we assess how these findings relate to human disease and provide a framework for novel strategies to treat tuberculosis.KEY WORDS: Disease models, Genetics, Mycobacterium, Pathogenesis, Tuberculosis, Zebrafish     

Host and parasite life history interplay to yield divergent population genetic structures in two ectoparasites living on the same bat species

Host–parasite interactions are ubiquitous in nature. However, how parasite population genetic structure is shaped by the interaction between host and parasite life history remains understudied. Studies comparing multiple parasites infecting a single host can be used to investigate how different parasite life history traits interplay with host behaviour and life history. In this study, we used 10 newly developed microsatellite loci to investigate the genetic structure of a parasitic bat fly (Basilia nana). Its host, the Bechstein's bat (Myotis bechsteinii), has a social system and roosting behaviour that restrict opportunities for parasite transmission. We compared fly genetic structure to that of the host and another parasite, the wing‐mite, Spinturnix bechsteini. We found little spatial or temporal genetic structure in B. nana, suggesting a large, stable population with frequent genetic exchange between fly populations from different bat colonies. This contrasts sharply with the genetic structure of the wing‐mite, which is highly substructured between the same bat colonies as well as temporally unstable. Our results suggest that although host and parasite life history interact to yield similar transmission patterns in both parasite species, the level of gene flow and eventual spatiotemporal genetic stability is differentially affected. This can be explained by the differences in generation time and winter survival between the flies and wing‐mites. Our study thus exemplifies that the population genetic structure of parasites on a single host can vary strongly as a result of how their individual life history characteristics interact with host behaviour and life history traits.     

Resistance to oxidative stress shows low heritability and high common environmental variance in a wild bird

Oxidative stress was recently demonstrated to affect several fitness‐related traits and is now well recognized to shape animal life‐history evolution. However, very little is known about how much resistance to oxidative stress is determined by genetic and environmental effects and hence about its potential for evolution, especially in wild populations. In addition, our knowledge of phenotypic sexual dimorphism and cross‐sex genetic correlations in resistance to oxidative stress remains extremely limited despite important evolutionary implications. In free‐living great tits (Parus major), we quantified heritability, common environmental effect, sexual dimorphism and cross‐sex genetic correlation in offspring resistance to oxidative stress by performing a split‐nest cross‐fostering experiment where 155 broods were split, and all siblings (n = 791) translocated and raised in two other nests. Resistance to oxidative stress was measured as both oxidative damage to lipids and erythrocyte resistance to a controlled free‐radical attack. Both measurements of oxidative stress showed low additive genetic variances, high common environmental effects and phenotypic sexual dimorphism with males showing a higher resistance to oxidative stress. Cross‐sex genetic correlations were not different from unity, and we found no substantial heritability in resistance to oxidative stress at adult age measured on 39 individuals that recruited the subsequent year. Our study shows that individual ability to resist to oxidative stress is primarily influenced by the common environment and has a low heritability with a consequent low potential for evolution, at least at an early stage of life.     

Evolutionary implications of mitochondrial genetic variation: mitochondrial genetic effects on OXPHOS respiration and mitochondrial quantity change with age and sex in fruit flies

The ancient acquisition of the mitochondrion into the ancestor of modern‐day eukaryotes is thought to have been pivotal in facilitating the evolution of complex life. Mitochondria retain their own diminutive genome, with mitochondrial genes encoding core subunits involved in oxidative phosphorylation. Traditionally, it was assumed that there was little scope for genetic variation to accumulate and be maintained within the mitochondrial genome. However, in the past decade, mitochondrial genetic variation has been routinely tied to the expression of life‐history traits such as fertility, development and longevity. To examine whether these broad‐scale effects on life‐history trait expression might ultimately find their root in mitochondrially mediated effects on core bioenergetic function, we measured the effects of genetic variation across twelve different mitochondrial haplotypes on respiratory capacity and mitochondrial quantity in the fruit fly, Drosophila melanogaster. We used strains of flies that differed only in their mitochondrial haplotype, and tested each sex separately at two different adult ages. Mitochondrial haplotypes affected both respiratory capacity and mitochondrial quantity. However, these effects were highly context‐dependent, with the genetic effects contingent on both the sex and the age of the flies. These sex‐ and age‐specific genetic effects are likely to resonate across the entire organismal life‐history, providing insights into how mitochondrial genetic variation may contribute to sex‐specific trajectories of life‐history evolution.     

The social modes of men

Here we attempt to define a specifically human ecology within which male reproductive strategies are formulated. By treating the domestic and public spheres of social life as "ecological niches" that men have been forced to compete within or to avoid as best they can, we generate a typology of four "social modes" of human male behavior. We then attempt to explain the broad distribution of social modes within and between human groups based on the relative intensity of scramble and contest competition. This research was completed with the help of a Lowell M. Durham, Jr. Fellowship at the Tanner Humanities Center, University of Utah. Lars Rodseth (Ph.D., University of Michigan 1993) is Assistant Professor of Anthropology at the University of Utah. He has conducted fieldwork in Nepal and Micronesia and is the author of "Distributive Models of Culture: A Sapirian Alternative to Essentialism," American Anthropologist (1998) 100:55–69. Shannon A. Novak (Ph.D., University of Utah 1999) is Assistant Professor of Anthropology at Indiana State University. She has conducted fieldwork in Croatia and the United Kingdom and is the author of "Perimortem Processing of Human Remains among the Great Basin Fremont," International Journal of Osteoachaeology (2000) 10:65–75.     

遗传学视角下东亚人群的起源和演化

东亚是研究解剖学意义上现代人迁徙和演化的重要地带之一,该地区现代人群的起源及形成问题一直都是人类学领域广泛关注的焦点。遗传学研究为重建东亚人群历史提供了新的视角和见解。越来越多的遗传学证据表明,现代人约20万年前起源于非洲的晚期智人,并于10万年前走出非洲,大约在5~6万年前沿海岸线快速到达东亚南部,进而扩散到整个东亚地区。早期智人可能对走出非洲的现代人有一定程度的遗传贡献。早期定居、文化同化、人群迁徙以及基因交流等,对东亚人群的起源和演化起着至关重要的作用。前期的研究对东亚人群的源流历史进行了细致的分析,很大程度上解决了考古学、历史学等领域长期以来存在的分歧,然而这还需通过全基因组学和古DNA研究的进一步验证。本文从遗传学视角梳理和总结了东亚人群起源、迁徙和演化的历史,完善了对东亚人群演变的系统认识,并对未来东亚人群源流历史研究的发展方向做了展望。     

Population genomic variation reveals roles of history,adaptation and ploidy in switchgrass

Geographic patterns of genetic variation are shaped by multiple evolutionary processes, including genetic drift, migration and natural selection. Switchgrass (Panicum virgatum L.) has strong genetic and adaptive differentiation despite life history characteristics that promote high levels of gene flow and can homogenize intraspecific differences, such as wind‐pollination and self‐incompatibility. To better understand how historical and contemporary factors shape variation in switchgrass, we use genotyping‐by‐sequencing to characterize switchgrass from across its range at 98 042 SNPs. Population structuring reflects biogeographic and ploidy differences within and between switchgrass ecotypes and indicates that biogeographic history, ploidy incompatibilities and differential adaptation each have important roles in shaping ecotypic differentiation in switchgrass. At one extreme, we determine that two Panicum taxa are not separate species but are actually conspecific, ecologically divergent types of switchgrass adapted to the extreme conditions of coastal sand dune habitats. Conversely, we identify natural hybrids among lowland and upland ecotypes and visualize their genome‐wide patterns of admixture. Furthermore, we determine that genetic differentiation between primarily tetraploid and octoploid lineages is not caused solely by ploidy differences. Rather, genetic diversity in primarily octoploid lineages is consistent with a history of admixture. This suggests that polyploidy in switchgrass is promoted by admixture of diverged lineages, which may be important for maintaining genetic differentiation between switchgrass ecotypes where they are sympatric. These results provide new insights into the mechanisms shaping variation in widespread species and provide a foundation for dissecting the genetic basis of adaptation in switchgrass.     

The public health implications of maternal care trade-offs

The socioeconomic and ethnic characteristics of parents are some of the most important correlates of adverse health outcomes in childhood. However, the relationships between ethnic, economic, and behavioral factors and the health outcomes responsible for this pervasive finding have not been specified in child health epidemiology. The general objective of this paper is to propose a theoretical approach to the study of maternal behaviors and child health in diverse ethnic and socioeconomic environments. The specific aims are: (a) to describe a causal pathway between the utility that women obtain through work outside the home and through child care and disease hazard rates in childhood using an optimization model; (b) to specify the influence of ethnic and socioeconomic factors on model constraints; (c) to use the model as a tool to learn about how different combinations of maternal wage labor and child care time might influence child health outcomes in diverse social contexts; (d) to identify parameters that will require measurement in future research; (e) to discuss research strategies that will enable us to obtain these measurements; and (f) to discuss the implications of the model for biostatistical modeling and public health intervention. Optimization models are powerful heuristic tools for understanding how ethnic, environmental, family, and personal characteristics can place important constraints on both the quality and quantity of care that women can provide to their children. They provide a quantitative appreciation for the difficult trade-offs that most women face between working in order to purchase basic goods that children cannot do without (e.g., food, clothing, shelter, health insurance), and increasing offspring well-being through child care (e.g., training in social skills, affection, protection from environmental hazards, help with homework). The research was funded by a Faculty Scholars Award from the William T. Grant Foundation to A. Magdalena Hurtado. A. Magdalena Hurtado, Ph.D., is an associate professor in the Department of Anthropology, University of New Mexico. Her research interests include the origins of the sexual division of labor, epidemiology of indigenous peoples, disease susceptibility, the development and intergenerational transmission of antigens and immune defense, immune function and allergic sensitization, and trauma. She also works on public health interventions, biological capital and poverty, and land tenure and human rights in native communities of South America. Carol Lambourne, M.Sc., is a doctoral candidate in the Department of Anthropology, University of New Mexico. Her research interests are evolutionary models of child and adolescent development, life history theory, family composition and investment patterns, pubertal timing and psychosexual maturation, juvenile stress, and infanticide. Kim Hill, Ph.D., is a professor in the Department of Anthropology, University of New Mexico. His research interests are modern hunter-gatherers, including extensive fieldwork in lowland South America. Current topics of interest include human evolution, economic strategies, life history theory, the evolution of cooperation, and the emergence of social norms enforced by punishment. He is also involved in economic development, health and education projects with lowland South American native populations. Karen Kessler received her M.S. in Anthropology from the University of New Mexico in 1996. Her research interests are the application of mathematical modeling to the prevention of diabetes and other causes of morbidity and mortality in historical populations.     

Maternal and paternal contributions to egg size and egg number variation in the blackfin pearl killifish <Emphasis Type="Italic">Austrolebias nigripinnis</Emphasis>

Reproductive effort, egg number and egg size are traditionally considered to be ‘female’ life history traits. However, females often adjust the amount of resources allocated to reproduction depending on their mate, causing male environmental effects on life history traits. If females respond to male traits which are genetically variable, then male environmental effects contain indirect genetic effects. Estimates of how much of the total variation in life history traits originates from female effects versus male environmental effects, seems mostly lacking. We have investigated variation in rates of egg production and in egg size in the annual Argentinian blackfin pearl killifish Austrolebias nigripinnis, in a crossed design where males were exchanged repeatedly between females. Our analysis of phenotypic variance components of reproductive effort, egg size and egg number indicates that the amount of variation contributed by male environmental effects is equal (egg size, reproductive effort) or larger (egg number) than that between females. For egg size and number, we find that male environmental effects consist of a male random effect representing the average response of females to male phenotype, plus a female-male interaction term. This term can be understood as the deviation from the population mean of an individual female’s response. For reproductive effort, we find that the male environmental effect consists of an interaction term only. Random effects on egg size and number additionally vary in magnitude depending on the weekday where we collected eggs, probably due to cyclic variation in experimental conditions. Since we find that both male phenotype and environmental conditions affect egg size and number as determined by females, our results suggest that selection on these life history traits will be frequency-dependent.     

Little epistasis for anxiety-related measures in the DeFries strains of laboratory mice

Recent advances in methodologies for testing epistatic interactions, combined with several successes in demonstrating genetic interaction effects in animal and human genetics, have rekindled interest in the role of epistatic influences on complex traits. It has even been suggested that the unacknowledged presence of epistasis vitiates the genetic dissection of human and animal behavior. Here we report a genome-wide interaction analysis of 1636 F₂ mice to show that epistasis is of minimal importance in an animal model of anxiety. By using a sufficiently large sample of F₂ animals, we provide evidence that interaction effects between any two loci contribute less than 5% to the total phenotypic variance in multiple tests of anxiety. We conclude that interactions between loci do not necessarily vitiate the genetic analysis of behavior in at least one animal model of anxiety.     

Unraveling male and female histories from human genetic data

The increasing availability of large-scale genetic datasets has made it possible to ask detailed questions about the structure of human genetic diversity, and what that structure can teach us about human demographic history. Global, multi-locus analyses have suggested that human genetic diversity may fall into clusters that correspond approximately to continental origin. Detailed comparisons of mitochondrial DNA and the Y chromosome have revealed a history of sex-biased migration patterns that can vary widely across human populations. These patterns can be understood, however, when we incorporate our knowledge of local histories and cultural practices into our genetic analyses.