Rethinking in African Studies

Book reviewed in this article:
Living under Contract: Contract Farming and Agrarian Transformation in Sub-Saharan Africa . Peter D. Little and Michael J. Watts, eds.
African Pastoralist Systems: An Integrated Approach . Elliot Fratkin, Kathleen A. Galvin, and Eric Abella Roth, eds.
Houses in the Rainforest: Ethnicity and Inequality among Farmers and Foragers in Central Africa . Roy Richard Grinker.     

Evolutionary History of the Vertebrate Period Genes

Circadian clock genes are remarkably conserved between eucoelomates. Although Drosophila has one copy of each major component, vertebrates have two or (in the case of the Period genes) three paralogs (Per1-3). We investigated the possibility that the vertebrate Per genes arose through two genome duplications during the emergence of vertebrates. Phylogenetic trees have placed zebrafish and mammalian Per1 and 2 together in a separate branch from Per3. The positions of four coding region splice sites were conserved between Drosophila per and the human paralogs, the fifth one being unique to Drosophila. The human PER genes shared the positions of all coding region splice sites, except the first two in PER1 and PER2 (which PER3 lacks). The phases of all splice sites were conserved between all four genes with two exceptions. Analysis of all genes within 10 Mb of the human PER1-3 genes, which are located 7.8—8.8 Mb from the telomeres on chromosomes 17, 2, and 1, identified several orthologous neighbors shared by at least two PER genes. Two gene families, HES (hairy and Enhancer of Split) and KIF1 (kinesin-like protein 1), were represented in all three of these paralogons. Although no functional fourth human PER paralog exists, five representatives from the same gene families were found close to the telomer of chromosome 3. We conclude that the ancestral chordate Per gene underwent two duplication events, giving rise to Per1—3 and a lost fourth paralog. [Reviewing Editor: Dr. John Onkeshott]     

Evolutionary Morphology, Innovation, and the Synthesis of Evolutionary and Developmental Biology

One foundational question in contemporarybiology is how to `rejoin evolution anddevelopment. The emerging research program(evolutionary developmental biology or`evo-devo) requires a meshing of disciplines,concepts, and explanations that have beendeveloped largely in independence over the pastcentury. In the attempt to comprehend thepresent separation between evolution anddevelopment much attention has been paid to thesplit between genetics and embryology in theearly part of the 20th century with itscodification in the exclusion of embryologyfrom the Modern Synthesis. This encourages acharacterization of evolutionary developmentalbiology as the marriage of evolutionary theoryand embryology via developmental genetics. Butthere remains a largely untold story about thesignificance of morphology and comparativeanatomy (also minimized in the ModernSynthesis). Functional and evolutionarymorphology are critical for understanding thedevelopment of a concept central toevolutionary developmental biology,evolutionary innovation. Highlighting thediscipline of morphology and the concepts ofinnovation and novelty provides an alternativeway of conceptualizing the `evo and the `devoto be synthesized.     

The Main Directions of Studies in Evolutionary Immunology

The main directions in evolutionary immunology include: (1) study of phylogenetic relationships between nonspecific (innate) and specific (acquired, or adaptive) immunity; (2) study of the phenomena of graft rejection in a phylogenetic series; (3) study of occurrence and historical development of T- and B-systems of immunity; (4) study of phylogeny of different cell types of the immune system; and (5) study of historical development of the ability to specifically recognize foreign antigenic material. Because many problems of evolutionary immunology remain unsolved, studies in this field will be continued.     

Woodger, Positivism, and the Evolutionary Synthesis

In Unifying Biology, Smocovitis offers a series of claimsregarding the relationship between key actors in the synthesisperiod of evolutionary studies and positivism, especially claimsentailing Joseph Henry Woodger and the Unity of Science Movement.This commentary examines Woodger's possible relevance to key synthesis actors and challenges Smocovitis' arguments for theexplanatory relevance of logical positivism, and positivism moregenerally, to synthesis history. Under scrutiny, these arguments areshort on evidence and subject to substantial conceptual confusion.Though plausible, Smocovitis' minimal interpretation – that somegeneralised form of Comtean positivism had a role in synthesishistory – requires more of an evidential basis and must engageexisting scholarship on epistemic reforms in the biological sciencesprior to the synthesis period. Smocovitis is right to investigateepistemology in the synthesis period of evolutionary studies and tolook for links to wider changes in science and philosophy. However,in its present form, Unifying Biology fails to support herbasic interpretation.     

Mendelian-Mutationism: The Forgotten Evolutionary Synthesis

According to a classical narrative, early geneticists, failing to see how Mendelism provides the missing pieces of Darwin’s theory, rejected gradual changes and advocated an implausible yet briefly popular view of evolution-by-mutation; after decades of delay (in which synthesis was prevented by personal conflicts, disciplinary rivalries, and anti-Darwinian animus), Darwinism emerged on a new Mendelian basis. Based on the works of four influential early geneticists – Bateson, de Vries, Morgan and Punnett –, and drawing on recent scholarship, we offer an alternative that turns the classical view on its head. For early geneticists, embracing discrete inheritance and the mutation theory (for the origin of hereditary variation) did not entail rejection of selection, but rejection of Darwin’s non-Mendelian views of heredity and variation, his doctrine of natura non facit saltum, and his conception of “natural selection” as a creative force that shapes features out of masses of infinitesimal differences. We find no evidence of a delay in synthesizing mutation, rules of discrete inheritance, and selection in a Mendelian-Mutationist Synthesis. Instead, before 1918, early geneticists had conceptualized allelic selection, the Hardy–Weinberg equilibrium, the evolution of a quantitative trait under selection, the probability of fixation of a new mutation, and other key innovations. Contemporary evolutionary thinking seems closer to their more ecumenical view than to the restrictive mid-twentieth-century consensus known as the Modern Synthesis.     

Evolutionary Studies Illuminate the Structural-Functional Model of Plant Phytochromes

A synthesis of insights from functional and evolutionary studies reveals how the phytochrome photoreceptor system has evolved to impart both stability and flexibility. Phytochromes in seed plants diverged into three major forms, phyA, phyB, and phyC, very early in the history of seed plants. Two additional forms, phyE and phyD, are restricted to flowering plants and Brassicaceae, respectively. While phyC, D, and E are absent from at least some taxa, phyA and phyB are present in all sampled seed plants and are the principal mediators of red/far-red–induced responses. Conversely, phyC-E apparently function in concert with phyB and, where present, expand the repertoire of phyB activities. Despite major advances, aspects of the structural-functional models for these photoreceptors remain elusive. Comparative sequence analyses expand the array of locus-specific mutant alleles for analysis by revealing historic mutations that occurred during gene lineage splitting and divergence. With insights from crystallographic data, a subset of these mutants can be chosen for functional studies to test their importance and determine the molecular mechanism by which they might impact light perception and signaling. In the case of gene families, where redundancy hinders isolation of some proportion of the relevant mutants, the approach may be particularly useful.     

Evolutionary Novelty and the Evo-Devo Synthesis: Field Notes

Accounting for the evolutionary origins of morphological novelty is one of the core challenges of contemporary evolutionary biology. A successful explanatory framework requires the integration of different biological disciplines, but the relationships between developmental biology and standard evolutionary biology remain contested. There is also disagreement about how to define the concept of evolutionary novelty. These issues were the subjects of a workshop held in November 2009 at the University of Alberta. We report on the discussion and results of this workshop, addressing questions about (i) how to define evolutionary novelty and understand its significance, (ii) how to interpret evolutionary developmental biology as a synthesis and its relation to neo-Darwinian evolutionary theory, and (iii) how to integrate disparate biological approaches in general.     

An Evolutionary Perspective on Linoleic Acid Synthesis in Animals

The diet of organisms generally provides a sufficient supply of energy and building materials for healthy growth and development, but should also contain essential nutrients. Species differ in their exogenous requirements, but it is not clear why some species are able to synthesize essential nutrients, while others are not. The unsaturated fatty acid, linoleic acid (LA; 18:2n-6) plays an important role in functions such as cell physiology, immunity, and reproduction, and is an essential nutrient in diverse organisms. LA is readily synthesized in bacteria, protozoa and plants, but it was long thought that all animals lacked the ability to synthesize LA de novo and thus required a dietary source of this fatty acid. Over the years, however, an increasing number of studies have shown active LA synthesis in animals, including insects, nematodes and pulmonates. Despite continued interest in LA metabolism, it has remained unclear why some organisms can synthesize LA while others cannot. Here, we review the mechanisms by which LA is synthesized and which biological functions LA supports in different organisms to answer the question why LA synthesis was lost and repeatedly gained during the evolution of distinct invertebrate groups. We propose several hypotheses and compile data from the available literature to identify which factors promote LA synthesis within a phylogenetic framework. We have not found a clear link between our proposed hypotheses and LA synthesis; therefore we suggest that LA synthesis may be facilitated through bifunctionality of desaturase enzymes or evolved through a combination of different selective pressures.     

The Definition and Measurement of Individual Condition in Evolutionary Studies

Over the past four decades, as the use of the term condition has become more frequent, the meaning of the term has become increasingly vague. This is especially true in evolutionary theory where condition is now equated with reproductive value, genetic quality, or defined as the ‘total pool of resources available for reproduction.’ Condition with the latter meaning is essentially impossible to measure empirically because it is associated with multiple attributes, such as nutritional state, health, experience, foraging success, ability to cope with environmental pressures, and social status, that collectively affect individual fitness. The addition of qualifying terms that often precede condition (e.g., phenotypic, energetic, and nutritional) and the usage of terms that describe an individual's state (e.g., physiological state, energetic state, and nutritional state) add confusion to the issue. It is therefore important to evaluate the meaning of condition, the limits of its usefulness, and how it can be best measured. We suggest using a more narrow definition of condition, amenable to empirical study, would benefit evolutionary and behavioral studies.     

Rethinking Global and Area Studies: Insights from Caribbeanist Anthropology

Recently, there has been an upsurge in the critical attention directed toward the area studies research paradigms that were institutionalized after World War II. This upsurge comes at a time when anthropologists are also developing increasingly sophisticated accounts of the intersections of global and local processes. Yet there has been less engaged consideration of the agendas propelling global studies over area studies curricula. In this essay, we argue that an analysis of the Caribbean and Caribbeanist anthropology allows us to trace the global in the local, thus illustrating the benefits of local area analyses for understanding global dynamics. We draw on theoretical assertions regarding global–local interactions in order to assess the relation of anthropology to Caribbean studies and to explore the implications of analytical trajectories and theoretical developments within Caribbeanist anthropology for social and cultural processes on a global level. [Keywords: area studies, anthropological theory, the Caribbean, transnationalism]     

Rethinking Anthropological Studies of the Body: Manas and Bōdham in Kerala

Anthropological research that focuses on the body has been prolific in the last two decades. This trend has provided an important reorientation away from a tendency to focus on mental representations of experience and has allowed for a more holistic understanding of the human condition. However, this article argues that much research on the body has created a false dichotomy: Westerners are seen as living in a world of mentalistic bias and mind–body dualism while all others are understood as more grounded in their bodies. Ethnographic research conducted among people suffering psychopathology and possession in Kerala, India, challenges these assumptions about the embodied Other by showing that these patients experience a continuum of states of being that includes the body, mind, consciousness, and self/soul. This approach demonstrates how an examination of a local culturally and historically formed phenomenological orientation can provide a useful alternative to the tendency to discover embodied peoples. [Keywords: body, embodiment, India, Kerala]     

Cactophilic Drosophila in South America: A Model for Evolutionary Studies

The Drosophila buzzatii cluster is composed of seven cactophilic species and their known geographical distribution encompasses the open vegetation diagonal, which includes the morphoclimatic Domains of the Caatinga, Chaco and Cerrado, which are situated between the Amazon and the Atlantic forests. Besides these areas, these cactophilic species are also found in a narrow strip along the Atlantic coast from northeastern Brazil to the southern tip of the country. The hypothesis of vicariant events, defining the core areas of each species, is proposed to explain the historical diversification for the cluster. The intraspecific analysis for the cluster shows a population structure with gene flow restricted by distance, range expansion with secondary contact resulting in introgression and simpatry, especially in the limits of the species distribution, polytypic populations and assortative mating in inter population experiments. There is a variation related to these events that depends on the species and geographic origin of the population analyzed. These events are, hypothetically, described as the results of expansion and retraction of the population ranges, as a consequence of their association with cacti, which theoretically follow the expansion and retraction of dry areas during the paleoclimatic oscillations in South America, as that promoted by the glacial cycles of the Quaternary. The Drosophila buzzatii cluster is divided into two groups. The first one is composed of D. buzzatii, a species that has a broad geographic distribution and no significant differentiation between its populations. The second is the Drosophila serido sibling set, which encompasses the others species and is characterized by a significant potential for differentiation.     

慈姑属植物的生态及进化生物学研究进展

慈姑属(Sagittaria L.)隶属于泽泻科,是世界广布的水生植物,其生境多样、叶形和繁殖表型复杂,进化地位较特殊,是生态和进化生物学研究较典型的材料。笔者在查阅相关慈姑属研究的大量文献的基础上,对前人研究的物种、探讨的问题及研究结果进行了归纳与总结:慈姑属物种存在广布种和濒危种,且个别物种的濒危现状可能与其生境条件相关;慈姑属的个别种类成为稻田入侵杂草,其竞争能力因慈姑种类及水稻栽培品种的不同而各异;环境对慈姑属植物有很强的塑造作用,不同环境还会造成慈姑所在的水生植物群落结构发生变化;慈姑属植物具有较高的遗传多样性;在繁殖方面,慈姑属植物体现出不同繁殖方式和两性功能的权衡,以及在繁育系统上从雌雄同株到雌雄异株的进化途径。本文还提出了相关研究存在的不足、研究中应注意的科学问题,并对慈姑属植物未来的研究方向提供了新思路。     

Studies in the Synthesis and Biosynthesis of C-Nucleosides

Abstract

The naturally occurring C-nucleosides show marked antiturnour and antiviral properties. We have developed, over a period of years, a general synthetic route to C-nucleosides by way of acetylenic intermediates. Tri-O-benzyl-D-ribofuranose (1) reacts with acetylenic Grignard reagents to give mixtures of D-allo and D-altro diols. The latter, on ring closure by means of toluene-p-sulphonyl chloride in pyridine, gives derivatives, (2) or (3), of β-D-ribofuranosylethyne in ～50% yield from (1).