Permanent Tooth Mineralization in Bonobos (Pan paniscus) and Chimpanzees (P. troglodytes) Julia C. Boughner, 1 * M. Christopher Dean, 2 and Chelsea S. Wilgenbusch 3 1 Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK, Canada 2 Department of Cell & Developmental Biology, University College London, London, UK 3 Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK, Canada KEY WORDS dental development; African great ape; radiographs; multivariate statistical analyses ABSTRACT The timing of tooth mineralization in bonobos (Pan paniscus) is virtually uncharacterized. Anal- ysis of these developmental features in bonobos and the possible differences with its sister species, the chimpanzee (P. troglodytes), is important to properly quantify the nor- mal ranges of dental growth variation in closely related pri- mate species. Understanding this variation among bonobo, chimpanzee and modern human dental development is nec- essary to better contextualize the life histories of extinct hominins. This study tests whether bonobos and chimpan- zees 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 den- tal scores failed to statistically distinguish between bono- bos 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 tim- ing of permanent tooth crown and root formation between bonobos and chimpanzees. Am J Phys Anthropol 149:560– 571, 2012. V V C 2012 Wiley Periodicals, Inc. Although life history does not fossilize, it may be reconstructed by comparing the dental development of extinct hominins with that of their closest living rela- tives. Thus far, modern humans and chimpanzees have been the two other modern comparative species. To accu- rately infer life history from fossil dental remains requires an understanding of the normal range of varia- tion in human and African ape dental developmental sequences and timings. Despite that chimpanzees (Pan troglodytes) and bonobos (P. paniscus) are sister species and both are the closest living cousins of modern humans, bonobo tooth mineralization is virtually unde- scribed. This study aims to help fill this significant gap in what is known about dental development in Pan by testing if covariance patterns among crown and root for- mation scores distinguish bonobos from chimpanzees. In general, published works that characterize and compare bonobo craniodental morphology and develop- ment against those of the chimpanzee are rare. These studies focus on varying degrees of interspecific differen- ces in ontogenetic growth pattern and form between P. paniscus and P. troglodytes (e.g., Fenart and Deblock, 1973; Shea, 1983a, 1983b; Kinzey, 1984; Shea and Coo- lidge Jr, 1988; Godefroit, 1990; McCollum and McGrew, 2001; Williams et al., 2003; Mitteroecker et al., 2005; Lieberman et al., 2007; Ponce de Leon and Zollikofer, 2007; Boughner and Dean, 2008; Singleton et al., 2011; Durrleman et al., 2012; Robinson, 2012). Only a limited number of studies has reported on bonobo tooth emer- gence and eruption, and even less so about tooth miner- alization. Timing and sequence of the emergence of the permanent canines, third molars, and upper lateral inci- sors appears to distinguish bonobos from chimpanzees (Bolter and Zihlman, 2011). In terms of deciduous tooth emergence, Smith et al. (1994) suggested that bonobo dental development was advanced by about 8 months compared to the chimpanzee. A recent histological analy- sis of bonobo M 1 and I 1 crown formation times (Ramirez- Rozzi and Lacruz, 2007) found that both teeth formed in a slightly shorter time compared to chimpanzees. These results are supported by a recent comparison of skeletal and dental emergence that found accelerated growth in P. paniscus relative to P. troglodytes (Bolter and Zihlman, 2012). Existing methods for accurately and precisely aging wild individual apes remain imperfect. Further, tooth emergence in free-living chimpanzees appears to happen later than in apes raised in captivity (Zihlman et al., 2004; Zihlman et al., 2007; Kelley and Schwartz, 2010). Additional Supporting Information may be found in the online version of this article. Grant sponsors: Natural Sciences and Engineering Research Council of Canada, The Colleges of Medicine and Dentistry (Univer- sity of Saskatchewan), The Leverhulme Trust, The Graduate School University College, London. *Correspondence to: Julia C. Boughner, Department of Anatomy and Cell Biology, University of Saskatchewan, Health Sciences Building, B328—107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada. E-mail: Julia.Boughner@gmail.com Received 17 May 2012; accepted 10 September 2012 DOI 10.1002/ajpa.22166 Published online 25 October 2012 in Wiley Online Library (wileyonlinelibrary.com). V V C 2012 WILEY PERIODICALS, INC. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 149:560–571 (2012)