DOI: 10.5061/dryad.3j9kd51nz
title: Supplementary Data for: Life history in primate teeth is revealed by changes in major and minor element concentrations measured via field-emission SEM-EDS analysis

description: Overcoming the non-specificity of histological accentuated growth lines in
 hard tissues is an ongoing challenge. Identifying season at death and
 reproductive events has profound implications for evolutionary, ecological
 and conservation studies. Dental cementum is a mineralized tissue with
 yearly periodicity that continues deposition from tooth formation until
 death, maintaining a record spanning almost the entire life of an
 individual. Recent work has successfully employed elemental analysis of
 calcified incremental tissues to detect changes in extrinsic conditions
 such as diet and climate and to identify two important life history
 milestones: weaning and sexual maturity. Here, we employ field-emission
 scanning electron microscopy and energy-dispersive X-ray analysis to
 measure the relative concentrations of calcium, phosphorous, oxygen,
 magnesium and sodium in the cementum of 34 teeth from seven male and
 female rhesus macaques with known medical and life history information. We
 find that changes in relative magnesium concentrations correspond with
 reproductive events in females and breastfeeding in infants. Additionally,
 we observe seasonal calcium patterns in 77.3% of the samples.
description: All data were collected using a Bruker Quantax 200 XFlash 6160
 EDS detector (Bruker, Billerica, MA, USA), coupled with a Zeiss Gemini-300
 FE-SEM (Carl Zeiss Microscopy, White Plains, NY, USA). We acquired data in
 high vacuum mode, with an accelerating voltage of 15kV and an electron
 beam aperture of 60μm, in high current mode and with a working distance of
 8.5mm, which is the analytical working distance of this setup.
 We chose our regions of interest (ROI) on the cervical third of
 the root. For each specimen we acquired line scan spectra across the
 entire thickness of the cementum, starting from the cementum-dentine
 junction (CDJ). Prior to collecting data, we confirmed that the surface
 was free of topographic relief. The spot size of the line scan was set to
 match the radius of the interaction volume of the beam, which was
 consistently ~0.75μm. The scan dwell time was 64μs, and the spectrometer
 throughput 275Kcps. To have at least 10,000 counts per peak, scan time was
 manually determined for each specimen since they varied in cementum
 thickness. We used the zero kV peak to align the spectra and the P/B-ZAF
 standardless analysis quantification model in interactive mode to validate
 each peak. We only accepted as peaks those that were at least 3 standard
 deviations greater than the background. Carbon (C), oxygen (O), sodium
 (Na), P, Ca and Mg were detected with sufficient counts per peak in all
 samples. For each point across the cementum transect, using the software
 Bruker Esprit 2.3, we recorded the total net (NETTO) counts for each
 element.  Data analysis was performed using R v.3.6.3.
 Within each datafile we added the variables derived from the recorded life
 histories (Supplementary Methods): Age, Event / Event Category (Table S2),
 Month and Season. The age at each point was derived by scaling the total
 thickness of the cementum to the range of years during which cementum was
 deposited and then adding the age at cementum initiation specific to the
 chosen ROI (reported for each tooth in Table S3). Since
 our samples were carbon-coated the elemental percentages are altered,
 allowing only the collection of relative proportions of the elements.
 Therefore, we pre-processed our data in two different ways (both datasets
 are available here), aimed at addressing different questions:
 For predictions 1 and 4: Within each data file, we
 normalized the data for each element to a 0-1 range. Instead of providing
 information regarding the relationships between elements at each point in
 time, it provides information regarding the behavior of a single element
 over time. For predictions 2 and 3: Within each data
 file, we eliminated the values for C and then calculated the percent
 concentration for each element at each acquisition point. The resulting
 relative percent concentrations reveal how changes in the concentration of
 one element are correlated with those of the others. This allows for the
 analysis of the simultaneous behavior of several elements as their
 numerical relationship is maintained, even if the values are increased by
 the absence of C.
description: None