中国近代人群上颌前臼齿釉质-齿质连接面形状的三维几何形态测量

牙齿的釉质-齿质连接面(EDJ或Enamel-dentine junction)是釉质表面(OES或Outer enamel surface)形态的发生基础,其形态特征在牙齿发育早期形成,与遗传因素密切相关。为探讨EDJ形状在近代人群中的变异特点,本文使用显微断层扫描技术(micro-CT或micro-computed tomography)扫描了100例采自华中地区近代农业人群的上颌前臼齿(P~3和P~4各50例),并复原了EDJ表面三维结构。采用基于30个标志点(landmark)和半标志点(semi-landmark)的三维几何形态测量量化了上颌前臼齿EDJ表面形状。结果显示,牙齿内部舌侧尖区域变异程度较颊侧尖大。在人群内部,上颌前臼齿的变异方式主要表现在1)颊舌尖相互靠近或远离造成的咬合面深浅的差别;2)颊舌尖齿质最高点(dentine horn)相对高度的差异;3)舌侧尖近远中方向尺寸的变化;4)P~3颊侧尖近中脊的内收与外扩造成的整个轮廓形状的对称性变化;5)P~4整个咬合面轮廓MD/BL比值的大小差别。基于以上发现,本文进一步探讨了上颌前臼齿EDJ形状在两性或不同时代标本之间是否存在差异。平均形状的比较发现男性上颌前臼齿的舌尖相对较宽,颊侧尖近中脊相对较低。但主成分分析(Principal component analysis)和置换检验(Permutation test)显示两性差异未达到显著水平。同样,从新石器时代以来的各样本组之间在EDJ形状上的差别也没有达到统计上的显著水平。这一结果提示中国近代人群上颌前臼齿EDJ表面形状的变异特点至少可以追溯到全新世早期(本文使用标本最早来自距今6000-7000年前的新石器时代阶段)。未来EDJ的三维几何形态测量可通过扩大标本数量进一步探讨不同性别、不同地区人群、不同演化阶段之间的差异。     

禄丰古猿蝴蝶种下第四前臼齿釉质-齿质交界面的三维几何形态

禄丰古猿蝴蝶种 (Lufengpithecus hudienensis) 也称蝴蝶古猿,是重要的早期人科成员,化石产自云南元谋盆地竹棚-小河及雷老两个地点群,其年代为中新世晚期。上世纪八、九十年代的发掘工作共获得幼年个体颅骨1具、残上颌骨10件、残下颌骨17件及1500多枚单个牙齿。受限于当时的技术条件,蝴蝶古猿牙齿内部结构及三维形态一直未有报道和对比研究。本文首次使用高精度CT配合三维几何形态测量方法,对6枚产自小河地点的蝴蝶古猿下颌第四前臼齿的釉质-齿质交界面形态进行了观察和对比,对比材料包括步氏巨猿、猩猩（化石）、大猩猩、黑猩猩及现代人。多变量分析显示,蝴蝶古猿釉质-齿质交界面几何形态接近于本文所涉及的大型猿类对比标本,但并没有表现出与某一特定类群的相似性;咬合面轮廓狭长,前凹尺寸明显小于后凹;整体形态介于齿质尖较高的大猩猩和齿质尖较低、釉质-齿质交界面形态扁平的巨猿、猩猩和黑猩猩之间。本文所观察到的类群之间的异同可能与趋同演化有关,也需要更多数据的进一步验证。将釉质-齿质交界面的三维几何形态和其他牙齿内部结构的信息（如釉质厚度及其三维分布规律等）综合,有助于进一步讨论蝴蝶古猿的分类学、系统发育和食性。     

Tissue proportions and enamel thickness distribution in the early Middle Pleistocene human deciduous molars from Tighenif,Algeria

The present study of three human upper deciduous molars from the early Middle Pleistocene site of Tighenif, Algeria, constitutes the first microtomographic-based endostructural exploration of African fossil teeth likely representative of the Homo heidelbergensis morph. Comparative morphological observations and 2-3D measurements describing subtle tooth organization (crown tissue proportions) and enamel thickness topography (site-specific distribution and global patterning) indicate that their virtual extracted structural signature better fits the modern human, rather than the Neanderthal condition. Accordingly, we predict that the inner structural morphology of the deciduous molars from the Middle Pleistocene western European series better fits the primitive, and not the derived Neanderthal figures.     

Enamel-dentine junction (EDJ) morphology distinguishes the lower molars of Australopithecus africanus and Paranthropus robustus

Tooth crown morphology plays a central role in hominin systematics, but the removal of the original outer enamel surface by dental attrition often eliminates from consideration the type of detailed crown morphology that has been shown to discriminate among hominin taxa. This reduces the size of samples available for study. The enamel-dentine junction (EDJ) is the developmental precursor and primary contributor to the morphology of the unworn outer enamel surface, and its morphology is only affected after considerable attrition. In this paper, we explore whether the form of the EDJ can be used to distinguish between the mandibular molars of two southern African fossil hominins: Paranthropus (or Australopithecus) robustus and Australopithecus africanus. After micro-computed tomographic scanning the molar sample, we made high-resolution images of the EDJ and used geometric morphometrics to compare EDJ shape differences between species, in addition to documenting metameric variation along the molar row within each species. Landmarks were collected along the marginal ridge that runs between adjacent dentine horns and around the circumference of the cervix. Our results suggest that the morphology of the EDJ can distinguish lower molars of these southern African hominins, and it can discriminate first, second, and third molars within each taxon. These results confirm previous findings that the EDJ preserves taxonomically valuable shape information in worn teeth. Mean differences in EDJ shape, in particular dentine horn height, crown height, and cervix shape, are more marked between adjacent molars within each taxon than for the same molar between the two taxa.     

Occlusal surface pattern of the lower molars and the second deciduous molar among the living Polynesians

The occlusal surface pattern of the lower molars and the second deciduous molar among the Polynesians living in Western Samoa was studied on plaster casts. The following are the characteristic traits of this race. The occlusal surface pattern of the first and second lower molars falls within the range of variation of the Mongoloid racial group. In general, the variation of the furrow pattern is remarkable, but the tendency of reduction of number of cusps is not conspicuous. The frequency of C₆ in the lower molars and C₇ in m₂ is far higher than in any other population, but the frequency of C₇ in M₁ or M₂ is not noticeably different.     

A geometric morphometric analysis of hominin upper second and third molars, with particular emphasis on European Pleistocene populations

The study of dental morphology by means of geometric morphometric methods allows for a detailed and quantitative comparison of hominin species that is useful for taxonomic assignment and phylogenetic reconstruction. Upper second and third molars have been studied in a comprehensive sample of Plio- and Pleistocene hominins from African, Asian and European sites in order to complete our analysis of the upper postcanine dentition. Intraspecific variation in these two molars is high, but some interspecific trends can be identified. Both molars exhibit a strong reduction of the distal cusps in recent hominin species, namely European Homo heidelbergensis, Homo neanderthalensis and Homo sapiens, but this reduction shows specific patterns and proportions in the three groups. Second molars tend to show four well developed cusps in earlier hominin species and their morphology is only marginally affected by allometric effects. Third molars can be incipiently reduced in earlier species and they evince a significant allometric component, identified both inter- and intraspecifically. European Middle Pleistocene fossils from Sima de los Huesos (SH) show a very strong reduction of these two molars, even more marked than the reduction observed in Neanderthals and in modern human populations. The highly derived shape of SH molars points to an early acquisition of typical Neanderthal dental traits by pre-Neanderthal populations and to a deviation of this population from mean morphologies of other European Middle Pleistocene groups.     

东亚地区碳循环研究新进展

近百年来,温室效应的日益加剧,引发了全球温暖化、海平面上升等一系列重大环境问题,碳循环研究因此而受到全球范围的普遍关注和重视.东亚地区因其独特的气候特征,多样化的物种和生态系统,以及活跃的人类活动而成为世界碳循环研究中不可或缺的一部分.在中、日、韩三国联合启动东亚碳循环前沿研究计划(A3 Foresight Program)三周年之际,《中国科学生命科学》(Science China Life Sciences)2010年第7期发表了东亚地区碳循环研究专题,包括14篇述评和研究论文,从区域碳储量及其变化特征,不同地带森林生态系统的碳源汇变化,草地和农田生态系统的碳储量和碳循环研究中的新方法等多个方面系统展示了东亚地区碳循环研究的最新进展.     

早、中更新世中国古人类年代序列与区域演化特征

我国早、中更新世古人类和旧石器遗址蕴含着丰富的早期人类活动和生存环境的背景信息,建立精确的遗址年代序列是分析古人类活动的基础。近二十年来,旧石器时代考古和测年研究为建立我国早期人类活动的年代框架提供了丰富的材料。本文分析了目前我国已发表的95个有独立测年数据的早、中更新世遗址,将其纳入黄土-古土壤年代框架,初步建立自200多万年至末次间冰期的古人类活动年代序列,根据它们的时空分布,进一步阐释了古人类在不同区域活动强度演变的时空特征。总体来看,这些遗址在泥河湾-周口店、秦岭山地、长江下游及长江流域以南(南方)四大区域呈现出聚集分布的特征;区域古人类活动强度主要表现在从早更新世的泥河湾-周口店、中更新世的秦岭山地、到中更新世晚期的长江中下游和南方区域的时空序列上。此外,仍有较多已发掘遗址缺少年代研究或存在测年问题,今后需要加强遗址的精确测年研究。     

Non-occlusal dental microwear variability in a sample of Middle and Late Pleistocene human populations from Europe and the Near East

Non-occlusal, buccal tooth microwear variability has been studied in 68 fossil humans from Europe and the Near East. The microwear patterns observed suggest that a major shift in human dietary habits and food processing techniques might have taken place in the transition from the Middle to the Late Pleistocene populations. Differences in microwear density, average length, and orientation of striations indicate that Middle Pleistocene humans had more abrasive dietary habits than Late Pleistocene populations. Both dietary and cultural factors might be responsible for the differences observed. In addition, the Middle Paleolithic Neanderthal specimens studied show a highly heterogeneous pattern of microwear when compared to the other samples considered, which is inconsistent with a hypothesis of all Neanderthals having a strictly carnivorous diet. The high density of striations observed in the buccal surfaces of several Neanderthal teeth might be indicative of the inclusion of plant foods in their diet. The buccal microwear variability observed in the Neanderthals is compatible with an overall exploitation of both plant and meat foods on the basis of food availability. A preliminary analysis of the relationship between buccal microwear density and climatic conditions prevailing in Europe during the Late Pleistocene has been attempted. Cold climatic conditions, as indicated by oxygen isotope stage data, seem to be responsible for higher densities of microwear features, whereas warmer periods could correspond to a reduced pattern of scratch density. Such a relationship would be indicative of less abrasive dietary habits, perhaps more meat dependent, during warmer periods.