Developmental defects in the teeth of three wild chimpanzees from the Taï forest

Developmental defects in teeth (accentuated lines and hypoplasias) have played a critical role in studies of childhood disease, nutrition, weaning, environmental variation, and early mortality. While these enigmatic structures have been lauded for their potential insights into human evolution, few studies have examined defects in individuals of known histories.

Here we document defects in the molars of three wild juvenile chimpanzees from the Taï forest (Pan troglodytes verus) and compare them with behavioral, epidemiological, and environmental records.

Accentuated lines of differing intensities were found throughout molar crown and root growth, and were most common in a juvenile who demonstrated slow skeletal growth and prolonged maternal dependence. These defects were observed in association with some but not all injuries and disease outbreaks in this community. A 10-year record of accentuated line frequency across individuals shows a significant negative correlation with rainfall, but does not correlate with fruit availability or reveal significant annual trends. Several hypoplasias formed between ∼0.6 and 5.8 years of age on molar crowns and roots of the three individuals, however, available behavioral and epidemiological records do not explain their causation.

While teeth may provide precise and accurate records of illness and trauma in some cases, inferring seasonal cycles, social stress, or weaning in living or fossil primate dentitions requires additional evidence beyond the presence, absence, or degree of expression of these defects. Studies that microsample bulk and trace elements may provide a more secure context for the interpretation of environmental, physiological, and dietary changes that impact dental tissue formation.