A Faithful Record of Stressful Life Events Recorded in the Dental Developmental Record of a Juvenile Gorilla

Abstract

The pattern and rate of dental development are critical components of the life history of primates. Much recent research has focused on dental development in chimpanzees and other hominoids, but comparatively little is known about dental development in Gorilla. To date, dental chronologies for Gorilla are based on a sample of 1 and information about variations in the time and timing of crown initiation and completion is lacking. We provide data on dental development in 1 captive, juvenile, female, western lowland Gorilla gorilla gorilla of known age, sex, life events, and date of death (carefully documented as part of zoo records) that experienced various physical insults during her first year of life. The perfect natural experiment allowed us to test the association of the timing of accentuated stress lines in teeth with significant physiological and psychological events during ontogeny of this juvenile gorilla. We analyzed histological sections from 14 permanent teeth (maxillary and mandibular I1-M2) and assessed crown initiation (CI) and crown formation times (CFT) using short-and long-period incremental lines in both enamel and dentine; they are advanced for all teeth compared to previously published chronology. The data suggest a relatively accelerated pace of dental development in gorillas compared to chimpanzees and fit an emerging pattern of an accelerated life history schedule in gorillas. Data on the timing of major accentuated lines in the developing dentition are tightly associated with exact dates of surgical procedures and follow-up hospital visits as recorded on zoo medical records. Our data highlight the importance of captive individuals with well-documented medical records for studying life history.

The secrets of lemur teeth

“…The etiology of accentuated lines is even less clear; however, we do know that these lines chart the temporal position of stressful episodes. 33 Any single "stressful" event, which may be nutritional, physiological, or even psychological, 34 will affect the cells of all developing teeth and will therefore mark the same moment in time.…”

Quantifying linear enamel hypoplasia in Virunga Mountain gorillas and other great apes

“…Social interaction and disturbance, as revealed by endocrine data from other species, are other potential sources of stress (Bahr, Pryce, Döbeli, & Martin, ; Muller & Wrangham, ). Human disturbance and changes in social dynamics have been found to correspond with accentuated lines in primate dentitions (Dirks, Humphrey, Dean, & Jeffries, ; Dirks, Reid, Jolly, Phillips‐Conroy, & Brett, ; McFarlin et al, ; Schwartz, Reid, Dean, & Zihlman, ). Schwartz et al () additionally found accentuated lines to correspond with injuries and hospital visits in a captive western lowland gorilla.…”

Updating histological data on crown initiation and crown completion ages in southern Africans

“…With the data now available for initiation times in early and later fossil hominins (Smith et al, ,b, 2010, 2015) and other published data on extant great apes (Beynon, Dean, & Reid, ; Reid, Schwartz, Dean, & Chandrasekera, ; Schwartz, Reid, Dean, & Zihlman, ; Smith, Reid, Dean, Olejniczak, & Martin, ) it becomes increasingly likely that early hominins more closely resembled modern humans in their range of initiation times than living great apes, perhaps suggesting a grade shift in initiation times, at least for posterior teeth, early in human evolution. In any case, given that the data for crown initiation and crown completion for the M2s and M3s of this southern African sample are considerably earlier than those of European samples (Reid and Dean, ), data from this study narrow the differences between modern humans and other hominins in initiation and crown completion ages for these tooth types.…”