Dental development in chimpanzees ( Pan troglodytes ): The timing of tooth calcification stages

Abstract

Data are presented documenting the timing of tooth calcification for the left mandibular dentition (I1-M3) based on a cross-sectional series of intraoral dental X-rays from a sample of 118 captive chimpanzees. Mean, median, and midpoint ages of attainment; standard deviations (SD); interquartile ranges (IQR); and age ranges were calculated for the eight developmental stages of these teeth. Minor differences with previous studies of chimpanzee dental development were found (Anemone et al. [1991] Am. J. Phys. Anthropol. 86:229-241; Anemone and Watts [1992] J. Hum. Evol. 22:149-153), but the similarities with previous studies are more striking despite the differences in samples. In contrast to other pongid studies, sex differences in developmental timing were documented, particularly for the canine. Regression models for age estimation from dental maturity scores were also presented. This chimpanzee standard is compared with human standards to determine absolute and relative differences in the timing of crown and root calcification. The overall period of canine development in both species is nearly identical, although those for crown and root formation are markedly different--making this tooth the most distinctive feature between chimpanzee and human dental development periods. Although the molars demonstrate differences in the timing of crown and root calcification periods, they are more proportional than for other teeth. This contributes to the difficulties in distinguishing between "human" and "chimpanzee" patterns of molar development. The developmental differences discussed are placed in perspective with consideration to microstructural and morphological features of chimpanzee and human teeth, and to overall growth periods in these species.

A geometric morphometric analysis of heterochrony in the cranium of chimpanzees and bonobos

“…First, although the sequence of tooth eruption is notoriously variable within species, the general eruption sequences in bonobos and chimpanzees are essentially identical for both the permanent and deciduous dentitions (Boughner and Dean, 2004), with delay of the I2 being the most common difference (Kinzey, 1984). Second, estimates of the age of Kuykendall (1996) and Dean and Wood (1981) (see text for details). eruption of deciduous teeth from a small sample of bonobos (n ¼ 4) fall within the chimpanzee range, although at the low end (Smith et al, 1994).…”

“…A third problem is that the only aging data available for the genus Pan come from cross-sectional studies (Dean and Wood, 1981;Kuykendall, 1996;Anemone et al, 1996), which yield more error than longitudinal studies. Longitudinal data from both species would be better (but present their own problems in terms of aligning individual trajectories), but as shown by German (2004), cross-sectional data are still useful despite their lower resolution when there is general similarity in terms of the slope of the relationship between ontogenetic events and time.…”

“…Accordingly, ontogenetic stage was estimated for both species using two studies: one by Dean and Wood (1981) and the other by Kuykendall (1996). First, CT images of each mandible were used to estimate age using tooth-developmental stages from Dean and Wood's (1981) study.…”

“…As a second step, estimates based on Dean and Wood's (1981) stages were then checked against age estimates derived using the tooth-formation stages for I 1 , M 1 , M 2 , and M 3 from Kuykendall's (1996) study. In all cases, the dental-age estimate derived using Dean and Wood's (1981) stages fell within the range derived from Kuykendall's (1996) stages. Note that the ontogenetic-age estimates used here are not estimates of absolute chronological age for either species.…”

Molar development in common chimpanzees (Pan troglodytes)

“…Assessments of the skeletal and dental development of chimpanzees have been underway since before the beginning of the twentieth century (Keith, 1899;Selenka, 1899), continuing today in both captive and natural environments (e.g., Kraemer et al, 1982;Goodall, 1986;Anemone et al, 1991Anemone et al, , 1996Kuykendall, 1996;Marzke et al, 1996;Zihlman et al, 2004). Hominoid dental development and tooth emergence have historically been valued because they offer insight into theories of life history and phylogeny (Zuckerman, 1928;Krogman, 1930;Schultz, 1935;Bennejeant, 1940;Clements and Zuckerman, 1953;Gavan and Swindler, 1966;Gavan, 1967), as well as the absolute ages of individuals that are still developing their dentitions (e.g., Garn et al, 1959;Bailit, 1976;Dean and Wood, 1981;Smith et al, 1994).…”