Elemental models of primate nursing and weaning revisited

Smith, Tanya M.; Arora, Manish; Bharatiya, Maya; Dirks, Wendy; Austin, Christine

Abstract

Objectives
Intra-tooth patterns of trace elements barium (Ba) and strontium (Sr) have been used to infer human and nonhuman primate nursing histories, including australopithecine and Neanderthal juveniles. Here, we contrast the two elemental models in first molars (M1s) of four wild baboons and explore the assumptions that underlie each.

Materials and Methods
Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was employed to create comprehensive calcium-normalized barium and strontium (Ba/Ca, Sr/Ca) maps of M1 enamel and dentine at 35 micron resolution.

Results
Postnatal Ba/Ca values were typically high, peaking ~0.5 years of age and then decreasing throughout M1 crown formation; all four individuals showed minimal Ba/Ca values between ~1.2–1.8 years, consistent with field reports of the cessation of suckling. Enamel Sr/Ca did not support patterns of previous LA-ICP-MS spot sampling as the enamel rarely showed discrete Sr/Ca secretory zonation. Increases in Sr/Ca appeared in coronal dentine beginning ~0.3 years, with varied peak value ages (~0.7–2.7 years) and no evidence of a predicted postweaning decline.

Discussion
Inferences of baboon weaning ages from initial Ba/Ca minima are more congruent with behavioral observations than Sr/Ca maxima; this is consistent with studies of captive macaques of known weaning ages. Elemental variation is more apparent in the coronal dentine than the enamel of these baboons, which may relate to its more rapid mineralization and protection from the oral environment. Inferences of nursing histories from enamel Sr/Ca patterns alone should be reconsidered, and elevated values of Ba/Ca and Sr/Ca in teeth formed after weaning require further study.

Citation

Smith, T. M., Arora, M., Bharatiya, M., Dirks, W., & Austin, C. (2023). Elemental models of primate nursing and weaning revisited. American Journal of Biological Anthropology, 180(1), 216-223. https://doi.org/10.1002/ajpa.24655

• Journal Article Type: Article
• Acceptance Date: Nov 1, 2022
• Online Publication Date: Nov 20, 2022
• Publication Date: 2023-01
• Deposit Date: Sep 27, 2023
• Publicly Available Date: Sep 27, 2023
• Journal: American Journal of Biological Anthropology
• Electronic ISSN: 2692-7691
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 180
• Issue: 1
• Pages: 216-223
• DOI: https://doi.org/10.1002/ajpa.24655
• Public URL: https://durham-repository.worktribe.com/output/1750726