We would like to thank the Max Planck Society for funding this research as well as the recent setting up of a Stable Isotope laboratory at the Department Archaeology, Max Planck Institute for the Science of Human History.

The following protocol follows the guidelines of the Light Isotope Mass Spectrometry Laboratory at the Max Planck Institute for the Science of Human History. Appropriate ethics permissions from national and international committees should be sought for analyses involving endangered modern or historical faunal specimens, and for the use of archaeological and faunal material of interest to contemporary stakeholders. In this paper, the samples used were archaeological and fossil specimens. No living humans were used in this...

<ol>
	<li>Balasse, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reconstructing+dietary+and+environmental+history+from+enamel+isotopic+analysis:+time+resolution+of+intra-tooth+sequential+sampling.">Reconstructing dietary and environmental history from enamel isotopic analysis: time resolution of intra-tooth sequential sampling.</a> International Journal of Osteoarchaeology. 12 (3), 155-165 (2002).</li><li>Balasse, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+biases+in+sampling+design+and+interpretation+of+intra-tooth+isotope+analysis.">Potential biases in sampling design and interpretation of intra-tooth isotope analysis.</a> International Journal of Osteoarchaeology. 13 (1-2), 3-10 (2003).</li><li>Lee-Thorp, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+isotopes+and+old+bones.">On isotopes and old bones.</a> Archaeometry. 50 (6), 925-950 (2008).</li><li>Clementz, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+insight+from+old+bones:+stable+isotope+analysis+of+fossil+mammals.">New insight from old bones: stable isotope analysis of fossil mammals.</a> Journal of Mammalogy. 93 (2), 368-380 (2012).</li><li>Loftus, E., Roberts, P., Lee-Thorp, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+isotopic+generation:+four+decades+of+stable+isotope+analysis+in+African+archaeology.">An isotopic generation: four decades of stable isotope analysis in African archaeology.</a> Azania: Archaeological Research in Africa. 51 (1), 88-114 (2016).</li><li>Ventresca Miller, A. R., Makarewicz, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isotopic+approaches+to+pastoralism+in+prehistory:+Diet,+mobility,+and+isotopic+reference+sets.">Isotopic approaches to pastoralism in prehistory: Diet, mobility, and isotopic reference sets.</a> Isotopic Investigations of Pastoralism in Prehistory. , 1-14 (2018).</li><li>Hollund, H. I., Ariese, F., Fernandes, R., Jans, M. M. E., Kars, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Testing+an+alternative+high-throughput+tool+for+investigating+bone+diagenesis:+FTIR+in+attenuated+total+reflection+(ATR)+mode.">Testing an alternative high-throughput tool for investigating bone diagenesis: FTIR in attenuated total reflection (ATR) mode.</a> Archaeometry. 55 (3), 507-532 (2013).</li><li>LeGeros, R. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+phosphates+in+oral+biology+and+medicine.">Calcium phosphates in oral biology and medicine.</a> Monographs in oral sciences. 15, 109-111 (1991).</li><li>Lee-Thorp, J. L., Van Der Merwe, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbon+isotope+analysis+of+fossil+bone+apatite.">Carbon isotope analysis of fossil bone apatite.</a> South African Journal of Science. 83 (11), 712-715 (1987).</li><li>Cerling, T. E., Harris, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbon+isotope+fractionation+between+diet+and+bioapatite+in+ungulate+mammals+and+implications+for+ecological+and+paleoecological+studies.">Carbon isotope fractionation between diet and bioapatite in ungulate mammals and implications for ecological and paleoecological studies.</a> Oecologia. 120 (3), 347-363 (1999).</li><li>Koch, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isotopic+study+of+the+biology+of+modern+and+fossil+vertebrates.">Isotopic study of the biology of modern and fossil vertebrates.</a> Stable Isotopes in Ecology and Environmental Science. , 99-154 (2007).</li><li>Nelson, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Wheeler's Dental Anatomy, Physiology and Occlusion-E-Book. , (2014).</li><li>Tsutaya, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+cradle+to+grave:+multi-isotopic+investigations+on+the+life+history+of+a+higher-status+female+from+Edo-period+Japan.">From cradle to grave: multi-isotopic investigations on the life history of a higher-status female from Edo-period Japan.</a> Anthropological Science. 124 (3), 185-197 (2016).</li><li>Sponheimer, M., Passey, B. H., De Ruiter, D. J., Guatelli-Steinberg, D., Cerling, T. E., Lee-Thorp, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isotopic+evidence+for+dietary+variability+in+the+early+hominin+Paranthropus+robustus.">Isotopic evidence for dietary variability in the early hominin Paranthropus robustus.</a> Science. 314 (5801), 980-982 (2006).</li><li>Lee-Thorp, J., Sponheimer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three+case+studies+used+to+reassess+the+reliability+of+fossil+bone+and+enamel+isotope+signals+for+paleodietary+studies.">Three case studies used to reassess the reliability of fossil bone and enamel isotope signals for paleodietary studies.</a> Journal of Anthropological Archaeology. 22 (3), 208-216 (2003).</li><li>Zazzo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+and+enamel+carbonate+diagenesis:+a+radiocarbon+prospective.">Bone and enamel carbonate diagenesis: a radiocarbon prospective.</a> Palaeogeography, Palaeoclimatology, Palaeoecology. 416, 168-178 (2014).</li><li>Sponheimer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Isotopic paleoecology of the Makapansgat Limeworks fauna (Australopithecus africanus, South Africa). , (1999).</li><li>Sponheimer, M., Lee-Thorp, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alteration+of+enamel+carbonate+environments+during+fossilization.">Alteration of enamel carbonate environments during fossilization.</a> Journal of Archaeological Science. 26 (2), 143-150 (1999).</li><li>Roche, D., S&#233;galen, L., Balan, E., Delattre, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preservation+assessment+of+Miocene-Pliocene+tooth+enamel+from+Tugen+Hills+(Kenyan+Rift+Valley)+through+FTIR,+chemical+and+stable-isotope+analyses.">Preservation assessment of Miocene-Pliocene tooth enamel from Tugen Hills (Kenyan Rift Valley) through FTIR, chemical and stable-isotope analyses.</a> Journal of Archaeological Science. 37 (7), 1690-1699 (2010).</li><li>Roberts, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calling+all+archaeologists:+guidelines+for+terminology,+methodology,+data+handling,+and+reporting+when+undertaking+and+reviewing+stable+isotope+applications+in+archaeology.">Calling all archaeologists: guidelines for terminology, methodology, data handling, and reporting when undertaking and reviewing stable isotope applications in archaeology.</a> Rapid Communications in Mass Spectrometry. , (2018).</li><li>Snoeck, C., Pellegrini, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparing+bioapatite+carbonate+pre-treatments+for+isotopic+measurements:+Part+1-Impact+on+structure+and+chemical+composition.">Comparing bioapatite carbonate pre-treatments for isotopic measurements: Part 1-Impact on structure and chemical composition.</a> Chemical Geology. 417, 394-403 (2015).</li><li>Pellegrini, M., Snoeck, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparing+bioapatite+carbonate+pre-treatments+for+isotopic+measurements:+Part+2-Impact+on+carbon+and+oxygen+isotope+compositions.">Comparing bioapatite carbonate pre-treatments for isotopic measurements: Part 2-Impact on carbon and oxygen isotope compositions.</a> Chemical Geology. 420, 88-96 (2016).</li><li>Wright, L. E., Schwarcz, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+carbon+and+oxygen+isotopes+in+human+tooth+enamel:+identifying+breastfeeding+and+weaning+in+prehistory.">Stable carbon and oxygen isotopes in human tooth enamel: identifying breastfeeding and weaning in prehistory.</a> American Journal of physical anthropology. 106 (1), 1-18 (1998).</li><li>Roberts, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fruits+of+the+forest:+Human+stable+isotope+ecology+and+rainforest+adaptations+in+Late+Pleistocene+and+Holocene+(&#8764;+36+to+3+ka)+Sri+Lanka.">Fruits of the forest: Human stable isotope ecology and rainforest adaptations in Late Pleistocene and Holocene (&#8764; 36 to 3 ka) Sri Lanka.</a> Journal of human evolution. 106, 102-118 (2017).</li><li>Zazzo, A., Balasse, M., Patterson, W. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+&#948;13C+intratooth+profiles+in+bovine+enamel:+Implications+for+mineralization+pattern+and+isotopic+attenuation.">High-resolution &#948;13C intratooth profiles in bovine enamel: Implications for mineralization pattern and isotopic attenuation.</a> Geochimica et Cosmochimica Acta. 69 (14), 3631-3642 (2005).</li><li>Sydney-Zax, M., Mayer, I., Deutsch, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbonate+content+in+developing+human+and+bovine+enamel.">Carbonate content in developing human and bovine enamel.</a> Journal of dental research. 70 (5), 913-916 (1991).</li><li>Rink, W. J., Schwarcz, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tests+for+diagenesis+in+tooth+enamel:+ESR+dating+signals+and+carbonate+contents.">Tests for diagenesis in tooth enamel: ESR dating signals and carbonate contents.</a> Journal of Archaeological Science. 22 (2), 251-255 (1995).</li><li>Szpak, P., Metcalfe, J. Z., Macdonald, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Best+practices+for+calibrating+and+reporting+stable+isotope+measurements+in+archaeology.">Best practices for calibrating and reporting stable isotope measurements in archaeology.</a> Journal of Archaeological Science: Reports. 13, 609-616 (2017).</li><li>Wright, L. E., Schwarcz, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correspondence+between+stable+carbon,+oxygen+and+nitrogen+isotopes+in+human+tooth+enamel+and+dentine:+infant+diets+at+Kaminaljuyu.">Correspondence between stable carbon, oxygen and nitrogen isotopes in human tooth enamel and dentine: infant diets at Kaminaljuyu.</a> Journal of Archaeological Science. 26 (9), 1159-1170 (1999).</li><li>Schoeninger, M. J., Hallin, K., Reeser, H., Valley, J. W., Fournelle, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isotopic+alteration+of+mammalian+tooth+enamel.">Isotopic alteration of mammalian tooth enamel.</a> International Journal of Osteoarchaeology. 13 (1-2), 11-19 (2003).</li></ol>

The authors declare no conflict of interest.

The challenges of successful sampling (bulk and incremental) of dentition relies on the access to knowledge regarding drilling techniques and sample preparation, alongside the investment in relatively inexpensive equipment. These challenges are easily surmountable when clear instructions are available concerning&#160;sampling and pretreatment approaches. In this article, we hope to have disseminated these in a clear, concise fashion for researchers new to these methods. Scholars applying these methods for the first time ...

Stable carbon and oxygen isotope analyses of tooth enamel carbonate has been used to study past human dietary intake, weaning, and mobility, as well as faunal reliance on vegetation, the movement of animals, and livestock foddering. These applications have been comprehensively discussed and reviewed for a variety of environmental conditions indicating the effects of local aridity, temperature, water sources, and vegetation compositions1,2,3,4,5,6. The diversity of potential applications in archaeology and paleontology, as well as the good preservation of tooth enamel carbonate, has made it an attractive material for stable isotope work3. Methods of sampling, pretreatment, and diagenesis screening are briefly described in a number of previous publications1,7. However, thorough verbal and visual demonstrations remain largely unavailable, particularly to people outside of archaeological science laboratories and among laboratory groups with limited funding where the interest in the use of this technique is increasing5.
Tooth enamel is primarily made up of hydroxyapatite (bioapatite) crystallites8 larger than those in bone, making it more resistant to post-mortem diagenetic ionic substitutions and contamination3. Modern studies have demonstrated that stable carbon isotope (&#948;13C) measurements of faunal tooth enamel reliably record animal diet and behavior9,10. The stable oxygen isotope (&#948;18O) value of tooth enamel is determined by the oxygen isotopic composition of ingested water, which includes water in plant and animal foods, drinking water, respiration, as well as various environmental impacts on the water which can lead to further isotopic fractionation (e.g., aridity, temperature, altitude, rainfall amount, continental location)11. This has made it a popular method for dietary and environmental reconstruction in archeological, paleoecological, and paleontological research.
The period of tooth enamel formation is relatively short (years) and differs depending on the tooth being sampled. For humans, first molar enamel mineralizes between birth and 3 years of age, premolars mineralize between 1.5 and 7 years of age, second molars mineralize between 2.5 and 8 years of age, and third molars mineralize during adolescence, between 7 and 16 years12. Given that tooth enamel forms incrementally over its period of formation, it can be sampled in bulk along the entire growth axis or sampled sequentially in order to investigate the changes in diet and environment that have occurred during the formation period13. Chronologically-ordered dietary change within a given tooth is observable for humans and other animals1,14, providing information regarding inter-annual seasonal and dietary variation.
While enamel is usually resistant to diagenesis, isotopic modifications resulting from the burial environment are possible and have been observed15,16, making experimental checks and pretreatment choices useful. While it is not the only available method, Fourier transform infrared spectroscopy (FTIR), particularly in Attenuated Transmission Mode, has emerged as a quick, inexpensive, and relatively accessible method for assessing taphonomic alteration in tooth enamel, particularly in paleontological contexts17,18,19,20. However, detailed protocols and recording standards remain relatively inaccessible to many people outside the fields of geochemistry or material science.
Reaction times and the chemicals employed by researchers in the pretreatment of tooth enamel also vary considerably in the literature, often with limited consideration as to what this variability may do to stable carbon and oxygen isotope values of the sample21,22. Here, we report an approach that uses dilute acetic acid (0.1 M) for the pretreatment of enamel powder samples. However, given that the differences in isotopic measurements resulting from pretreatment are relatively minor for tooth enamel, it is best for the researchers to follow the protocols for datasets with which they wish to compare their data to11. Furthermore, where small sequential samples are taken, particularly on Holocene samples, no pretreatment may be chosen (following pilot diagenetic tests) to avoid sample wastage.
Although the methods we report here are by no means new, to our knowledge, this is the first time that a thorough written and visual documentation of bulk and sequential sampling, pretreatment choices, and diagenetic check methods (in the form of FTIR) for tooth enamel have been made widely available to a varied academic audience. While we hope our efforts will make this approach more easily accessible to a wider number of individuals and laboratories, researchers who want to apply and publish this technique must be aware of minimum reporting standards, diagenetic considerations, and presentation requirements overviewed elsewhere20, as well as potential interpretive complexities that will be unique to their study region, taxa analyzed, and time period5.

<table>
	<tbody>
		<tr>
			<td>Dremel Micro</td>
			<td>Dremel</td>
			<td></td>
			<td>https://www.dremel.com/en_US/products/-/show-product/tools/8050-micro</td>
		</tr>
		<tr>
			<td>Diamond-tipped drill bit</td>
			<td>Dremel</td>
			<td></td>
			<td>https://www.dremel.com/en_US/products/-/show-product/accessories/7122-diamond-wheel-point</td>
		</tr>
		<tr>
			<td>1.5 mL micro-centrifuge tube</td>
			<td>Sigma Aldrich</td>
			<td></td>
			<td>https://www.sigmaaldrich.com/catalog/product/sigma/t2422?lang=de&#38;region=DE&#38;gclid=EAIaIQobChMI7pHRpauW2QIV77ftCh1p1wjhEAAYASAAEgKzkvD_BwE</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td></td>
			<td></td>
			<td>Linear Formula:&#160;CH3OH</td>
		</tr>
		<tr>
			<td>Acetic Acid</td>
			<td></td>
			<td></td>
			<td>Linear Formula:&#160;CH3CO2H</td>
		</tr>
		<tr>
			<td>Dremel rig set-up (workstation)</td>
			<td>Dremel</td>
			<td></td>
			<td>https://www.dremel.com/en_US/products/-/show-product/tools/220-01-workstation</td>
		</tr>
		<tr>
			<td>Microcentrifuge</td>
			<td>Thermo Scientific</td>
			<td></td>
			<td>http://www.thermofisher.com/order/catalog/product/75002401</td>
		</tr>
		<tr>
			<td>Mini-centrifuge</td>
			<td>Sprout</td>
			<td></td>
			<td>http://www.heathrowscientific.com/sprout-mini-centrifuge-4</td>
		</tr>
		<tr>
			<td>Freeze drier</td>
			<td>Zirbus Technology</td>
			<td></td>
			<td>http://www.zirbus.com</td>
		</tr>
	</tbody>
</table>

sampling and pretreatment of tooth enamel carbonate for stable carbon and oxygen isotope analysis

Stable carbon and oxygen isotope analysis of human and animal tooth enamel carbonate has been applied in paleodietary, paleoecological, and paleoenvironmental research from recent historical periods back to over 10 million years ago. Bulk approaches provide a representative sample for the period of enamel mineralization, while sequential samples within a tooth can track dietary and environmental changes during this period. While these methodologies have been widely applied and described in archaeology, ecology, and paleontology, there have been no explicit guidelines to aid in the selection of necessary lab equipment and to thoroughly describe detailed laboratory sampling and protocols. In this article, we document textually and visually, the entire process from sampling through pretreatment and diagenetic screening to make the methodology more widely available to researchers considering its application in a variety of laboratory settings.

Using the sampling procedure presented above, incremental enamel bioapatite samples were prepared. The analysis of bioapatite in enamel depends on the accuracy of sampling, whether bulk or incremental. In this case, we have chosen to present the results of archaeological samples (two sheep) from different climatic zones. Incremental samples were analyzed from sheep second molars and labelled starting at the ERJ (Figure 4). Incremental sample locations were nu...

Watch this Scientific Journal Video about Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis at JoVE.com

Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis

Stable carbon and oxygen isotope analysis of human and animal tooth enamel carbonate has been used as a proxy for individual diet and environmental reconstruction. Here, we provide a detailed description and visual documentation of bulk and sequential tooth enamel sampling as well as pretreatment of archaeological and paleontological samples.

Stable carbon and oxygen isotope analysis of human and animal tooth enamel carbonate has been applied in paleodietary, paleoecological, and ...

This method can answer key questions in archeology, paleontology, and ecology, such as domesticated animal diets, animal management strategies, and animal mobility. The main advantage of this technique is that it is relatively nondestructive and that it is focused on a material that is reasonably resistant to chemical changes in the burial environment. Individuals new to this method will struggle because there are no available visual aids for the sampling of paleontological and archeological remains of humans and animals.Visual demonstration of this method is critical because it is difficult to learn and practice on archeological materials is limited. To begin bulk sampling, set up a handheld drill as outlined in the text protocol, with a clean diamond-tipped drill of even shape, attached via a chuck to the drill setup. Using the drill, clean the outer surface of the tooth by gentle abrasion.Next, tare a 1.5-milliliter microcentrifuge tube on an appropriately accurate balance. Then, place clean aluminum foil or weighing paper under the drill to collect the enamel powder. Use the drill to deliver gentle and even abrasion, creating a groove parallel to the entire growth axis.Be aware that the amount of sample powder drilled will vary depending on the equipment used for analysis, the pretreatment protocol, and the size of the tooth. Collect the resulting enamel powder, and transfer it into a 1.5-milliliter microcentrifuge tube. Record both the sample number and enamel weight in a laboratory notebook, as well as an electronic database.After each tooth is drilled, clean any used drill bits using 0.5-molar hydrochloric acid on a robust tissue. Wash the drill bits again with an organic solvent on a new robust tissue. Clean the drill itself using either a vacuum or compressed air.Once a drilling session is complete, thoroughly clean the workspace using either a dedicated vacuum cleaner or a dustpan and brush. Wipe down the sampling space with methanol. Clean the drill using either the vacuum or compressed air.For sequential sampling, first clean the surface of the tooth by removing a very thin layer of outer tooth enamel. Choose an appropriate drill bit for the sample, as the width of the sampling line is determined by the diameter of the drill bit. To begin drilling, press the tooth enamel against the drill bit and apply pressure.Drill along the buccal surface perpendicular to the growth axis of the tooth, running from the enamel-root junction to the top of the crown. Make sure to drill from the apex to the base of the crown at the location of the enamel-root junction, resulting in a groove across the enamel layer. After the drilling is complete, weigh the sample to ensure there is enough enamel powder, and record the weight.Repeat the drilling process several times per tooth, with each consecutive line parallel to the previous sample line and about one to two millimeters apart. After this, use calipers to measure the distance of each sampling line from the enamel-root junction. Record each distance for comparison.To begin, use a pipette to add 0.1-molar acetic acid to each sample at a concentration of 0.1 milliliters per one milligram of enamel. Agitate the samples either by shaking or by using an agitator. Let the agitated samples sit for 10 minutes.Centrifuge the samples at 13, 700 g for two minutes. Using a clean pipette, replace the acetic acid with one milliliter of ultrapure water, and agitate either by shaking or by using an agitator. Centrifuge again at 13, 700 g for two minutes.Repeat the process of replacing the ultrapure water and centrifuging two additional times. Test the samples for neutrality. If the sample has not reached neutrality, repeat the washing process until it does.Then, use a pipette to remove the remaining fluid without disturbing the supernatant. Place a precut one centimeter by one centimeter square of Parafilm over each microcentrifuge tube. Using a sharp object, make a small hole in the Parafilm to ensure that the sample dries appropriately, and place the tubes in a freezer overnight.The next day, transfer the samples to the freeze dryer to remove any remaining fluid. Once the samples are dry, remove the Parafilm, and close the microcentrifuge lids. Check the tube labeling, and remark the tubes as necessary.In this study, incremental enamel bioapatite samples are prepared. Each incremental sample location is numbered, and the distance between each location and the enamel-root junction is measured. Diverse carbon and oxygen stable isotope results from two representative sheep confirm that these animals lived in different environments.Sheep A is from a tropical grassland and shows incremental oxygen 18 in a narrow range, between 3.3 and 5.1 per mil. This suggests ingestion of water from sources with similar isotopic values and a lack of strong seasonal shifts in precipitation. In contrast, sheep B, which is from a temperate dry steppe grassland, has oxygen 18 values with a high amplitude of variation, ranging from negative 5.2 to negative 13.1 per mil.This indicates strong seasonal variation in precipitation. Stable carbon isotope values suggest that sheep A's diet consists mainly of C4 plants, while sheep B's diet consists mainly of C3 vegetation. Incremental oxygen 18 and carbon 13 values for a human tooth from a rainforest environment are highly constrained.These values, which fall within a two per mil range, suggest a lack of variation in foraging strategies over the period of enamel mineralization. While attempting this procedure, it is important to remember to practice sequential sampling on modern teeth before drilling ancient samples that are not replaceable. Sequential sampling may take several hours of practice before proficiency is reached.For ancient samples, it is important to choose teeth that can withstand the sampling process. Teeth that are poorly preserved or are liable to crumble are unlikely to prove useful for detailed sequential sampling. Following this procedure, other methods such as strontium isotope analysis can be attempted in order to understand human and animal mobility.After its development, this technique paved the way for researchers in the fields of archeology and paleontology to explore animal herding and migration strategies across diverse regions and time periods. Don't forget that working with drills and acetic acid can be extremely hazardous, and precautions such as googles, gloves, and face masks should always be taken while performing this procedure.

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Research

JoVE Journal

Biochemistry

13.7K visualizações.  Max Planck Institute for the Science of Human History. This method can answer key questions in archeology, paleontology, and ecology, such as domesticated animal diets, animal management strategies, and animal mobility. The main advantage of this technique is that it is relatively nondestructive and that it is focused on a material that is reasonably resistant to chemical changes in the burial environment. Individuals new to this method will struggle because there are no available visual aids for the sampling of paleontological and archeological ...