Editing Isotope analysis (section)

==== Reconstructing ancient diets ====

[[Archaeology|Archaeological]] materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. [[Carbon]], [[nitrogen]] and [[zinc]] isotope ratios are used to investigate the diets of past people; these isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.<ref name="hermes_2018">{{cite journal|last1=Hermes|first1=Taylor R.|last2=Frachetti|first2=Michael D.|last3=Bullion|first3=Elissa A.|last4=Maksudov|first4=Farhod|last5=Mustafokulov|first5=Samariddin|last6=Makarewicz|first6=Cheryl A.|title=Urban and nomadic isotopic niches reveal dietary connectivities along Central Asia's Silk Roads|journal=Scientific Reports|date=26 March 2018|volume=8|issue=1|pages=596|doi=10.1038/s41598-018-22995-2|pmid=29581431|pmc=5979964|language=En|issn=2045-2322|bibcode=2018NatSR...8.5177H}}</ref>

Carbon isotopes are analysed in archaeology to determine the source of carbon at the base of the foodchain. Examining the [[Carbon 12|<sup>12</sup>C]]/[[Carbon 13|<sup>13</sup>C]] isotope ratio, it is possible to determine whether animals and humans ate predominantly [[C3 carbon fixation|C3]] or [[C4 carbon fixation|C4]] plants.<ref>{{Cite journal|last=van der Merwe|first=Nikolaas J.|date=1982|title=Carbon Isotopes, Photosynthesis, and Archaeology: Different pathways of photosynthesis cause characteristic changes in carbon isotope ratios that make possible the study of prehistoric human diets|jstor=27851731|journal=American Scientist|volume=70|issue=6|pages=596–606|bibcode=1982AmSci..70..596V}}</ref> Potential C3 food sources include [[wheat]], [[rice]], [[tuber]]s, [[fruit]]s, [[Nut (fruit)|nuts]] and many [[vegetable]]s, while C4 food sources include millet and sugar cane.<ref>{{Cite journal|last=O'Leary|first=Marion H.|date=1988|title=Carbon Isotopes in Photosynthesis|jstor=1310735|journal=BioScience|volume=38|issue=5|pages=328–336|doi=10.2307/1310735}}</ref> Carbon isotope ratios can also be used to distinguish between marine, freshwater, and terrestrial food sources.<ref>{{Cite journal|last1=Schoeninger|first1=Margaret J|author-link=Margaret Schoeninger|last2=DeNiro|first2=Michael J|title=Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals|journal=Geochimica et Cosmochimica Acta|volume=48|issue=4|pages=625–639|doi=10.1016/0016-7037(84)90091-7|bibcode=1984GeCoA..48..625S|year=1984}}</ref><ref>{{Cite book|title=Stable Isotopes in Ecological Research|last1=Fry|first1=B.|last2=Sherr|first2=E. B.|chapter=δ13C Measurements as Indicators of Carbon Flow in Marine and Freshwater Ecosystems |date=1989|publisher=Springer, New York, NY|isbn=9781461281276|series=Ecological Studies|volume=68 |pages=196–229|language=en|doi=10.1007/978-1-4612-3498-2_12}}</ref>

Carbon isotope ratios can be measured in bone [[collagen]] or bone mineral ([[hydroxylapatite]]), and each of these fractions of bone can be analysed to shed light on different components of diet. The carbon in bone collagen is predominantly sourced from dietary protein, while the carbon found in bone mineral is sourced from all consumed dietary carbon, included carbohydrates, lipids, and protein.<ref>{{Cite journal|last1=Fernandes|first1=Ricardo|last2=Nadeau|first2=Marie-Josée|last3=Grootes|first3=Pieter M.|date=2012-12-01|title=Macronutrient-based model for dietary carbon routing in bone collagen and bioapatite|journal=Archaeological and Anthropological Sciences|language=en|volume=4|issue=4|pages=291–301|doi=10.1007/s12520-012-0102-7|bibcode=2012ArAnS...4..291F |s2cid=85014346|issn=1866-9557}}</ref>

Nitrogen isotopes can be used to infer soil conditions, with enriched [[δ15N]] used to infer the addition of [[manure]]. A complication is that enrichment also occurs as a result of environmental factors, such as wetland [[denitrification]], [[salinity]], [[aridity]], [[microbes]], and [[Deforestation|clearance]].<ref>{{cite book|last1=Lodwick|first1=Lisa|author-link1=Lisa Lodwick|last2=Stroud|first2=Elizabeth|chapter=Paleoethnobotany and Stable Isotopes|editor-last1=López Varela|editor-first1=Sandra L.|title=The Encyclopedia of Archaeological Sciences|year=2019|pages=1–4 |publisher=Wiley-Blackwell|place=Malden, MA|doi=10.1002/9781119188230.saseas0436|isbn=9780470674611 |s2cid=239512474 }}</ref> δ13C and δ15N measurements on medieval manor soils has shown that stable isotopes can differentiate between crop cultivation and grazing activities, revealing land use types such as cereal production and the presence of fertilization practices at historical sites.<ref>{{Cite journal |last1=Janovský |first1=Martin P. |last2=Ferenczi |first2=Laszlo |last3=Trubač |first3=Jakub |last4=Klír |first4=Tomáš |date=2024-06-26 |title=Stable isotope analysis in soil prospection reveals the type of historic land-use under contemporary temperate forests in Europe |journal=Scientific Reports |language=en |volume=14 |issue=1 |pages=14746 |doi=10.1038/s41598-024-63563-1 |pmid=38926400 |pmc=11208554 |bibcode=2024NatSR..1414746J |issn=2045-2322}}</ref>

To obtain an accurate picture of palaeodiets, it is important to understand processes of [[diagenesis]] that may affect the original isotopic signal. It is also important for the researcher to know the variations of isotopes within individuals, between individuals, and over time.<ref name="hermes_2018" />