Mortality and the magnitude of the "wild effect" in chimpanzee tooth emergence

Age of tooth emergence is a useful measure of the pace of life for primate species, both living and extinct. A recent study combining wild chimpanzees of the Taï Forest, Gombe, and Bossou by Zihlman et al. (2004) suggested that wild chimpanzees erupt teeth much later than captives, bringing into question both comparisons within the hominin fossil record and assessment of chimpanzees. Here, we assess the magnitude of the “wild effect” (the mean difference between captive and wild samples expressed in standard deviation units) in these chimpanzees. Tooth emergence in these wild individuals is late, although at a more moderate level than previously recorded, with a mean delay conservatively estimated at about 1 SD compared to the captive distributions. The effect rises to 1.3 SD if we relax criteria for age estimates. We estimate that the mandibular M1 of these wild chimpanzees emerges at about 3 ²/₃-3 ¾ years of age. An important point, often ignored, is that these chimpanzees are largely dead of natural causes, merging the effect of living wild with the effect of early death. Evidence of mortality selection includes, specifically: younger deaths appear to have been more delayed than the older in tooth emergence, more often showed evidence of disease or debilitation, and revealed a higher occurrence of dental anomalies. Notably, delay in tooth emergence for live-captured wild baboons appears lower in magnitude (ca. 0.5 SD) and differs in pattern. Definitive ages of tooth emergence times in living wild chimpanzees must be established from the study of living animals. The fossil record, of course, consists of many dead juveniles; the present study has implications for how we evaluate them.     

Skeletal and dental growth and development in chimpanzees of the Taï National Park, Côte D'Ivoire

An extraordinary collection of 22 immature skeletons from Taï National Park, Côte d'Ivoire, has provided a rare opportunity to establish the timing of dental eruption and its correlation with skeletal fusion and morphometrics in wild chimpanzees of known chronological ages. Comparison of the immature Taï chimpanzees Pan troglodytes verus with adults from the same population show that sex differences in skeletal maturation apparently appear during the Juvenile II stage, about age 8. A few skeletons from other chimpanzee field sites conform to the dental and skeletal growth in Taï chimpanzees. The tempo of wild chimpanzee growth contrasts sharply with the rate demonstrated for captive individuals. Captive chimpanzees may mature as much as 3 years earlier. The ability to link physical development with field observations of immature chimpanzees increases our understanding of their life-history stages. These data provide an improved dataset for comparing the rates of growth among chimpanzees, Homo sapiens and fossil hominids.     

Variation in crown and root formation and eruption of human deciduous teeth

The aim of this study was to document variation of deciduous tooth formation and eruption. The material comprises 121 individuals of known or estimated age (using tooth length) from Spitalfields in London, and radiographs of 61 healthy living children aged 2-5 years. Other skeletal material from two medieval Scottish archaeological sites (Whithorn, N=74; Newark Bay, N=59) was also examined. Stages of crown and root formation as well as eruption (alveolar, midway, and occlusal levels) were assessed for each developing maxillary and mandibular tooth from radiographs or direct vision. Age of attainment for individual stages was calculated by probit analysis, and these data were also adapted for use in estimating age. The timing of crown completion was similar to previously reported studies, but apex completion times were later. Analysis of data relative to the first and second molars at the two stages D (crown complete) and F (root length > or =crown height) allowed comparison with the Scottish material. No significant differences were observed between population groups for tooth formation or eruption. These data fill several gaps in the literature, and will be useful in assessing maturity and predicting age during early childhood.     

Skeletal development in Pan paniscus with comparisons to Pan troglodytes

Fusion of skeletal elements provides markers for timing of growth and is one component of a chimpanzee's physical development. Epiphyseal closure defines bone growth and signals a mature skeleton. Most of what we know about timing of development in chimpanzees derives from dental studies on Pan troglodytes. Much less is known about the sister species, Pan paniscus, with few in captivity and a wild range restricted to central Africa. Here, we report on the timing of skeletal fusion for female captive P. paniscus (n = 5) whose known ages range from 0.83 to age 11.68 years. Observations on the skeletons were made after the individuals were dissected and bones cleaned. Comparisons with 10 female captive P. troglodytes confirm a generally uniform pattern in the sequence of skeletal fusion in the two captive species. We also compared the P. paniscus to a sample of three unknown‐aged female wild P. paniscus, and 10 female wild P. troglodytes of known age from the Taï National Park, Côte d'Ivoire. The sequence of teeth emergence to bone fusion is generally consistent between the two species, with slight variations in late juvenile and subadult stages. The direct‐age comparisons show that skeletal growth in captive P. paniscus is accelerated compared with both captive and wild P. troglodytes populations. The skeletal data combined with dental stages have implications for estimating the life stage of immature skeletal materials of wild P. paniscus and for more broadly comparing the skeletal growth rates among captive and wild chimpanzees (Pan), Homo sapiens, and fossil hominins. Am J Phys Anthropol 2012. © 2012 Wiley Periodicals, Inc.     

Growth of wild and laboratory born chimpanzees

The skeletal remains of a wild juvenile chimpanzee,Pan troglodytes verus, of known chronological age are measured and found to be smaller than laboratory born and fed juveniles of the same age. Other wild born immature skeletal materials of all the three subspecies ofPan troglodytes, including both known and estimated chronological ages, are also smaller than laboratory born chimpanzees when comparisons are made on corresponding age groups. Differences between wild and laboratory born chimpanzees are larger in the limb bones than in the cranium. Limb bones of laboratory individuals grow earlier than those of wild ones regardless of subspecies. Small limb bone size of wild chimpanzees is discussed in terms of life processes.     

Human tooth development,tooth length and eruption; a study of British archaeological dentitions

Abstract

Human teeth erupt during root growth but few studies report the relationship between fractions of root development and eruption levels. The aim of this study was to assess root stages of deciduous and early erupting permanent teeth (maxillary and mandibular central incisors and first molars) at eruption levels and relate this to root fraction and tooth length. The sample consisted of 620 modern human skeletal remains with developing teeth. Tooth stage (based on Moorrees crown and root stages) and eruption levels of all developing teeth were assessed where possible. Tooth length of isolated teeth was measured. The distribution of root stage at eruption levels was calculated. Results showed that root stage at alveolar eruption was less variable than at partial eruption. Most teeth (72% of 138) at alveolar eruption were at root a quarter (R¼) whereas teeth at partial eruption were at R¼ or root half (R½) (38 and 50% of 128 respectively). These findings suggest that the active phase of eruption is probably a rapid process and occurs during the first half of root growth.     

Permanent tooth mineralization in bonobos (Pan paniscus) and chimpanzees (P. troglodytes)

The timing of tooth mineralization in bonobos (Pan paniscus) is virtually uncharacterized. Analysis of these developmental features in bonobos and the possible differences with its sister species, the chimpanzee (P. troglodytes), is important to properly quantify the normal ranges of dental growth variation in closely related primate species. Understanding this variation among bonobo, chimpanzee and modern human dental development is necessary to better contextualize the life histories of extinct hominins. This study tests whether bonobos and chimpanzees are distinguished from each other by covariance among the relative timing and sequences of tooth crown initiation, mineralization, root extension, and completion. Using multivariate statistical analyses, we compared the relative timing of permanent tooth crypt formation, crown mineralization, and root extension between 34 P. paniscus and 80 P. troglodytes mandibles radiographed in lateral and occlusal views. Covariance among our 12 assigned dental scores failed to statistically distinguish between bonobos and chimpanzees. Rather than clustering by species, individuals clustered by age group (infant, younger or older juvenile, and adult). Dental scores covaried similarly between the incisors, as well as between both premolars. Conversely, covariance among dental scores distinguished the canine and each of the three molars not only from each other, but also from the rest of the anterior teeth. Our study showed no significant differences in the relative timing of permanent tooth crown and root formation between bonobos and chimpanzees. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

Improvement of dental development in osteopetrotic mice by maternal vitamin D3 sulfate administration

Utilizing the microphthalamic mouse, (mi/mi) as a model of osteopetrosis, vitamin D3 (cholecalciferol) was administered prenatally and postnatally to study its effects on tooth development and subsequent eruption. It has previously been reported that vitamin D3 crosses the placental barrier and is absorbed into mammary gland milk. Fifteen heterozygotes (+/mi) were used as breeders. There were three study groups: A) 5.0 ng/gm cholecalciferol sulfate; B) 2.5 ng/gm cholecalciferol sulfate; and C) no therapy. Intraperitoneal injections were administered three times per week, beginning when pregnancy was evident, and continuing for 4 additional weeks during lactation. Approximately half of the 59 offspring were sacrificed at age 1 day and the other half at 4 weeks. The former group was studied for crown development, and the latter group was studied for root development and eruption. When the osteopetrotic offspring of group A were compared with osteopetrotic offspring of group C, crown development and tooth eruption were substantially more advanced. Parameters examined were maturity of the ameloblasts and odontoblasts, dentin and enamel formation, root sheath development, status of eruption, and degree of apex closure. It was concluded that cholecalciferol sulfate significantly improves tooth development and subsequent eruption in the osteopetrotic mouse. A genetic disease has had its phenotype modified by vitamin therapy during gestation.     

Dental eruption schedules of wild and captive baboons

Dental eruption schedules previously used to age wild baboons have in the past derived from studies of captive animals housed under standard conditions and fed standard laboratory diets. This paper reports for the first time eruption schedules derived from wild baboons, the yellow baboons (Papio hamadryas cynocephalus) of Mikumi National Park, Tanzania, and compares these schedules with those of other baboon subspecies inhabiting both similar and dissimilar environments. Eighteen males and twelve females from the Viramba groups, ranging in age from 21 to 103 months, were trapped, and dental impressions and notes were made of the state of eruption of each tooth. Eruption of all teeth were delayed at Mikumi relative to the baboon standards derived from the captive animals at the Southwest Foundation for Biomedical Research, San Antonio, Texas. Teeth of the canine-premolar 3 complex and third molars were most delayed, erupting up to a year and a half later than their counterparts from captive animals. Comparison with data on hamadryas baboons from Erer-Gota in Ethiopia revealed that both the hamadryas and yellow subspecies of baboons, with different genetic backgrounds and living under markedly different environmental conditions, followed the same schedule. This constancy of developmental schedules suggests that these Mikumi data may reasonably be used as standards for other wild baboon populations and that acceleration of dental maturation, as well us maturation of other somatic systems in captivity, is another manifestation of the short-term adaptive plasticity of the baboon species as a whole.     

Altruism in Forest Chimpanzees: The Case of Adoption

In recent years, extended altruism towards unrelated group members has been proposed to be a unique characteristic of human societies. Support for this proposal seemingly came from experimental studies on captive chimpanzees that showed that individuals were limited in the ways they shared or cooperated with others. This dichotomy between humans and chimpanzees was proposed to indicate an important difference between the two species, and one study concluded that “chimpanzees are indifferent to the welfare of unrelated group members”. In strong contrast with these captive studies, consistent observations of potentially altruistic behaviors in different populations of wild chimpanzees have been reported in such different domains as food sharing, regular use of coalitions, cooperative hunting and border patrolling. This begs the question of what socio-ecological factors favor the evolution of altruism. Here we report 18 cases of adoption, a highly costly behavior, of orphaned youngsters by group members in Taï forest chimpanzees. Half of the adoptions were done by males and remarkably only one of these proved to be the father. Such adoptions by adults can last for years and thus imply extensive care towards the orphans. These observations reveal that, under the appropriate socio-ecologic conditions, chimpanzees do care for the welfare of other unrelated group members and that altruism is more extensive in wild populations than was suggested by captive studies.     

Brief communication: on the optimum number of metacarpals for roentgenogrammetric measurement

Interpretation of dental development of fossil hominids requires understanding of and comparison with the pattern and timing of dental development among living humans and pongids. We report the first study of crown and root calcification in the lower permanent molar teeth among chimpanzees (Pan troglodytes) of known chronological age. A series of 99 lateral head radiographs of 16 captive-born chimpanzees were analyzed. Radiographs were taken at irregular intervals throughout the entire postnatal period of dental development from birth to 13 years of age. Permanent mandibular molars were rated on an eight-point maturation scale from initial radiographic appearance through crown and root calcification and apical closure of the root canals. In addition, we were able to document initial crown calcification and completion, as well as root completion and apical closure in incisors, canines, and premolars. Our results show several differences from the widely cited developmental schedule for pongid dentitions of Dean and Wood (Folia Primatol. 36:111–127, 1981). We found a much greater degree of temporal overlap in calcification of the crowns of adjacent molars, a pattern very unlike that usually seen in human dental development, which is characterized by delays between the onset of crown calcification in the molar series. Also, the ages and durations of crown and root formation in our chimp sample differ from the estimates proposed by Dean and Wood. By more clearly establishing the nature of developmental schedules and the timing of major events in the pongid dentition, these results should aid in the ongoing controversies concerning the human or pongid nature of dental development among Plio-Pleistocene hominids.     

Territory Characteristics among Three Neighboring Chimpanzee Communities in the Taï National Park,Côte d'Ivoire

We studied territory characteristics among three neighboring chimpanzee communities in the Taï National Park, Côte d'Ivoire, and compared them with other chimpanzee populations. We characterized territories and ranging patterns by analyzing six variables:, (1) territory size, (2) overlap zone, (3) territory utilization, (4) core area, (5) territory shift, and (6) travel distance. Data collection covered a period of 10 mo, during which we simultaneously sampled the local positions of mostly large parties, including males in each community, in 30-min intervals. In Taï, chimpanzees used territories in a clumped way, with small central core areas being used preferentially over large peripheral areas. Although overlap zones between study communities mainly represented infrequently visited peripheral areas, overlap zones with all neighboring communities also included intensively used central areas. Territory utilization was not strongly seasonal, with no major shift of activity center or shift of areas used over consecutive months. However, we observed shorter daily travel distances in times of low food availability. Territory sizes of Taï chimpanzees tended to be larger than territories in other chimpanzee communities, presumably because high food availability allows for economical defense of territorial borders and time investment in territorial activities. Therefore we suggest, that use of territory in Taï chimpanzees is strongly influenced by intercommunity relations. To understand differences in territory characteristics between various populations, it is of major importance to consider not only the intracommunity but also the intercommunity context.     

Molar development in common chimpanzees (Pan troglodytes)

Numerous studies have reported on enamel and dentine development in hominoid molars, although little is known about intraspecific incremental feature variation. Furthermore, a recent histological study suggested that there is little or no time between age at chimpanzee crown completion and age at molar eruption, which is unlikely given that root growth is necessary for tooth eruption. The study presented here redefines growth standards for chimpanzee molar teeth and examines variation in incremental features. The periodicity of Retzius lines in a relatively large sample was found to be 6 or 7 days. The number of Retzius lines and cuspal enamel thickness both vary within a cusp type, among cusps, and among molars, resulting in marked variation in formation time. Daily secretion rate is consistent within analogous cuspal zones (inner, middle, and outer enamel) within and among cusp types and among molar types. Significantly increasing trends are found from inner to outer cuspal enamel (3 to 5 microns/day). Cuspal initiation and completion sequences also vary, although sequences for mandibular molar cusps are more consistent. Cusp-specific formation time ranges from approximately 2 to 3 years, increasing from M1 to M2, and often decreasing from M2 to M3. These times are intermediate between radiographic studies and a previous histological study, although both formation time within cusps and overlap between molars vary considerably. Cusp-specific (coronal) extension rates range from approximately 4 to 9 microns/day, and root extension rates in the first 5 mm of roots range from 3 to 9 microns/day. These rates are greater in M1 than in M2 or M3, and they are greater in mandibular molars than in respective maxillary molars. This significant enlargement of comparative data on nonhuman primate incremental development demonstrates that developmental variation among cusp and molar types should be considered during interpretations and comparisons of small samples of fossil hominins and hominoids.     

乌干达野生动物研究中心外来黑猩猩融入笼养群体的过程

1967至1997的30年间,生活在非洲热带地区自然栖息地的野生黑猩猩数量由60万降至不足20万,至今这个数字仍在减少,因此引起了全球的关注并急需要开展迁地保护。笼养黑猩猩与野外种群一样营群居生活,为了有效进行野生黑猩猩的迁地保护,将野外捕获的野生黑猩猩个体成功引入已在动物园的黑猩猩群体中十分必要。2004年10月至2005年3月,乌干达野生动物研究中心首先开展了这一实验。同时为更好地了解外来黑猩猩融入笼养群体的过程,2006年9月至2007年1月间收集其活动数据。选取5只黑猩猩个体并记录它们的食性、行为、体重变化及身体健康状况。除直接观察和记录外,与兽医和研究中心管理人员进行合作,以获取较多笼养个体的信息。我们发现,野生个体比笼养个体多病,因此影响了它们的取食、社会行为及活动水平。尽管笼养黑猩猩有人照料,但仍具备野生个体的行为,所以,理解外来黑猩猩融入笼养群体的过程对于黑猩猩的迁地保护和就地保护是非常重要的。     

A comparison of buttress drumming by male chimpanzees from two populations

Wild chimpanzees (Pan troglodytes) produce low-frequency sounds by hitting the buttresses and/or trunks of trees. This buttress drumming occurs in discrete bouts that may be integrated into the phrase sequence of the chimpanzees long-distance vocalization, the pant hoot. The aim of this study was to investigate whether regional variation exists in the drumming behavior of male chimpanzees from Kibale National Park (Kanyawara community), Uganda, and Taï National Park, Ivory Coast. Recordings were made during a 6-month field season at Taï in 1990, and a 12-month field season at Kanyawara in 1996–1997. Acoustic analysis revealed the following: (1) Kanyawara males drummed significantly less frequently in conjunction with a pant hoot or hoot than did Taï males; (2) drumming bouts by Kanyawara males included significantly fewer beats, and were significantly shorter in duration, than those of Taï males; these differences disappeared when only those bouts produced in conjunction with a call were compared; (3) when Kanyawara chimpanzees did call and drum together, they tended to integrate drumming into the vocalization at a later point than did Taï males; and (4) individual differences in the temporal patterning of drumming bouts were not apparent for Kanyawara males, whereas a previous analysis revealed individual differences among Taï males.     

Probit and survival analysis of tooth emergence ages in a mixed-longitudinal sample of chimpanzees (Pan troglodytes).

Tooth emergence data from a mixed-longitudinal sample of 58 chimpanzees of known age were analyzed using probit and survival techniques to produce median emergence ages, ranges of variability, and emergence sequences for primary and permanent teeth. Between-group comparisons were made to test for statistically significant differences in emergence ages. No such differences were found between right and left sides, or between maxilla and mandible, for any primary or permanent teeth. Male-female comparisons did demonstrate significant emergence-age differences for some teeth, although they were not always bilaterally symmetrical. More complete data are required to further clarify the nature of sex differences in tooth emergence in chimpanzees. Regression models for age prediction from the number of emerged teeth were generated and indicate that males achieve a given number of emerged teeth at a significantly later age than females. However, when fewer than five teeth have emerged, males are predicted to be younger than females. The sizable root mean square error values for these models suggest that this method of age prediction has limited usefulness owing to the amount of variability in timing of tooth emergence in chimpanzees. The implications of these data for studies on tooth emergence in early hominids are addressed.     

Increasing human tooth length between birth and 5.4 years

Most previous studies of tooth development have used fractional stages of tooth formation to construct growth standards suitable for aging juvenile skeletal material. A simple alternative for determining dental age is to measure tooth length throughout development. In this study, data on tooth length development are presented from 63 individuals of known age at death, between birth and 5.4 years, from an archeological population recovered from the crypt of Christ Church, Spitalfields, London. Isolated developing teeth (304 deciduous, 269 permanent) were measured in millimeters and plotted against individual age. Regression equations to estimate age from a given tooth length, are presented for each deciduous maxillary and mandibular tooth type and for permanent maxillary and mandibular incisors, canines, and first permanent molars. Data on the earliest age of root completion of deciduous teeth and initial mineralization and crown completion of some permanent teeth in this sample are given, as well as the average crown height and total tooth length from a small number of unworn teeth. This method provides an easy, quantitative and objective measure of dental formation appropriate for use by archeologists and anthropologists. © 1993 Wiley-Liss, Inc.     

Incremental enamel development in modern human deciduous anterior teeth

This study reconstructs incremental enamel development for a sample of modern human deciduous mandibular (n = 42) and maxillary (n = 42) anterior (incisors and canines) teeth. Results are compared between anterior teeth, and with previous research for deciduous molars (Mahoney: Am J Phys Anthropol 144 (2011) 204-214) to identify developmental differences along the tooth row. Two hypotheses are tested: Retzius line periodicity will remain constant in teeth from the same jaw and range from 6 to 12 days among individuals, as in human permanent teeth; daily enamel secretion rates (DSRs) will not vary between deciduous teeth, as in some human permanent tooth types. A further aim is to search for links between deciduous incremental enamel development and the previously reported eruptionsequence. Retzius line periodicity in anterior teeth ranged between 5 and 6 days, but did not differ between an incisor and molar of one individual. Intradian line periodicity was 12 h. Mean cuspal DSRs varied slightly between equivalent regions along the tooth row. Mandibular incisors initiated enamel formation first, had the fastest mean DSRs, the greatest prenatal formation time, and based upon prior studies are the first deciduous tooth to erupt. Relatively rapid development in mandibular incisors in advance of early eruption may explain some of the variation in DSRs along the tooth row that cannot be explained by birth. Links between DSRs, enamel initiation times, and the deciduous eruption sequence are proposed. Anterior crown formation times presented here can contribute toward human infant age-at-death estimates. Regression equations for reconstructing formation time in worn incisors are given.     

Regulatory mechanisms of Hertwig׳s epithelial root sheath formation and anomaly correlated with root length

Teeth are composed of two domains, the enamel-covered crown and cementum-covered root. The mechanism for determining the transition from crown to root is important for understanding root anomaly diseases. Hertwig?s epithelial root sheath (HERS) is derived from the dental epithelium and is known to drive the growth of root dentin and periodontal tissue. Some clinical cases of hypoplastic tooth root are caused by the cessation of HERS development. Understanding the mechanisms of HERS development will contribute to the study of the disease and dental regenerative medicine. However, the developmental biology of tooth root formation has not been fully studied, particularly regarding HERS formation. Here, we describe the mechanisms of HERS formation on the basis of analysis of cell dynamics using imaging and summarize how the growth factor and its receptor regulate cell behavior of the dental epithelium.