Two decades of suspect evidence for adaptive molecular evolution—negative selection confounding positive-selection signals

There has been a large literature in the last two decades affirming adaptive DNA sequence evolution between species. The main lines of evidence are from (i) the McDonald-Kreitman (MK) test, which compares divergence and polymorphism data, and (ii) the phylogenetic analysis by maximum likelihood (PAML) test, which analyzes multispecies divergence data. Here, we apply these two tests concurrently to genomic data of Drosophila and Arabidopsis. To our surprise, the >100 genes identified by the two tests do not overlap beyond random expectation. Because the non-concordance could be due to low powers leading to high false negatives, we merge every 20–30 genes into a ‘supergene’. At the supergene level, the power of detection is large but the calls still do not overlap. We rule out methodological reasons for the non-concordance. In particular, extensive simulations fail to find scenarios whereby positive selection can only be detected by either MK or PAML, but not both. Since molecular evolution is governed by positive and negative selection concurrently, a fundamental assumption for estimating one of these (say, positive selection) is that the other is constant. However, in a broad survey of primates, birds, Drosophila and Arabidopsis, we found that negative selection rarely stays constant for long in evolution. As a consequence, the variation in negative selection is often misconstrued as a signal of positive selection. In conclusion, MK, PAML and any method that examines genomic sequence evolution has to explicitly address the variation in negative selection before estimating positive selection. In a companion study, we propose a possible path forward in two stages—first, by mapping out the changes in negative selection and then using this map to estimate positive selection. For now, the large literature on positive selection between species has to await reassessment.     

师范大专生历史素养的现状及成因分析

通过问卷调查,指出了师范大专生历史素质的现状并就这些现状的成因进行了分析。为下一步解决这一问题提供了思考。     

博古学研究与欧洲近代早期自然史的复兴探析

博古学者对史料的搜集和整理,为后世史学家的深入研究提供材料,并使古希腊、古罗马时期探究事物的根本方法,即自然史在近代欧洲再次盛行。随着自然史的复兴,历史研究开始对知识本身有更深刻的诉求。博古学者借用自然史的方法,质疑古代作品的真实性,将实物史料中蕴含的经验知识纳入历史研究的范畴。学者们提高了对事实的敏感度,想象和虚构也变得不再容易,开始与古典史学那种修辞、演讲的功用有了明显的区分。     

解读近现代中国体育制度文化(一)——20世纪中国学校体育组织制度演变及其启示

学校体育组织制度是一个规定学校体育管理,规范学校体育行为的系统。通过文献资料法与历史学的研究,分析了中国学校体育组织制度演变并寻找演变过程中的特点,最后指出中国学校体育在20世纪的发展方向。     

解读近现代中国体育制度文化(二)——20世纪中国学校体育课程制度演变摭谈

学校体育课程是根据青少年的身心发展规律和要求,以发展学生体能、增进学生身心健康为目的而制订的,以体育运动为载体的学科知识体系。运用文献资料法,分析了20世纪中国学校体育课程制度的演变过程及其特点,指出:1、学校体育的发展必须与一定社会的政治、经济发展相一致;2、从全球化的视角指导体育文化的交融,以实现体育文化融合的中国化的过程;3、将政府和政党推动学校体育发展的外力转为广大人民群众的内在自觉行为,这才是推动学校体育不断发展的原动力。     

Exploring ancestral phenotypes and evolutionary development of the mammalian middle ear based on Early Cretaceous Jehol mammals

We report a new Cretaceous multituberculate mammal with 3D auditory bones preserved. Along with other fossil and extant mammals, the unequivocal auditory bones display features potentially representing ancestral phenotypes of the mammalian middle ear. These phenotypes show that the ectotympanic and the malleus-incus complex changed notably during their retreating from the dentary at various evolutionary stages and suggest convergent evolution of some features to extant mammals. In contrast, the incudomalleolar joint was conservative in having a braced hinge configuration, which narrows the morphological gap between the quadroarticular jaw joint of non-mammalian cynodonts and the incudomalleolar articulations of extant mammals. The saddle-shaped and abutting malleus-incus complexes in therians and monotremes, respectively, could have evolved from the braced hinge joint independently. The evolutionary changes recorded in the Mesozoic mammals are largely consistent with the middle ear morphogenesis during the ontogeny of extant mammals, supporting the relation between evolution and development.     

中国冰雪运动企业空间格局演化特征及影响因素研究

冰雪运动企业是冰雪运动产业蓬勃发展的重要载体,探究冰雪运动企业空间格局演化特征及影响因素,对于提升冰雪运动普及程度,促进区域冰雪运动产业集聚发展具有重要意义。以中国冰雪运动企业为研究对象,运用最近邻指数、标准差椭圆和核密度分析法,探索2000年、2005年、2010年、2015年和2020年中国冰雪运动企业的空间格局特征及演化趋势,并借助OLS模型解析影响冰雪运动企业空间布局的核心要素。结果表明:中国冰雪运动企业整体空间布局呈现集聚分布,向外扩散趋势不断减弱而集聚态势日益增强;中国冰雪运动企业分布的热点集聚区主要沿着“西南-东北”方向集中在东北地区、京津冀、长三角及珠三角地区,不同时间节点冰雪运动企业呈现不同分布密度;中国冰雪运动企业空间布局的形成是人口规模、经济实力、产业结构、政策支持、固定资产投资、消费需求、交通条件、雪场数量等多种要素综合作用的结果,且不同区位主导因素有所差异。最后,根据实证研究结论,提出相应对策性建议:借势北京冬奥会东风,冰雪运动产业聚焦空间布局、人才培养、政策扶持、产业融合、数字技术,推动产业高质量可持续发展。     

Natural selection contributes to the myopia epidemic

The prevalence of myopia, or nearsightedness, has skyrocketed in the past few decades, creating a public health crisis that is commonly attributed to lifestyle changes. Here we report an overall increase in the frequencies of myopia-associated mutant alleles over 25 years among participants of the UK Biobank. Although myopia itself appears to be selected against, many of the mutant alleles are associated with reproductive benefits, suggesting that reproduction-related selection inadvertently contributes to the myopia epidemic. We estimate that, in the UK alone, natural selection adds more than 100 000 myopia cases per generation, and argue that antagonistic pleiotropy be broadly considered in explaining the spreads of apparently disadvantageous phenotypes in humans and beyond.     

Early years teachers and the influence of Piaget: evidence from oral history

In studying the historical development of early years provision, a clear factor in raising its profile was the growth in scientific study of children, especially the reception and interpretation of Piaget's research. For an understanding of how the mediation of new thinking and new discoveries influenced students and teachers, textbooks provide an important documentary source, but evidence is also available through oral history in the living memories of practitioners themselves. This paper draws on the testimony of early years teachers who began their careers between 1927 and 1955 and continued teaching into the 1960s and 1970s. The account below begins with reflections on psychology and education in the early decades of the twentieth century drawn from a 1936 conference organised by the Nursery School Association of Great Britain, and from a widely used textbook that represents the gradual trend towards ‘fragmentation’ of educational theory into a multiplicity of disciplines. Reference is then made to two popular textbooks by prominent Froebelians, Brearley and Hitchfield, and by Ruth Beard illustrating the growing influence of Piaget as a post facto rationale for a pedagogy that was proceeding by instinct. Walkerdine, Lister and Hall are researchers who have investigated from various angles the impact of Piagetian psychology on primary practice, but the process whereby this translation from the laboratory to the classroom takes place is one that demands further investigation. Vital evidence lies in the living memories of early years teachers whose careers spanned the 1930s to the 1970s and a rich quality and personal texture of the data is apparent as retired early years teachers recounted their professional careers. It offers a more complex account than the grand narratives that historians have traditionally compiled from purely documentary evidence centring on great thinkers, key texts and policy initiatives. The role of in‐service education was clearly important in the experiences recalled in this paper. Above all we find evidence of a distinctive shift in teacher–child relationships over that historical period and of the contribution made to this by psychological theory, epitomised in the figure of Piaget and in his focus on the individual learner.     

英语学习趣味性初探

英语教学无论是“教”的难度还是“学”的困惑,都是毋庸置疑的。通过让学生了解所学语言的历史、语文化和其他与语言相关的诸多知识,提高语言学习的兴趣,从而实现学生快乐学习英语。