南京2号人类头骨化石的复位和形态

南京2号人类头骨化石仅保留部分的额骨、顶骨、枕骨和颞骨,为一不完整的颅盖骨。其顶骨和枕骨有数条断裂缝,各断块之间有程度不一的错动,致使该颅盖骨显得外形异常。本项研究是对该颅盖骨的错动部分进行复位,结果表明,南京2号头骨有较大的顶骨、较小的上枕鳞相对宽度、可能较大的颅容量。这些形态提示该头骨与直立人有所不同而与早期智人相近。该头骨所具有的角圆枕、颞鳞顶缘形状、枕骨圆枕发育程度、枕骨的枕平面与项平面过渡情况、枕内隆突点与枕外隆突点的距离、头骨骨壁厚度、脑膜中动脉分支情况、头骨枕面观之轮廓线样式等形态细节,还很难作为可靠的依据把南京2号头骨鉴定为直立人。南京2号头骨很大可能是属于智人亚种(Homo sapiens sapiens)中的一员。     

南京人头骨化石研究新进展

1 993年在南京汤山葫芦洞发现了2具人类头骨化石-南京1号头骨和南京2号头骨.这2具头骨化石先后经过两次研究都被认为是属于直立人.近几年来,对南京人类头骨化石作了更深入的研究,研究涉及的内容可归纳为:1)对南京2号头骨作了复位和复原、进行了重新鉴定.对南京1号头骨作了颅容量计算;2)对南京1号头骨作了更广泛的比较,对比标本包括周口店直立人头骨、印尼Sangiran 17直立人头骨、肯尼亚KNM-ER3733头骨和东非Bodo头骨;3)对南京1号头骨的适应性特征-鼻梁高耸进行了论证.这些研究的结果表明:1)南京2号头骨应属于早期智人而不是直立人.南京1号头骨的颅容量,经计算,为871 ml.该颅容量与周口店3号头骨的相当,二者年代也应相近(周口店3号头骨的年代为57.8万年);2)南京1号头骨显示出地区性的形态特征.提示了中国人群南北两大类型的形态差别早在南京直立人生活时期已显出端倪.南京1号头骨及和县头骨可能代表一类中国南方的直立人群,其形态与以周口店直立人为代表的中国北方直立人群有些不同.南京1号头骨在脑颅上显示出较多的与KNM-ER 3733头骨相近的特征,但在面颅上二者相差较大,提示了直立人某些成员在至少1Ma期间脑颅形态保持稳定.南京1号头骨与Bodo头骨的比较结果与"中心和边缘"假说的推测相符合,在东亚这个"边缘地区",现代人群的面颅测量性特征可追溯到直立人群那里;3)南京直立人的高耸鼻梁是适应性特征,是对寒冷或(和)干燥气候适应的结果,并不意味着"西方血统".     

Development and tissue origins of the mammalian cranial base

The vertebrate cranial base is a complex structure composed of bone, cartilage and other connective tissues underlying the brain; it is intimately connected with development of the face and cranial vault. Despite its central importance in craniofacial development, morphogenesis and tissue origins of the cranial base have not been studied in detail in the mouse, an important model organism. We describe here the location and time of appearance of the cartilages of the chondrocranium. We also examine the tissue origins of the mouse cranial base using a neural crest cell lineage cell marker, Wnt1-Cre/R26R, and a mesoderm lineage cell marker, Mesp1-Cre/R26R. The chondrocranium develops between E11 and E16 in the mouse, beginning with development of the caudal (occipital) chondrocranium, followed by chondrogenesis rostrally to form the nasal capsule, and finally fusion of these two parts via the midline central stem and the lateral struts of the vault cartilages. X-Gal staining of transgenic mice from E8.0 to 10 days post-natal showed that neural crest cells contribute to all of the cartilages that form the ethmoid, presphenoid, and basisphenoid bones with the exception of the hypochiasmatic cartilages. The basioccipital bone and non-squamous parts of the temporal bones are mesoderm derived. Therefore the prechordal head is mostly composed of neural crest-derived tissues, as predicted by the New Head Hypothesis. However, the anterior location of the mesoderm-derived hypochiasmatic cartilages, which are closely linked with the extra-ocular muscles, suggests that some tissues associated with the visual apparatus may have evolved independently of the rest of the “New Head”.     

Ossification of the human fetal basicranium

Previous investigations of prenatal development of the human cranium have not identified the sequence of its ossification. The purpose of the present study was to elucidate the pattern of skeletal maturity of the cranial bones in the midsagittal region anterior to the foramen magnum. This study is based upon a radiographic and histochemical investigation of midsagittal tissue blocks of the cranial bases of 73 human fetuses derived from the first half of the prenatal period. A marked regularity in the ossification pattern of the bones in the midsagittal part of the human cranium was observed. Ossification starts in the frontal bone. The sequence in which the next bones ossify is occipital bone, basisphenoid bone, presphenoid bone, and ethmoid bone. The material was divided into 7 maturity stages devised for this analysis. The stages were related to general fetal size (crown-rump length) and to general fetal maturation (composite number of ossified bones in hand and foot). Skeletal development of the median part of the human cranium is not strictly correlated with the size or the stage of general maturation of the fetuses. Knowledge of normal skeletal development is necessary for understanding anomalies of development.     

Activation of FGF signaling mediates proliferative and osteogenic differences between neural crest derived frontal and mesoderm parietal derived bone

Background

As a culmination of efforts over the last years, our knowledge of the embryonic origins of the mammalian frontal and parietal cranial bones is unambiguous. Progenitor cells that subsequently give rise to frontal bone are of neural crest origin, while parietal bone progenitors arise from paraxial mesoderm. Given the unique qualities of neural crest cells and the clear delineation of the embryonic origins of the calvarial bones, we sought to determine whether mouse neural crest derived frontal bone differs in biology from mesoderm derived parietal bone.

Methods

BrdU incorporation, immunoblotting and osteogenic differentiation assays were performed to investigate the proliferative rate and osteogenic potential of embryonic and postnatal osteoblasts derived from mouse frontal and parietal bones. Co-culture experiments and treatment with conditioned medium harvested from both types of osteoblasts were performed to investigate potential interactions between the two different tissue origin osteoblasts. Immunoblotting techniques were used to investigate the endogenous level of FGF-2 and the activation of three major FGF signaling pathways. Knockdown of FGF Receptor 1 (FgfR1) was employed to inactivate the FGF signaling.

Results

Our results demonstrated that striking differences in cell proliferation and osteogenic differentiation between the frontal and parietal bone can be detected already at embryonic stages. The greater proliferation rate, as well as osteogenic capacity of frontal bone derived osteoblasts, were paralleled by an elevated level of FGF-2 protein synthesis. Moreover, an enhanced activation of FGF-signaling pathways was observed in frontal bone derived osteoblasts. Finally, the greater osteogenic potential of frontal derived osteoblasts was dramatically impaired by knocking down FgfR1.

Conclusions

Osteoblasts from mouse neural crest derived frontal bone displayed a greater proliferative and osteogenic potential and endogenous enhanced activation of FGF signaling compared to osteoblasts from mesoderm derived parietal bone. FGF signaling plays a key role in determining biological differences between the two types of osteoblasts.     

A tale of two cities: The genetic mechanisms governing calvarial bone development

The skull bones must grow in a coordinated, three‐dimensional manner to coalesce and form the head and face. Mammalian skull bones have a dual embryonic origin from cranial neural crest cells (CNCC) and paraxial mesoderm (PM) and ossify through intramembranous ossification. The calvarial bones, the bones of the cranium which cover the brain, are derived from the supraorbital arch (SOA) region mesenchyme. The SOA is the site of frontal and parietal bone morphogenesis and primary center of ossification. The objective of this review is to frame our current in vivo understanding of the morphogenesis of the calvarial bones and the gene networks regulating calvarial bone initiation in the SOA mesenchyme.     

Relationships between growth at the sutures of the rabbit calvarium

The present study was designed to elucidate the relationships between growth increments at the cranial vault sutures in rabbits. Thirteen male New Zealand white rabbits were followed regularly from age 31 to 142 days using a roentgen stereophotogrammetric system. Spherical tantalum markers were implanted into the nasal, frontal, and parietal bones, and implant stability was checked at each stereo examination. Problems with instability were encountered only in the nasal bones. Registered growth rates conformed to our previous investigations. High correlations were observed between the following areas; the coronal suture to the frontonasal suture, the first principal component of the neurocranial suture group to the frontonasal suture, and the principal component of the craniofacial suture group to the coronal suture. Remaining relationships demonstrated dispersion to various extents. The findings indicate that there seems to exist a basic mutual dependence between neural and facial skeletal growth, as well as complex covariations between the various sutures of the rabbit calvarium.     

Radiographic determination of prenatal basicranial ossification

In a previous investigation on prenatal development of the human cranial base, the sequence in which the bones develop in the midsagittal region was elucidated. The purpose of the present study was to identify fetal ossification on horizontal plane roentgenograms of the occipital and sphenoid bones in the central part of the cranial base, and establish stages in bone appearance related to general fetal developmental parameters. This study is based upon roentgenograms of the cranial base of 145 human fetuses from the first half of the prenatal period. Two different maturation patterns of the sphenoid bone were observed. The first, most common pattern is characterized by a midsagittal centre of ossification and the second by bilateral centres of ossification in the corpus of the sphenoid bone. These bilateral centres might in some cases be connected by a slight bony bridge. It appears that these different maturation patterns are maintained throughout the period investigated. The material was divided into five well-defined developmental stages for both maturation patterns and general parameters of fetal development. Mapping different aspects of ossification in normal cranial development is necessary for understanding deviations of cranial maturation and growth.     

南京1号直立人头骨与肯尼亚KNM-ER 3733人类头骨化石的形态比较

KNM-ER 3733人类头骨化石的年代为距今1.78百万年,1975年发现于肯尼亚。Walker和Leakey注意到这具头骨与周口店直立人的在脑颅形态上很相近,但二者在年代上相差大约1百万年,故认为直立人形态在这1百万年期间是稳定的。长期来此观点缺乏更多的人类化石证据来支持。1993年在中国发现了南京1号人类头骨化石。该头骨与KNM-ER 3733头骨一样兼具脑颅和面颅,且都属于成年女性个体,但南京1号人类头骨化石的年代比KNM-ER 3733人类头骨化石的要晚大约1百万年。因此,南京1号人类头骨是目前所知的可用来验证直立人头骨形态是否在1百万年期间保持稳定的唯一合适的人类头骨化石材料。形态比较表明,这两个人类头骨化石的脑颅虽然在眶上圆枕上沟的发育程度、眶后收缩的程度、额骨横向隆起的程度、角圆枕和乳后突的发育与否、顶骨形状以及骨壁厚度的表现上有所差异,但有更多的形态性状显示出相近。这些相近表现在脑颅的长、宽、高值上;颅容量上;脑颅的低矮性上;脑颅最大宽之位置上;额骨、顶骨、枕骨之矢弧值的比例上;眶上圆枕的纤细上;顶骨的大小和矢向扁平性上;颞线位置和颞鳞顶缘的形状上;枕鳞的低宽形状上;上枕鳞与下枕鳞之间的转折形状和比例上;枕骨圆枕和枕骨圆枕上沟的发育程度上等。这两具头骨的面颅虽然有同属突颌型的面角、皆发育有鼻骨间嵴、两鼻骨组成的上部宽度与下部宽度皆差别很大,但有更多的形态性状显示出差别。这些差别表现在面型上、颜面上部扁平度上、眶形和眶型上、上颌额突外侧面的朝向上、鼻骨横向隆起程度上、鼻梁外突程度上、鼻型上、颧骨下缘外展程度上、颊高上、颧上颌下缘的形状上、上颌颧突基部的位置上以及颧结节的位置上等。因此,南京1号头骨与KNM-ER 3733头骨之间在脑颅上显示出较多的相近性状,在面颅上则显示出较多的相异性状。脑颅方面的相近性状大多具有分类上的鉴别价值。这两个头骨脑颅形态的相近支持把KNM-ER 3733头骨鉴定为"直立人"的观点;也提示了南京1号头骨的脑颅似乎保持着1百多万年前的"祖先"形态。如果直立人的某些成员在至少1百万年期间保持着形态稳定的话,则这种形态上的稳定主要是表现在脑颅形态上。这两具头骨的面颅形态上较大差异的意义,目前尚不清楚。     

Reconstructing cranial evolution in an extinct hominin

Homo erectus is the first hominin species with a truly cosmopolitan distribution and resembles recent humans in its broad spatial distribution. The microevolutionary events associated with dispersal and local adaptation may have produced similar population structure in both species. Understanding the evolutionary population dynamics of H. erectus has larger implications for the emergence of later Homo lineages in the Middle Pleistocene. Quantitative genetics models provide a means of interrogating aspects of long-standing H. erectus population history narratives. For the current study, cranial fossils were sorted into six major palaeodemes from sites across Africa and Asia spanning 1.8–0.1 Ma. Three-dimensional shape data from the occipital and frontal bones were used to compare intraspecific variation and test evolutionary hypotheses. Results indicate that H. erectus had higher individual and group variation than Homo sapiens, probably reflecting different levels of genetic diversity and population history in these spatially disperse species. This study also revealed distinct evolutionary histories for frontal and occipital bone shape in H. erectus, with a larger role for natural selection in the former. One scenario consistent with these findings is climate-driven facial adaptation in H. erectus, which is reflected in the frontal bone through integration with the orbits.     

华北人欧洲人和澳洲土著人的头骨厚度

The thickness of the cranial vault at the midline on the mid-frontal squama, pre-bregmatic einence, frontal at bregma, parietal at vertex, occipital at lambda and the external occipita1 protuberance was recorded in 40 male and 7 female Northern Chinese crania, 47 male and 52 female Australian Aboriginal crania and 13 male European crania using specially nodified vernier calipers. Comparison of vault thickness data obtained through direct measurement with those obtained fron lateral radiographs indicated that direct measurenent provided consistently more accurate results.
Male and fermale samples were processed separately so that the extent of sexbased variation could be examined.Student's t test was used to compare the sample means and the percentage of sexual dimorphism for each dimension was calculated according to Garn et al, (1964).The possibility of an allometric association between the thickness of the bones within the cranial vault, size of the cranial vault and stature was examined using Spearman's rank correlation coefficient and the Australian Aboriginal sample.
All but one of the mean thickness dimensions in the Australian Aboriginal male sample is significantly greater than the Northern Chinese and European means. The female results support those obtained with the males.In both males and females thickness at the external occipital protuberance, in all of the populations examined,did not correlate highly with that obtained from other parts of the cranial vault.This reflects the high degree of morphological variation in the position of the internal occipital protuberance and its influence on cranial vault thickness dimensions recorded at the external occipital protuberance.The European and Northern Chinese samples have similar cranial vault thickness dimensions. The Spearman's rank correlation coefficient matrix scores provide sone support for a biological association between vault thickness and overall cranial size. However, there appears to be little support for an association between stature and cranial vault thickness. The difference between the male and female mean vault thickness dimensions were significant at bregma, vertex and the external occipital protuberance in Australian Aboriginals and lambda and the external occipital protuberance in Northern Chinese. Some caution is needed in the interpretation of the Northern Chinese female data as the sample is extremely small.
Evidence of trauma, supressed fractures, is extremely common on the vaults of Australian Aboriginal crania from southern and central Australia. Traditionally Australian Aboriginals, males and females, involved in agressive dispute will use a substantial wooden implement and strike to the head of thir opponent(Meggitt 1962).The injuries that result from this are more common in females than in male. This form of social interaction must have rigorously selected against those individuals with thinner bones in their cranial vaults. To a large degree this may explain the greatly thickened vaults in Australian Aboriginals relative to Europeans and Northern Chines.This may also provide a clue to the factors resulting in the development of marked cranial vault thickness in Homo erectus.
     

Patterning of geographic variation in Middle Pleistocene Homo frontal bone morphology

A quantitative assessment of the frontal bone morphology of a sample of Middle Pleistocene hominins was undertaken in order to address questions regarding their population structure and evolutionary history. Outline tracings of the frontal bones of forty-seven fossil crania were obtained, and size-standardized measurements were then computed using an Elliptical Fourier analysis of these tracings. Principal component scores of the Fourier harmonic amplitudes were derived and served as a quantitative representation of the morphology of the frontal bone. Morphological, geographical, and temporal distance matrices were then constructed between each pair of fossils. A partial Mantel matrix correlation test was performed between morphological and geographical distance matrices, controlling for temporal distance, in order to determine if the pattern of geographical differentiation in features of the frontal bone of mid-Pleistocene Homo followed that of an isolation-by-distance model of population structure. The results of the partial Mantel tests indicate that the overall patterning of differentiation in the features of the frontal bone cannot best be explained by a population structure shaped by isolation-by-distance. Additionally, various aspects of the frontal bone quantified here follow different patterns of geographical differentiation, suggesting that a mosaic pattern of evolution holds true for characters within one cranial region and not just for those between regions.     

Thickness distribution of the occipital bone--a new approach based on CT-data of modern humans and OH 9 (H. ergaster)

A new approach for the analysis of cranial bone thickness is introduced. The study focuses on the occipital bone of modern humans and of a 1.25 Myr-old H. Ergaster/erectus specimen from Olduvai Gorge (OH 9). A semiautomatic algorithm detects a multitude of thicknesses from CT-data of the investigated bones. We find that every bone is characterized by its own distribution pattern of cranial thickness, which is then analyzed statistically. The results demonstrate that the thickness distribution of the occipital bone of OH 9 is within the normal range of the H. sapiens sample (which itself shows a remarkably high variance). This contributes to a further analysis of phyletic differences of hominid morphology by including distribution patterns of thickness combined with aspects of functional anatomy.     

Congruence of individual cranial bone morphology and neutral molecular affinity patterns in modern humans

Recent studies have demonstrated that the shape of the human temporal bone is particularly strongly correlated with neutral genetic expectation, when compared against other cranial regions, such as the vault, face, and basicranium. In turn, this has led to suggestions that the temporal bone is particularly reliable in analyses of primate phylogeny and human population history. While several reasons have been suggested to explain the temporal bone's strong fit with neutral expectation, the temporal bone has never systematically been compared against other individual cranial bones defined using the same biological criteria. Therefore, it is currently unknown whether the shapes of all cranial bones possess reliable information regarding neutral genetic evolution, or whether the temporal bone is unique in this respect. This study tests the hypothesis that the human temporal bone is more congruent with neutral expectation than six other individual cranial bones by correlating population affinity matrices generated using neutral genetic and 3D craniometric data. The results demonstrate that while the temporal bone shows the absolute strongest correlation with neutral genetic data compared with all other bones, it is not statistically differentiated from the sphenoid, frontal, and parietal bones in this regard. Potential reasons for the temporal bone's consistently strong fit with neutral expectation, such as its overall anatomical complexity and/or its contribution to the architecture of the basicranium, are examined. The results suggest that future phylogenetic and taxonomic studies would benefit from considering the shape of the entire cranium minus those regions that deviate most from neutrality. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Distinct spatiotemporal roles of hedgehog signalling during chick and mouse cranial base and axial skeleton development

The cranial base exerts a supportive role for the brain and includes the occipital, sphenoid and ethmoid bones that arise from cartilaginous precursors in the early embryo. As the occipital bone and the posterior part of the sphenoid are mesoderm derivatives that arise in close proximity to the notochord and floor plate, it has been assumed that their development, like the axial skeleton, is dependent on Sonic hedgehog (Shh) and modulation of bone morphogenetic protein (Bmp) signalling. Here we examined the development of the cranial base in chick and mouse embryos to compare the molecular signals that are required for chondrogenic induction in the trunk and head. We found that Shh signalling is required but the molecular network controlling cranial base development is distinct from that in the trunk. In the absence of Shh, the presumptive cranial base did not undergo chondrogenic commitment as determined by the loss of Sox9 expression and there was a decrease in cell survival. In contrast, induction of the otic capsule occurred normally demonstrating that induction of the cranial base is uncoupled from formation of the sensory capsules. Lastly, we found that the early cranial mesoderm is refractory to Shh signalling, likely accounting for why development of the cranial base occurs after the axial skeleton. Our data reveal that cranial and axial skeletal induction is controlled by conserved, yet spatiotemporally distinct mechanisms that co-ordinate development of the cranial base with that of the cranial musculature and the pharyngeal arches.     

The effects of experimental unilateral anotia on skull development in the chick embryo. III. Chondrocranial development in anotic embryos of 7-20 days of incubation.

The study of the development of of the chondrocranium in chick embryos with unilateral (right-sided) anotia revealed the following main characteristics. 1. The median axes of the chordal and the prechordal part of the cranial base are not in a straight line but show a deviation toward the right side. The angle between the two axes has its vertex in the region of the foramen hypophyseos. 2. The metotic cartilage and the foramina of the IXth and Xth cranial nerves are normal in position. 3. The tectum synoticum develops later and to a lesser extent than normal. 4. Between the basal plate, the metotic cartilage, the occipital arch and the supracapsular cartilage a foramen is formed which, later in development, is closed by outgrowths of the metotic cartilage and the basal plate. 5. The "optic area" shows a practically normal appearance which indicates that the cartilaginous ventral wall of the lagenal capsule is of basal plate origin. 6. The pro-otic process develops practically normal and, hence, is independent of the ear capsule. 7. The quadrate cartilage and the right lower jaw are displaced ventro-posteriorward. The earliest development of the perichondral bones shows some particularities which are closely correlated with the development of the various cartilaginous structures.     

Kinematics of cranial vault growth in rabbits

To characterize mathematically the spatial rearrangement of cranial vault bones of the rabbit during growth, a longitudinal study was undertaken from age 4-20 weeks. Initially, at least three nonlinear tantalum bone markers were implanted in the parietal, frontal, and the combined nasal bones. Thereafter, the animals were followed regularly with roentgen stereophotogrammetrical analysis. The parietal bones were found to rotate laterally upward (3 degrees), while the frontal bones rotated downward (2 degrees) relative to their contralaterals. The frontal bones rotated rostrally upward (12 degrees) and outward (3 degrees) as well as laterally downward (5 degrees) in relation to the parietal bones. Due to the morphology of the rabbit head, the examination positioning used in this study, and the direction of the growth process, growth at the coronal suture correlated fairly well with longitudinal axis translations; but the growth at the frontonasal suture relative to the frontal bones was directed about 45 degrees downward. This points to the importance of the bone-marker positioning, so that their connecting line is directed along the axis of growth. Also, this approach makes it possible to obtain new information on the development and treatment of craniofacial aberrations.     

安徽东至华龙洞出土的人类化石

2006年在安徽省东至县华龙洞发现了1枚人类下颌第二臼齿和2件可以拼接在一起的额骨碎片化石。根据华龙洞动物群组成及地层情况,初步确定华龙洞化石层的时代为更新世中期。本文对在华龙洞发现的人类头骨和牙齿化石的形态特征进行了观测,并与相关古人类标本进行了对比。研究发现:华龙洞人额骨和下颌臼齿都呈现出一系列常见于东亚直立人的特征。华龙洞额骨曲度较小,具有粗壮的颞线和较厚的骨壁。此外,华龙洞额骨还具有额中缝结构和扩大的额窦。华龙洞下颌第二臼齿总体显得比较粗壮。齿冠咬合面具有第五尖、第六尖和第七尖。齿冠尺寸明显大于早期现代人、现代人类和欧洲更新世中期人类,位于直立人变异范围。结合对华龙洞人类额骨和牙齿形态对比所揭示的形态特点,在华龙洞发现的人类化石可能代表着生活在更新世中期的直立人。