Distinguishing heat from light in debate over controversial fossils

Fossil organisms offer our only direct insight into how the distinctive body plans of extant organisms were assembled. However, realizing the potential evolutionary significance of fossils can be hampered by controversy over their interpretation. Here, as a guide to evaluating palaeontological debates, we outline the process and pitfalls of fossil interpretation. The physical remains of controversial fossils should be reconstructed before interpreting homologies, and choice of interpretative model should be explicit and justified. Extinct taxa lack characters diagnostic of extant clades because the characters had not yet evolved, because of secondary loss, or because they have rotted away. The latter, if not taken into account, will lead to the spurious assignment of fossils to basally branching clades. Conflicting interpretations of fossils can often be resolved by considering all the steps in the process of anatomical analysis and phylogenetic placement, although we must accept that some fossil organisms are simply too incompletely preserved for their evolutionary significance to be realized.     

干细胞研究伦理

干细胞具有＂分化＂和＂脱分化＂的特点和潜能,干细胞研究有着良好的医学前景,许多人类严重疾病的治疗有了新的希望。伴随着干细胞研究的开展和深入,出现了诸多伦理问题的争论。拟就干细胞研究的希望和现实、伦理争论的主要观点及干细胞研究伦理准则的构建,作一简要介绍,并就加强干细胞管理提出建议。     

Finding fault with health risk assessment: A typology for risk assessment criticism

Although systematic, quantitative assessment of environmental health risks is a staple of regulatory decision-making, complaints regarding its perceived failures and shortcomings are an intrinsic feature of the policy landscape. In this article, we (a) catalog the classic criticisms of conventional health risk assessment, (b) create a typology that orders the critiques according to their focus on either input errors or output biases, and (c) identify selected allegations that fall within each category. We also note that the risk assessment–risk management paradigm has evolved over the past several decades, partially in accordance with the general direction and spirit of these classic critiques. The debate continues today along familiar lines invoking the traditional critiques and rebuttals outlined here.     

Statistical and algorithmic methods for fluctuation analysis with SALVADOR as an implementation

This paper aims at removing certain long-standing impediments to more effective and widespread use of fluctuation analysis. The paper presents a method of constructing confidence intervals for mutation rates using data from fluctuation experiments. The method was inspired by a rediscovery of a little-known, not fully developed method of Lea and Coulson; substantial modifications have been made both to enhance computational efficiency and to widen the scope of the original method's applicability. A computer package named SALVADOR is presented that can be used for Monte Carlo simulation, for point and interval estimation of mutation rates, and for exploration of various hypotheses spawned by the directed mutation controversy. In addition to the maximum likelihood method, methods of considerable historical interest are also examined and included in SALVADOR to help the reader compare and assess some of the most popular methods for estimating mutation rates.     

The Politics of Anti-Creationism: The Committees of Correspondence

When the creationism issue rose to the surface in the late 1970s, an organized opposition to the creationist campaign came from an unexpected source. Local groups of rank and file evolution defenders, led by a retired biology teacher, organized a grassroots network of anti-creationism called the Committees of Correspondence. They basically approached the creationism issue as a political rather than a scientific problem and fought the battle on local fronts, where creationists were heavily engaged in legal campaigns to include their ideas in the public schools. Grassroots anti-creationism was, however, eventually replaced by a centralized national operation with an educational emphasis. In this paper, I will document the development of this neglected part of the creation-evolution controversy and discuss related issues, namely the politics of science that became clearly visible in the course of evolutionists' disputes over anti-creation strategies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Marvelling at the Marvel: The Supposed Conversion of A.D. Darbishire to Mendelism

The so-called “biometric-Mendelian controversy” has received much attention from science studies scholars. This paper focuses on one scientist involved in this debate, Arthur Dukinfield Darbishire, who performed a series of hybridization experiments with mice beginning in 1901. Previous historical work on Darbishire’s experiments and his later attempt to reconcile Mendelian and biometric views describe Darbishire as eventually being “converted”' to Mendelism. I provide a new analysis of this episode in the context of Darbishire’s experimental results, his underlying epistemology, and his influence on the broader debate surrounding the rediscovery and acceptance of Mendelism. Iinvestigate various historiographical issues raised by this episode in order to reflect on the idea of “conversion” to a scientific theory. Darbishire was an influential figure who resisted strong forces compelling him to convert prematurely due to his requirements that the new theory account for particularly important anomalous facts and answer the most pressing questions in the field. This revised version was published online in July 2006 with corrections to the Cover Date.     

R. A. Fisher, Lancelot Hogben, and the Origin(s) of Genotype–Environment Interaction

This essay examines the origin(s) of genotype–environment interaction, or G × E. “Origin(s)” and not “the origin” because the thesis is that there were actually two distinct concepts of G × E at this beginning: a biometric concept, or G × E_B, and a developmental concept, or G × E_D. R. A. Fisher, one of the founders of population genetics and the creator of the statistical analysis of variance, introduced the biometric concept as he attempted to resolve one of the main problems in the biometric tradition of biology – partitioning the relative contributions of nature and nurture responsible for variation in a population. Lancelot Hogben, an experimental embryologist and also a statistician, introduced the developmental concept as he attempted to resolve one of the main problems in the developmental tradition of biology – determining the role that developmental relationships between genotype and environment played in the generation of variation. To argue for this thesis, I outline Fisher and Hogben’s separate routes to their respective concepts of G × E; then these separate interpretations of G × E are drawn on to explicate a debate between Fisher and Hogben over the importance of G × E, the first installment of a persistent controversy. Finally, Fisher’s G × E_B and Hogben’s G × E_D are traced beyond their own work into mid-20th century population and developmental genetics, and then into the infamous IQ Controversy of the 1970s.     

Morphometric analysis of disjunctPapaver radicatum (Papaveraceae) populations in southern Norway

Morphometric relationships between populations ofPapaver radicatum within the southern Norwegian mountains were investigated using canonical variates analysis andWard's clustering on capsule and leaf character sets. The survey describes patterns of variation among 13 wild-scored populations from five geographically disjunct localities, usually assigned to five races or subspecies. Our results from wild-collected material largely support earlier findings based on univariate statistics on cultivated material. In general, populations from within a disjunct locality (=subspecies) are most similar to other populations from the same locality. However, the subspecies vary in the degree to which they are differentiated in capsule morphology. The subsp.groevudalense populations are morphologically close to the main group of subsp.ovatilobum populations. Subspp.intermedium andoeksendalense are clearly distinct from one another and from the other subspecies, whereas the single subsp.gjaerevolli population is more similar to theovatilobum/groevudalense complex. Variation in leaf characters showed only partial congruence with variation in capsule characters. The pattern of morphological relationships among the subspecies is thus more complex than previously thought. The subspecies may have become differentiated during a period of isolation, but such results alone cannot indicate the duration of such a period.     

Data Do Not Speak for Themselves: The Role of Data in Scientific Controversies

This article presents a learning cycle with the aim of helping students understand the evidentiary basis of scientific claims. Students consider data and interpretations as used to support contradictory views in the debate surrounding the causal relationship between human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS). Students apply their understandings of the role of data to explorations of other scientific controversies.