172-9 Tooth enamel nanocrystals became more misoriented after the introduction of meat and agriculture

Session: Urban Geochemistry

Presenting Author:

Authors:

Abstract:

Tooth enamel, the hardest vertebrate tissue, consists of thin, elongated hydroxyapatite nanocrystals (Ca₅(PO₄)₃OH). During the past two million years, human teeth became smaller, with thinner enamel and more pronounced decussation patterns, paralleling brain expansion, facial reduction, language, culture, and three dietary shifts: increased meat consumption (~2.0–1.5 million years before present (BP)), agriculture (~12,000 BP), and industrialization (~200 BP). Using a new method, Polarization Enabled Large Input of Crystal Angles at the Nanoscale (PELICAN), we examined enamel nanostructure in 12 primate teeth (17.8 Ma, 9 species). Adjacent enamel nanocrystals show small mode misorientation angles, enhancing crack deflection and therefore toughness [1]. Misorientation of adjacent nanocrystals increased 1.5× and 1.9x, respectively, with the introduction of meat and agriculture [2], but not with industrialization. Within recent Homo sapiens (0-2000 BP), PELICAN reveals consistent mode misorientations across the same tooth and across individuals. These results indicate that dietary shifts influenced enamel architecture down to the nanoscale, informing design principles for crack-resistant, bioinspired materials, and shedding light on the evolution of the human lineage.

1.         E Beniash et al., Nat Commun (2019), DOI: https://doi.org/10.1038/s41467-019-12185-7

2.         PUPA Gilbert et al., submitted. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10723

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