Patterns and rates of enamel growth in the molar teeth of early hominids

A recent study of the surface manifestation of incremental lines associated with enamel formation suggested that the crowns of early hominid incisor teeth were formed more rapidly than those of modern humans. In the absence of comparative data, the authors were forced to assume that enamel increments in fossil teeth were similar to those in modern humans. We have used evidence from the fractured surfaces of molar teeth to deduce estimates for both long- and short-period incremental growth markers within enamel in east African 'robust' australopithecine and early Homo teeth. We conclude that in these early hominids, crown formation times in posterior teeth, particularly in the large thick enamelled molar teeth of the east African 'robust' australopithecines, were shorter than those of modern humans. This evidence, considered together with data on crown and root formation times in modern apes, suggests that the posterior teeth in these hominids both formed and erupted more rapidly than those of modern man. These results have implications for attempts to assess dental and skeletal maturity in hominids.     

Ecological opportunity and sexual selection together predict adaptive radiation

A fundamental challenge to our understanding of biodiversity is to explain why some groups of species undergo adaptive radiations, diversifying extensively into many and varied species, whereas others do not. Both extrinsic environmental factors (for example, resource availability, climate) and intrinsic lineage-specific traits (for example, behavioural or morphological traits, genetic architecture) influence diversification, but few studies have addressed how such factors interact. Radiations of cichlid fishes in the African Great Lakes provide some of the most dramatic cases of species diversification. However, most cichlid lineages in African lakes have not undergone adaptive radiations. Here we compile data on cichlid colonization and diversification in 46 African lakes, along with lake environmental features and information about the traits of colonizing cichlid lineages, to investigate why adaptive radiation does and does not occur. We find that extrinsic environmental factors related to ecological opportunity and intrinsic lineage-specific traits related to sexual selection both strongly influence whether cichlids radiate. Cichlids are more likely to radiate in deep lakes, in regions with more incident solar radiation and in lakes where there has been more time for diversification. Weak or negative associations between diversification and lake surface area indicate that cichlid speciation is not constrained by area, in contrast to diversification in many terrestrial taxa. Among the suite of intrinsic traits that we investigate, sexual dichromatism, a surrogate for the intensity of sexual selection, is consistently positively associated with diversification. Thus, for cichlids, it is the coincidence between ecological opportunity and sexual selection that best predicts whether adaptive radiation will occur. These findings suggest that adaptive radiation is predictable, but only when species traits and environmental factors are jointly considered.     

经济全球化中的中非经贸现状与发展对策

中非各国同属发展中国家,在经济全球化进程中具有共同的政治经济利益。面对经济全球化对发展中国家特别是非洲各国经济的负面影响,中非各国应加强协作,大发展中非经贸合作,共同迎接全球化的挑战。本文通过分析经济全球化对非洲经济的负面影响及中非经贸发展现状,提出了在新形势下进一步加强中非经贸合作的对策。     

Growth processes in teeth distinguish modern humans from Homo erectus and earlier hominins.

A modern human-like sequence of dental development, as a proxy for the pace of life history, is regarded as one of the diagnostic hallmarks of our own genus Homo. Brain size, age at first reproduction, lifespan and other life-history traits correlate tightly with dental development. Here we report differences in enamel growth that show the earliest fossils attributed to Homo do not resemble modern humans in their development. We used daily incremental markings in enamel to calculate rates of enamel formation in 13 fossil hominins and identified differences in this key determinant of tooth formation time. Neither australopiths nor fossils currently attributed to early Homo shared the slow trajectory of enamel growth typical of modern humans; rather, both resembled modern and fossil African apes. We then reconstructed tooth formation times in australopiths, in the approximately 1.5-Myr-old Homo erectus skeleton from Nariokotome, Kenya, and in another Homo erectus specimen, Sangiran S7-37 from Java. These times were shorter than those in modern humans. It therefore seems likely that truly modern dental development emerged relatively late in human evolution.     

论《看不见的人》的布鲁斯表征

布鲁斯(blues)又称蓝调,是上世纪初期美国黑人创造的一种音乐样式。作为美国黑人种族文化的典型表征,布鲁斯是黑人文学文本研究的原始依据和文化源泉。文章通过对美国当代作家拉尔夫.埃利森的长篇小说《看不见的人》的布鲁斯表征的分析,指出作者将布鲁斯这一美国黑人独特的艺术形式与小说创作密切结合,体现了小说寻求自我身份认同的主题。     

成长的艰难——美国非洲裔作家成长小说中儿童成长的现实

从严格意义上讲,20世纪中期兴起的美国非洲裔文学思潮里,几乎没有专门的儿童文学作家。美国非洲裔作家们似乎也注意到这一点,因此,在他们的小说里,或多或少地都提到了美国黑人儿童成长所面临的问题,即面对残酷的种族歧视和压迫的现实,美国非洲裔儿童的成长之路异常艰难。     

Remains of Homo erectus from Bouri, Middle Awash, Ethiopia

The genesis, evolution and fate of Homo erectus have been explored palaeontologically since the taxon's recognition in the late nineteenth century. Current debate is focused on whether early representatives from Kenya and Georgia should be classified as a separate ancestral species ('H. ergaster'), and whether H. erectus was an exclusively Asian species lineage that went extinct. Lack of resolution of these issues has obscured the place of H. erectus in human evolution. A hominid calvaria and postcranial remains recently recovered from the Dakanihylo Member of the Bouri Formation, Middle Awash, Ethiopia, bear directly on these issues. These approximately 1.0-million-year (Myr)-old Pleistocene sediments contain abundant early Acheulean stone tools and a diverse vertebrate fauna that indicates a predominantly savannah environment. Here we report that the 'Daka' calvaria's metric and morphological attributes centre it firmly within H. erectus. Daka's resemblance to Asian counterparts indicates that the early African and Eurasian fossil hominids represent demes of a widespread palaeospecies. Daka's anatomical intermediacy between earlier and later African fossils provides evidence of evolutionary change. Its temporal and geographic position indicates that African H. erectus was the ancestor of Homo sapiens.     

悬崖与非悬崖生境下中华山蓼克隆整合能力及其表型差异比较

中华山蓼(Oxyria sinensis)是一种典型的根状茎型多年生草本,能在悬崖岩面上形成相当大的克隆。为了进一步了解中华山蓼在悬崖生境中的克隆生长特性及其对悬崖生境的适应对策,本研究比较了悬崖和非悬崖两种生境条件下生长的中华山蓼的克隆整合能力和形态可塑性,拟探讨如下问题:(1)中华山蓼是否具有克隆整合能力,如果有,其整合能力有多大?(2)中华山蓼在不同的生境条件下的克隆整合能力和形态上是否具有显著性差异?研究结果表明,中华山蓼具有克隆整合能力,但大多数的克隆其整合能力均不大。悬崖生境和非悬崖生境中的中华山蓼的整合能力之间没有显著性差异。中华山蓼在比叶面积、叶柄长、叶/叶柄生物量分配等性状上表现出了较强的可塑性,这些性状可能是中华山蓼对悬崖生境的适应对策之一。     

Earliest known simian primate found in Algeria.

The record of early fossil Simiiformes (Anthropoidea) from the Late Eocene and Early Oligocene of Africa and the Arabian Peninsula has increased dramatically in recent years. We report here the discovery of a new, diminutive and much older (Early or Middle Eocene) simian from an Algerian locality, Glib Zegdou. This species is smaller than any other living or fossil African simiiform. Derived similarities shared with Aegyptopithecus suggest that the new genus is more closely related to propliopithecines than to oligopithecines, implying that these two subfamilies differentiated during the Early Eocene. The new discovery confirms predictions about the great antiquity of Simiiformes and emphasizes a long and endemic African history for higher primates.     

南方稻区早籼新品种综合性状分析

以1998年和1999年南方水稻区域试验早籼早中熟组的数据为资料,采用朱军等[1,2]提出的统计分析方法分析产量、生育期、米质和抗性等性状的基因型×环境互作.方差分析结果表明,所有分析的性状都存在较大的年份效应,一些性状存在较大的基因型×年份互作效应.对产量和综合性状的比较表明:中组1号和湘早籼19产量较高.湘早籼19和351A/9279综合性状表现较好.此外还分析了各品种综合性状对环境指数的敏感程度和稳定性表现.     

Resolution of quantitative traits into Mendelian factors by using a complete linkage map of restriction fragment length polymorphisms

The conflict between the Mendelian theory of particulate inheritance and the observation of continuous variation for most traits in nature was resolved in the early 1900s by the concept that quantitative traits can result from segregation of multiple genes, modified by environmental effects. Although pioneering experiments showed that linkage could occasionally be detected to such quantitative trait loci (QTLs), accurate and systematic mapping of QTLs has not been possible because the inheritance of an entire genome could not be studied with genetic markers. The use of restriction fragment length polymorphisms (RFLPs) has made such investigations possible, at least in principle. Here, we report the first use of a complete RFLP linkage map to resolve quantitative traits into discrete Mendelian factors, in an interspecific back-cross of tomato. Applying new analytical methods, we mapped at least six QTLs controlling fruit mass, four QTLs for the concentration of soluble solids and five QTLs for fruit pH. This approach is broadly applicable to the genetic dissection of quantitative inheritance of physiological, morphological and behavioural traits in any higher plant or animal.     

麦洼牦牛184天乳量与相关性状的线性关系

对１３４头成年麦洼母牦牛犊牛初生重、最高月产奶量、乳脂率以及产犊前６个月时的体重、体高、体长、胸围、评分８个性状与１８４天产奶量的直线相关及上述８个性状与后者的偏回归和标准偏回归关系作了分析。结果显示，最高月产奶量与１８４天产奶量有明显的直线正向关系（ｐ＜０．０１），两者的偏回归关系为明显的同向绝对量增长态势（ｐ＜０．０１），前者对后者产生较大的正直接作用（ｐ＜０．０１），对后者的相对决定程度最高，是最为重要的早期选择性状。发现乳脂率与１８４天产奶量在线性范畴内相对独立，此结果区别于普通奶牛，可作为该二性状同时正向选择的科学依据，体重、体长、胸围分别与１８４天产奶量呈明显的正直线相关（ｐ＜０．０５或ｐ＜０．０１），可作为产奶量趋向性预测的早期信息。     

Late middle Eocene epoch of Libya yields earliest known radiation of African anthropoids

Reconstructing the early evolutionary history of anthropoid primates is hindered by a lack of consensus on both the timing and biogeography of anthropoid origins. Some prefer an ancient (Cretaceous) origin for anthropoids in Africa or some other Gondwanan landmass, whereas others advocate a more recent (early Cenozoic) origin for anthropoids in Asia, with subsequent dispersal of one or more early anthropoid taxa to Africa. The oldest undoubted African anthropoid primates described so far are three species of the parapithecid Biretia from the late middle Eocene Bir El Ater locality of Algeria and the late Eocene BQ-2 site in the Fayum region of northern Egypt. Here we report the discovery of the oldest known diverse assemblage of African anthropoids from the late middle Eocene Dur At-Talah escarpment in central Libya. The primate assemblage from Dur At-Talah includes diminutive species pertaining to three higher-level anthropoid clades (Afrotarsiidae, Parapithecidae and Oligopithecidae) as well as a small species of the early strepsirhine primate Karanisia. The high taxonomic diversity of anthropoids at Dur At-Talah indicates either a much longer interval of anthropoid evolution in Africa than is currently documented in the fossil record or the nearly synchronous colonization of Africa by multiple anthropoid clades at some time during the middle Eocene epoch.     

小麦品种川麦42×川农16重组自交系苗期叶片生长研究

川麦42是采用人工合成小麦首次培育成功的普通小麦推广品种,苗期表现强势生长．为弄清其遗传基础,评价其在小麦遗传改良中的利用价值,利用川麦42×川农16构建的127个重组自交系群体,对苗期叶长、叶宽、生长率等性状进行了研究．结果表明,各性状在RIL群体中呈连续分布,分布频率符合正态分布,同时存在双向超亲分离现象．相关性分析表明,叶长与小区产量、千粒重呈显著性相关,可作为品种早期初步选择的参考性状之一．     

Affinities of 'hyopsodontids' to elephant shrews and a Holarctic origin of Afrotheria

Macroscelideans (elephant shrews or sengis) are small-bodied (25-540 g), cursorial (running) and saltatorial (jumping), insectivorous and omnivorous placental mammals represented by at least 15 extant African species classified in four genera. Macroscelidea is one of several morphologically diverse but predominantly African placental orders classified in the superorder Afrotheria by molecular phylogeneticists. The distribution of modern afrotheres, in combination with a basal position for Afrotheria within Placentalia and molecular divergence-time estimates, has been used to link placental diversification with the mid-Cretaceous separation of South America and Africa. Morphological phylogenetic analyses do not support Afrotheria and the fossil record favours a northern origin of Placentalia. Here we describe fossil postcrania that provide evidence for a close relationship between North American Palaeocene-Eocene apheliscine 'hyopsodontid' 'condylarths' (early ungulates or hoofed mammals) and extant Macroscelidea. Apheliscine postcranial morphology is consistent with a relationship to other ungulate-like afrotheres (Hyracoidea, Proboscidea) but does not provide support for a monophyletic Afrotheria. As the oldest record of an afrothere clade, identification of macroscelidean relatives in the North American Palaeocene argues against an African origin for Afrotheria, weakening support for linking placental diversification to the break-up of Gondwana.     

基于密切值法的采场地压显现预警

为了有效地预警程潮铁矿采场地压显现的易发性状况,通过现场调研选取埋深、抗压强度和顶板管理等8种影响因素作为评价指标,利用变异系数法赋予各项评价指标的权重,基于密切值法理论建立采场地压显现预警模型。将此模型应用于程潮铁矿的油库和5-1工作面,通过分析密切值的大小预测程潮铁矿的油库和5-1工作面的易发性状况。结果表明:油库有低易发的危险; 5-1工作面有中易发的危险;该模型预警结果与实际状况相吻合。可见该方法有效可行,能够为矿山采场地压显现的预警提供有益的指导。     

The oldest known anthropoid postcranial fossils and the early evolution of higher primates

The middle Eocene primate family Eosimiidae, which is known from sites in central and eastern China and Myanmar, is central to efforts to reconstruct the origin and early evolution of anthropoid or 'higher' primates (monkeys, apes and humans). Previous knowledge of eosimiid anatomy has been restricted to the dentition and an isolated petrosal bone, and this limited anatomical information has led to conflicting interpretations of early anthropoid phylogeny. Here we describe foot bones of Eosimias from the same middle Eocene sites in China that yield abundant dental remains of this primate. Tarsals of Eosimias show derived anatomical traits that are otherwise restricted to living and fossil anthropoids. These new fossils substantiate the anthropoid status of Eosimias and clarify the phylogenetic position of anthropoids with respect to other major primate clades. Early anthropoids possessed a mosaic of primitive and derived traits in their postcranial skeletons, reflecting their derivation from haplorhine ancestors that retained many prosimian-like features.     

The bonobo genome compared with the chimpanzee and human genomes

Two African apes are the closest living relatives of humans: the chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus). Although they are similar in many respects, bonobos and chimpanzees differ strikingly in key social and sexual behaviours, and for some of these traits they show more similarity with humans than with each other. Here we report the sequencing and assembly of the bonobo genome to study its evolutionary relationship with the chimpanzee and human genomes. We find that more than three per cent of the human genome is more closely related to either the bonobo or the chimpanzee genome than these are to each other. These regions allow various aspects of the ancestry of the two ape species to be reconstructed. In addition, many of the regions that overlap genes may eventually help us understand the genetic basis of phenotypes that humans share with one of the two apes to the exclusion of the other.     

New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo

Since its discovery in 1972 (ref. 1), the cranium KNM-ER 1470 has been at the centre of the debate over the number of species of early Homo present in the early Pleistocene epoch of eastern Africa. KNM-ER 1470 stands out among other specimens attributed to early Homo because of its larger size, and its flat and subnasally orthognathic face with anteriorly placed maxillary zygomatic roots. This singular morphology and the incomplete preservation of the fossil have led to different views as to whether KNM-ER 1470 can be accommodated within a single species of early Homo that is highly variable because of sexual, geographical and temporal factors, or whether it provides evidence of species diversity marked by differences in cranial size and facial or masticatory adaptation. Here we report on three newly discovered fossils, aged between 1.78 and 1.95 million years (Myr) old, that clarify the anatomy and taxonomic status of KNM-ER 1470. KNM-ER 62000, a well-preserved face of a late juvenile hominin, closely resembles KNM-ER 1470 but is notably smaller. It preserves previously unknown morphology, including moderately sized, mesiodistally long postcanine teeth. The nearly complete mandible KNM-ER 60000 and mandibular fragment KNM-ER 62003 have a dental arcade that is short anteroposteriorly and flat across the front, with small incisors; these features are consistent with the arcade morphology of KNM-ER 1470 and KNM-ER 62000. The new fossils confirm the presence of two contemporary species of early Homo, in addition to Homo erectus, in the early Pleistocene of eastern Africa.