The Relationship of Accentuated Lines in Enamel to Weaning Stress in Juvenile Baboons (Papio hamadryas anubis)

Abstract

Weaning conflict may represent an evolutionary conflict of interest between parent and offspring, an honest signal of need on the part of a weanling, or both. Accentuated lines visible in histological sections of teeth are indicators of stress during enamel formation and have been hypothesised to form in baboon teeth during weaning. We analysed growth increments in 5 tooth sections from 2 Ugandan baboons (Papio hamadryas anubis), using polarised light microscopy, to determine when stresses occurred during the weaning process. Dietary transitions were reconstructed using normalised strontium intensities (Sr/Ca) in enamel. Accentuated lines were cross-matched between teeth from the same animal and plotted by month. The highest frequency of stress was experienced at around 6 months in 1 baboon, coinciding with an inferred reduction in suckling frequency, and at 11 months in another, coinciding with the inferred cessation of suckling. Because accentuated lines appear to indicate weaning stress at dietary transitions, weaning conflict may represent an honest signal of need on the part of the weanling.

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

“…Our study underscores the challenge of relating defects to particular events in the histories of wild juvenile primates (Dirks et al, 2002(Dirks et al, , 2010. Our study underscores the challenge of relating defects to particular events in the histories of wild juvenile primates (Dirks et al, 2002(Dirks et al, , 2010.…”

“…Dirks et al (2010) conducted an innovative study of accentuated lines and trace elements in two wild male baboons of unknown developmental histories. The three individuals in our study did not show markedly greater frequencies of accentuated lines from 2 to 4 years of age than during preceding years.…”

“…B) Cast of the same tooth illustrating the approximate plane of section (yellow dotted line), the presence of two marked hypoplasias corresponding to accentuated lines at 3.1 and 3.5 years (pink and blue arrows, respectively), and several root hypoplasias formed after 4.5 years of age (black arrows). Studies of nonhuman primates have emphasized potential relationships between accentuated lines and rainfall patterns, changes in nutrition, social disruptions, poor physical growth, disease, physical trauma, weaning, and maternal life history events (Bowman, 1991;Macho et al, 1996;Dirks, 1998;Dirks et al, 2002;Schwartz et al, 2006;Dirks et al, 2010;Smith, 2013;Austin et al, in review). com.…”

“…] postnatal immunizations (Birch and Dean, 2014), and parturition in females who are still growing their third molars (Dean and Elamin, 2014). Dirks et al (2010) combined studies of accentuated lines with trace element analysis of two baboons from Uganda, and hypothesized that accentuated lines at certain ages indicated physiological stress due to a reduction or cessation of suckling. Macho et al (1996) examined accentuated lines in 11 molars of the fossil monkey Theropithecus oswaldi, and suggested that annual seasonal signals were apparent in the timing of accentuated lines, as well as shorter intervals that may reflect the onset of the rainy season and the peak of the dry season.…”

The tooth exposome in children's health research

“…Other accentuated growth lines have been observed, largely in enamel, which are similarly believed to be due to the disruption of tooth matrix deposition due to external stressors, both physical and social [82–84]. Several studies have compared the timing of these accentuated lines with clinical events such as injuries, bouts of dehydration/diarrhea, and hospitalizations [85–87] and other events such as weaning [88, 89], and separation from dam [90]. These accentuated lines are typically identified and aged using light microscopy.…”