The accuracy of histological assessments of dental development and age at death

Abstract

Histological analyses of dental development have been conducted for several decades despite few studies assessing the accuracy of such methods. Using known-period incremental features, the crown formation time and age at death of five pig-tailed macaques ( Macaca nemestrina ) were estimated with standard histological techniques and compared with known ages. Estimates of age at death ranged from 8.6% underestimations to 15.0% overestimations, with an average 3.5% overestimate and a 7.2% average absolute difference. Several sources of error were identified relating to preparation quality and section obliquity. These results demonstrate that histological analyses of dental development involving counts and measurements of short-and long-period incremental features may yield accurate estimates, particularly in well-prepared material. Values from oblique sections (or most naturally fractured teeth) should be regarded with caution, as obliquity leads to inflated cuspal enamel formation time and underestimated imbricational formation time. Additionally, Shellis's formula for extension rate and crown formation time estimation was tested, which significantly overestimated crown formation time due to underestimated extension rate. It is suggested that Shellis' method should not be applied to teeth with short, rapid periods of development, and further study is necessary to validate this application in other material.

Molar development in common chimpanzees (Pan troglodytes)

“…Smith et al (2004) reported crown extension rates for a single M 3 mesiobuccal cusp (protoconid) of Graecopithecus freybergi, which is similar to the values reported here for chimpanzees. In contrast, cusp-specific extension rates for macaques (Macaca nemestrina) are two to four times higher than hominoid values (Smith, 2004;Smith et al, 2006). It appears that, among extant and fossil great apes and humans, extension begins at a rather high rate in the crown, which progressively slows towards the cervix (Dean, 1998a;Smith et al, 2004), and then speeds up after the first or second millimeter of root formation.…”

“…To register cusps (or teeth) forming at the same time, accentuated lines in the enamel or dentine are usually identified and matched between cusps (or teeth). Alternatively, cessation of formation at death in developing teeth also allows cusps to be registered with one another (e.g., Dirks, 1998;Reid et al, 1998a;Smith et al, 2006).…”

“…Additionally, the degree of prism decussation was approximated, a corrected estimate of cuspal formation was determined, the uncorrected and corrected estimates were averaged, and the cuspal and imbricational regions were combined to yield total crown formation time. Smith et al (2006) applied a similar approach to estimate crown formation in several macaque molar cusps, and because it yielded fairly accurate estimates, it was assumed to be appropriate for these lightly worn cusps.…”

Dental evidence for ontogenetic differences between modern humans and Neanderthals

“…Moreover, the remarkable production of a line coincident with birth in permanent first molars (M1s) allows developmental time to be registered with an individual's actual age. When this neonatal line can be identified and subsequent development assessed from enamel and dentine increments, age at death may be estimated to within 5% of an individual's true age (21)(22)(23). This histological approach is a substantial improvement over the nearly ubiquitous application of recent human or ape developmental standards to age juvenile hominins.…”

Rapid dental development in a Middle Paleolithic Belgian Neanderthal

“…12,22,23). Resolution of the debate regarding whether Neanderthals and modern humans follow disparate ontogenetic trajectories has been slowed by a lack of data from histological sections of teeth (2).…”