A single sample from the vasodentin layer was tested for collagen content, and results showed that no collagen was preserved in the tooth. As is common in tropical environments, postdepositional diagenetic processes affected the collagen within the tooth, a fact further complicated by the specimen’s deposition in a cenote where it was submerged for thousands of years, causing the leaching of collagen. In this case, because of the lack of collagen, dentin was used as a replacement, as has been done in previous studies (28, 41). Although this has not been specified in previous studies, to ensure that the results were accurate, we only sampled the inner orthodentin layer, the portion of bioapatite expected to be most resistent to diagenesis. All cracks in the tooth, where contaminants could infiltrate the inner orthodentin layer, were avoided. Approximately 200 mg of inner orthodentin was drilled from the tooth, and 25 ml of 0.1 M acetic acid was added using a modified procedure designed to minimize isotopic exchange between apatite structural carbonate and modern air CO2 and diagenetic carbonate during acid treatment. During reaction under vacuum, small CO2 bubbles expand rapidly and are evacuated. Repressurization with N2 from a liquid N2 vessel guarantees exclusion of 14C-enriched air CO2 while forcing the acid deeper into the orthodentin microstructure. Cycling between vacuum for ca. 15 to 20 min and brief repressurization with N2 continued until the sample ceased to produce CO2 bubbles under vacuum (2 to 3 hours). The sample was rinsed four times with distilled water and freeze-dried. In the ISGS radiocarbon Laboratory, the sample was reacted with phosphoric acid to release apatite carbonate CO2 and was cryogenically distilled. Radiocarbon dating was performed at the W. M. Keck Carbon Cycle Accelerator Mass Spectrometry Laboratory, University of California, Irvine. The dates were calibrated using IntCal13 (42).

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