东胡林4号人牙齿形态特征观察

北京门头沟区斋堂镇东胡林遗址是重要的新石器时代早期遗址。本文描述了东胡林4号人(14C年龄约为8540aBP., 树轮校正年龄约为7500aBC.) 的上颌牙、下颌牙21枚。多数牙齿重度磨耗, 意味着当时人类处于狩猎—采集经济时代, 食物结构可能主要以坚硬食物(如朴树果核) 或高纤维食物为主。上第三臼齿退化缩小, X光透视检查为东胡林人下第三臼齿阻生提供了确凿无疑的证据。在4枚牙齿上发现龋洞, 其中左上第一臼齿、第二臼齿的龋蚀已破坏牙本质全层。严重的龋齿病揭示了东胡林4号人的口腔状态, 在一定程度上可能与经常性地摄取富含碳水化合物的食物有关。     

“北京人”大事记（1918—1989）

1918年春,中国农商部矿业顾问、瑞典地质学家安特生(J.G.Anderson)博士在北京周口店查勘煤矿地质时,于周口店西南约二公里的“鸡骨山”的一个石灰岩裂隙中,发现和采集了一批小型哺乳类动物化石,其中多数是啮齿类,此地即后来的第6化石地点。1921年安特生同美国古生物学家谷兰阶(WalterGranger)及奥地利师丹斯基(O.Zdan sky)再次来到周口店。在采石工人的指引下,在鸡骨山之北2公里的龙骨山北坡发现了后来被称为“北京人化石产地”的周口店第1地点。1923年,师丹斯基在龙骨山试掘,发现了已磨损的人类左上臼齿一枚,他把其他尚待整理的化石全部     

云南禄丰晚中新世古猿地点的仓鼠类化石

述了采自云南禄丰晚中新世石灰坝组的仓鼠类化石—新种──Kowalskiahanaesp.nov.。后脊Ⅱ和三齿根在M1中所占的比例、第一臼齿前边尖的宽度以及第三臼齿的退化程度表明,新种的演化水平与欧洲瓦里士晚期或土洛里早、中期的K.schaubi,K.fahlbuschi和K.skofleki接近,它是我国现知科氏仓鼠属中构造最原始的一种。     

新发现的一颗庙后山人的臼齿

在《庙后山——辽宁省本溪市旧石器文化遗址》一书中记述了人类犬齿、右下臼齿各一枚;本文现补记庙后山人牙的第三颗,也就是右上第三臼齿。 1979年春,天津自然博物馆古人类组应邀参加庙后山遗址发掘工作,曾搜集一些动物化石标本,主要是单个兽牙。笔者之一(林)于1985年6月间至天津自然博物馆,认出这颗人牙。     

横断山区高山姬鼠臼齿特征的研究

高山姬鼠Apodemus chevrieri分布在横断山及其附近地区。臼齿在动物的生存和生态适应中起着重要的作用。为探讨横断山环境对高山姬鼠臼齿表型变异的影响,本研究采用几何形态测量法对横断山由北到南(东北:巴塘;中部:中甸和宁蒗;南部:景东)分布的高山姬鼠的上臼齿(第一上臼齿、第二上臼齿、第三上臼齿)和下臼齿(第一下臼齿、第二下臼齿、第三下臼齿)进行测量,并进行主成分分析、薄片样条分析和多维尺度分析。研究结果表明,横断山高山姬鼠各地理种群间的臼齿有一定形态变异,薄片样条法分析显示各臼齿齿叶间有一定的形变发生,这可能与高山姬鼠在横断山各地区生存环境有关。     

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。     

广西扶绥南山洞新发现的人类化石和蒙古野驴化石——末次冰期华南气候变化的哺乳动物化石新证据

广西扶绥县南山洞发现人类化石及哺乳动物化石。人类化石包括2枚智人牙齿化石,分别是左下第三臼齿和右下第二臼齿,其形态特征与广西其他山洞发现的智人化石相似,归入晚期智人。哺乳动物化石多为华南大熊猫———剑齿象动物群成员,时代属更新世晚期。该地点新发现的蒙古野驴化石属华南晚更新世动物群的首次发现。南山洞所有化石发现于洞内浅褐色砂质粘土中,堆积物第二层钙板层的铀系年龄为30—40ka。蒙古野驴的出现暗示中国南方大陆可能在末次冰期出现过干冷的气候环境。     

元谋古猿下颌臼齿三维立体特征

采用欧氏距离矩阵分析（EDMA）方法对72枚元谋古猿及作为对比样本的10枚禄丰古猿、现生大猿类和人类下颌臼齿齿冠13个测量标志点三维测量数据的统计分析显示：元谋古猿在下颌臼齿齿冠三维形态测量特征上与禄丰古猿最为接近。与现生大猿类及人类相比,元谋古猿和禄丰古猿均与人类之间呈现出非常显著的差异,而与猿类较为接近。它们两者及生大猿类均与人类之间具有许多共同的差异表现特点。元谋古猿在下颌臼齿三维测量特征方面与三种现生大猿类各自之间的差别表现相似。其中,元谋古猿与猩猩之间的牙齿形态特征上似乎更为接近。但目前对这些特征相似差异的含义尚难以确定。     

浙江菱湖一亚洲象臼齿的记述

1978年5月,浙江吴兴县文管会赠给我馆一个象的臼齿化石。随即笔者到化石产地——菱湖镇郊杨介巷大队了解。化石是在距地面3米左右的地层中发现的。这是一个亚洲象(Elephas maxi-mus)的第三右下臼齿,牙齿保存基本完整,现记述如下:     

中国人牙齿形态测量分析——华北近代人群臼齿齿冠及齿尖面积

本文采用数字摄影和图像分析技术对华北新石器时代人类上、下颌臼齿齿冠及齿尖基底面积进行了精确测量。在此基础上, 计算了相对齿尖基底面积。结果显示: 近代华北人上颌各臼齿齿尖大小均呈原尖>前尖>后尖>次尖的顺序, 下颌三个臼齿齿尖大小面积顺序有所不同; 上颌的后尖和次尖呈现异速生长的趋势。各臼齿齿尖相对面积的总体变异呈下颌臼齿大于上颌臼齿、M1到M3依次增加、靠近远中侧的齿尖大于近中侧的齿尖的趋势。本文首次对现代中国人臼齿相对齿尖面积进行了调查统计, 为古人类学及体质人类学研究积累了基础性数据。本研究显示利用数字摄影和图像分析技术对包括臼齿齿冠和齿尖面积在内的非线性特征进行精确的定量分析较传统的测量方法具有明显的优越性, 在古人类学和体质人类学研究中有广泛的应用前景。     

Brief communication: Possible third molar impactions in the hominid fossil record

Impacted third molars affect 15%–20% of modern Americans and Western Europeans. In contrast, third molar impactions have not been reported in the early hominid fossil record. It is uncertain whether the lack of reports reflects an absence of impactions or a failure to recognize them. This communication is intended to raise awareness of the possibility of impactions by describing the appearance of impacted teeth and by noting two possible instances of impaction in early hominids. Specifically, the mandibular third molars of the Sterkfontein specimen, STS52b (Australopithecus africanus), and the left maxillary third molar of the Lake Turkana specimen, KNM-WT17400 (Australopithecus boisei), are positioned in a manner which suggests that they would not have erupted normally. Both specimens also exhibit strong crowding of the anterior dentition, providing further support for the view that these individuals lacked sufficient space for normal eruption of the third molars. Other published reports of dental crowding in the hominid fossil record are noted, and it is suggested that more attention be paid to dental impaction and dental crowding in hominid evolution. © 1993 Wiley-Liss, Inc.     

Third molar agenesis in human prehistoric populations of the Canary Islands

The occurrence of third molar agenesis was recorded in a sample of 1,492 maxillary and 1,718 mandibular arches belonging to the prehistoric settlers of the Gan Canaria, Tenerife, and La Gomera Islands (Canary Islands). There were significant sex differences only in the Tenerife sample for the maxilla, the incidence in females being higher than in males. In the Gran Canaria sample, the total frequency (male and female combined) of third molar agenesis (individual count method) was 8.7% for the maxilla and 9.3% for the mandible. In the Tenerife and La Gomera samples, the frequencies were 11.1% and 10.7% for the maxilla and 14.6% and 13.3% for the mandible. In the Tenerife sample, the differences between both jaws were statistically significant. The incidence of missing third molars in the mandible was significantly higher in Tenerife than in Gran Canaria, but the other sample differences were statistically nonsignificant. Bilateral absence of third molars was observed in about two-thirds of the specimens examined. Some correlation between both jaws for the occurrence of third molar agenesis was found. The hypotheses that have been proposed in order to explain third molar agenesis in man are discussed. It is suggested that the loss of the third molar in Homo sapiens could be produced by a heterochronic phenomenon of postdisplacement, as a consequence of the phylogenetic tendency toward the delay of the onset of the third molar formation, and that the genetic factors responsible for the absence of these teeth could be related to the general process of delay in tooth formation.     

Influence of premolar extraction or non-extraction orthodontic therapy on the angular changes of mandibular third molars

AimTo compare the angular changes of the third molars relative to the occlusal plane and to the second molar long axis in extraction group and compare these changes with a non extraction group.Materials and methodsThe study included pre and post treatment panoramic radiograph records of 90 subjects treated by first premolar extractions and 90 subjects who had been treated with non extraction orthodontic therapy (n = 90). Two angular variables were measured. Firstly, the angle between the long axis of the third molar and the occlusal plane (M3–OP) and secondly, the angle between the long axis of the third molar and the long axis of the second molar (M3–M2). Data were analyzed by paired and student’s t-test.ResultThe analyzed data to assess the changes in the third molar angulation from pretreatment to post treatment did not vary significantly in both the groups (p < 0.05). Both the groups showed decreased angular values. The M3–OP angular difference was (−7.3 ± 2.45) in extraction group as compared to (−5.85 ± 1.77) in non extraction group. The M3–M2 angular difference of (−4.26 ± 3.11) in extraction group and (−2.98 ± 1.74) in non-extraction group was observed.ConclusionExtraction of premolars did not demonstrate considerable changes on the angulation of the third molars. The factors other than premolar extractions may influence the angulation of the third molars.     

Dental reductions and dental caries

Although first permanent molar hypoconulid absence, third molar agenesis, and small tooth size are all part of the evolutionary trend of dental reduction, each bears a different relationship to dental caries. Caries prevalence in the maxillary and mandibular permanent first molars of the Burlington Research Centre serial experimental group at age 16 years was less in the children whose first molars were missing the hypoconulid. Conversely, caries prevalence in mandibular first molars was greater in the children who had agenesis of third molars. The extraction of first molars due to caries was more frequent in children with agenesis of third molars, less frequent in those with absence of hypoconulids of the first molars and unrelated to tooth size. Caries prevalence was less in small teeth, and occurred least in the small mandibular first molars with four cusps. Whereas this is in harmony with the hypothesis that evolutionary dental reductions resulted from the pressure of caries, the increased prevalence of caries and extractions coinciding with third molar agenesis does not support this view. In addition, agenesis of hypoconulids and agenesis of third molars were related to changes in structures unrelated to caries.     

Association of relatively delayed emergence of mandibular molars with molar reduction and molar position

Among 234 children examined annually from age three to 20 years at the Burlington Growth Centre, there was statistically significant cooccurrence of early and late emergence sequences of the permanent first and second molars relative to the central incisors and second premolars in the same jaw and in both jaws. Alternatively, mandibular molar delay was not accompanied by corresponding maxillary molar delay, and the mandibular molars emerged later than the maxillary molars. This was strongly associated with Angle Class II malocclusion, indicating a relationship between relative time of emergence and relative position of opposing molars. Delay of the mandibular molar relative to the successional teeth or maxillary molars was associated with increased frequency of four cusped first and second molars and agenesis of third molars, indicating a tendency for co-occurrence of delay in timing of molar emergence with reduction in structure of the molars. These relationships were evident even though emergences were affected by early loss of a deciduous second molar which increased M1I1 and M2P2 sequences by earlier emergence of M1 and delayed emergence of P2.     

中国古人类进化连续性新辩

本文通过对一些形态特征的分析说明研究人类起源和进化应该注意的一些思维方法的问题,并且为多地区进化说增添了新的证据:1)中国更新世头骨共同具有的眼眶及其外侧下缘形状等特征在近代头骨中已有所改变,在考虑其意义时不应该忽略时间和基因交流起过的作用;2)中国更新世头骨的共同特征并不因为它们也可见于其他地区而丧失其意义,因为证明连续性的共同特征不需要是地区独有的;3)铲形门齿的结构在近代人中变弱,不削弱它作为连续进化证据的价值,这种弱化的现象是人类进化过程中形态纤巧化的一种表现;4)在辩论时不要对有关形态作不正确的观察和曲解对方的观点和论据;5)头骨正中矢状突隆、下颌圆枕、夹紧状鼻梁和第三臼齿先天性缺失等四项特征在近代非洲人中阙如,却存在于东亚近代人,本文的分析认为这种现象增强多地区进化说的说服力。     

Evolutionary dental changes.

In the evolution of primates there has been a tendency towards reduction in jaw length and prognathism, mandibular canine size and first molar cusp number, and third molar presence. These oral structures were contrasted, and compared with cranial size, body height and weight, and finger length in 118 males and 102 females of the Burlington Growth Centre. Body weight was significantly related to canine width and to jaw length and prognathism. These relationships were stronger in the males than in the females. The evolutionary reduction in these dental dimensions may result from an evolutionary reduction in genetically determined body size. In the males the number of molar cusps was related to finger length and cranial height. Agenesis of third molars was related to the length of the maxilla in both sexes. In the females, canine width was related to the number of cusps of the first molars, agenesis of third molars, and length of a finger. Simultaneous reductions in dental structures were more frequent in the females.     

Morphologic characteristics of the Alaskan Eskimo dentition: IV. Cusp number and groove patterns of mandibular molars

Data on the permanent dentition of 63 coastal and 33 inland Alaskan Eskimos are presented. The number of cusps and groove pattern of the mandibular molars were recorded. Agenesis of the mandibular third molars was classified and the mesiodistal and buccolingual crown diameter was measured on the first and the second mandibular molars. The predominant pattern of the lower first molars was Y5, while for the second molar the dominating patterns were +5 and +4. In the lower third molar, +5 was found in the majority of cases. For M1 and M2, men showed a stronger tendency toward a conservative pattern than did women. In the case of M2, the inland population exhibited a more conservative trait than did the coastal population. No connection was seen between the groove pattern and agenesis of M3, however, a reduction in the mesiodistal crown diameter for the second molars was seen when the number of cusps is reduced from 5 to 4.     

Tooth morphology and other aspects of the Teso dentition

The teeth of over 5,000 Teso schoolchildren members of a Nilo-Hamitic tribe in East Africa, were examined for morphological traits. There was a significant difference between the sexes in the number of cusps on the lower first and second molars, in the prevalence of the cusp of Carabelli, and in variability and agenesis of the upper lateral incisor. The results showed that females consistently favoured tooth reduction. There was also a tendency among those possessing extra cusps on one molar to have extra cusps or other molars. Records kept of the prevalence of the tribal custom of extracting lower central incisors indicated that this practise is rapidly dying out. On another group of teeth which had been extracted from adults common variations of root morphology were noted, together with the fissure pattern of the lower molars. Measurements were made of those teeth which were unworn and were not broken down by dental decay, and the lower third molar was found to be the largest tooth of the series. Observations on the pattern of molar tooth wear showed that the buccal as well as the occlusal surface was strongly affected.     

Comparaison de l'expression de certains caractères crâniens sur les hominidés chinois du Pléistocène récent et de l'Holocène (grotte supérieure de Zhoukoudian, sites de Longxian et de Yanqing)

The human remains recovered from “Grotte supérieure de Zhoukoudian” are the best-preserved Late Pleistocene human fossils in East Asia. For decades, as the representative of the Late Pleistocene human in East Asia, the Upper Cave skulls have been playing important role in the research of origins of modern Mongoloids and American Indians. With the advance of the origin and evolution of modern humans, more attention has been paid to the details and the mechanisms for the late Pleistocene human evolution and the formation of modern human populations. Both the origin and diversification of modern humans have been stressed. Some studies further trigger the debaters on the Upper Cave Man concerning its evolutionary level and its role in the formation of modern human populations in East Asia. To further explore these problems, we examined and compared 12 non-metric features on the 3 Late Pleistocene Upper Cave skulls and 162 Holocene individuals earthed from two archaeological sites of North China (Longxian and Yanqing). Our results indicate that 8 on the 12 features have different expression patterns between Upper Cave Man and recent Chinese leading the authors to believe that more primitive expressions appeared on the Upper Cave Man than on recent Chinese populations. Based on these findings, some problems on the intragroup variation in Late Pleistocene and Holocene populations are discussed.