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2.12. Food and Diet Analysis

2.12. Food and Diet Analysis. Important aspect in archaeology is migration and trade; isotope analysis of human remains such as bone and teeth delivers important information on diet & origin. . Isotope distribution in teeth

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2.12. Food and Diet Analysis

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  1. 2.12. Food and Diet Analysis Important aspect in archaeology is migration and trade; isotope analysis of human remains such as bone and teeth delivers important information on diet & origin. Isotope distribution in teeth and bone reflects characteristic isotope ratios (C, N, O, Sr) in food and water from local habitat. Teeth mineralize at early age, maintaining the isotopic signature from early age in teeth enamel. Dentin and bones adopt every twenty years. Comparison of teeth and bone isotope ratios indicates changes if a person has drastically changed its habitat.

  2. Depth analysis in teeth tooth enamel is formed in early childhood  origin dentin & bone changes with time  death Drilling and sequential isotope ratio analysis reveals fine structure, possibly due to migration habits.

  3. World wide 18O/16O distribution

  4. Fractionation Natural chemical or physical processes can fractionate the carbon, nitrogen, or oxygen isotopes during the up-take and alter the 13C/12C, 15N/14N, and 18O/16O isotopic ratios. This requires correction. e.g. photosynthesis enriches lighter isotopes → carbon in plant has relatively higher 12C/13C ratio than atmosphere. 18O/16O ratio fractionates by weight, the ratio decreases with altitude and with distance to coast due to weight difference in isotopes Fractionation is expressed in terms of δ13C which is a measure (in parts of a thousand ppm) of the deviation of the isotopic ratio 13C/12C from a standard material (PDB belemnitella americana). Typical δ13C vary between +2ppm to -27ppm and need to be determined for the material to be dated. Additional fractionation may occur during the chemical preparation of the sample.

  5. Fractionation effects fractionation term δ13C is defined from 13C/12C isotopic ratios for the sample (sm) and the standard (st) as: A negative value δ13C means that the sample is isotopically lighter than the standard probe. The standard is the fossil belemnite from the Pee Dee formation in South Carolina, PDB, (13C/12C)PDB = 0.0112372. A positive value means that the sample is enriched in the heavier isotope components.

  6. The δ13C Map Global mean value =-23.23

  7. C4-photosynthesis C3-photosynthesis sample number Excursion: fractionation and eating habits and its impact on human isotope ratios There are two different processes of photochemical assimilation of CO2 in plants (photosynthesis cycles).This leads to different carbon fractionation values δ13C in plants an the associated food chains ranging from δ13C =-26.5‰ (C3) to δ13C= -12.5 ‰ (C4). C3 plants dominate the northern cooler regions of Europe and North America. The habitat of C4 plants are the warmer regions in South- and Central America, Africa, and Australia.

  8. bicarbonate in ocean water and in ground pure C4 eaters CO2 in air bones of plant- eaters bones of meat- eaters human bones plants plants pure C3 eaters plant eater or animals Fractionation in food chain processes enrichment in δ13C in bone collage N. Van der Merve, American Scientist 70 (1982) 596

  9. North American Values North American plants are predominantly C3 plants  fractionation values of δ13C = -21.4 are observed in bone collages of plant and meat eating animals. If additional C4 plants - like corn – are consumed than will the δ13C value increase accordingly. e.g. ≈10% corn  δ13C ≈ -20 ‰. Pure maize diet will result in δ13C ≈ -10 ‰. Is sea food consumed, drastic changes occur since the ocean food chain is characterized by different fractionation processes leading to δ13C ≈ -18 ‰.

  10. fraction of C4 plant consumption in % BC time [y] AD Ancient eating habits The fractionation analysis of bone material with parallel 14C dating can help to identify changing eating habits. Example: increase of corn consumption (C4 plant) by population due to the corn migration into North America. The values result from bone analysis of human skeletons. At 1500 AD: ~75% corn consumption. N. Van den Merve, J. Vogel, Nature, 276 (1978) 815

  11. bicarbonate in ocean water and in ground CO2 in air plankton similar C3 (-17.8) nutrition bone material of coastal residents ocean proteins 100% from sea mammals fish, crabs, and coastal fauna bone material of inland residents C3 consumer 100% from land (C3) land fauna animal meat birds, fresh water fish Sea food chains

  12. Analysis of skeletons of early population of coastal British Columbia: δ13C=-13.4±0.9‰  ≈100% seafood based nutrition Analysis of skeletons of early population of Ottawa region: δ13C=-19.6±0.9‰  ≈ 100% C3 originated nutrition. Analysis of skeletons of early population of central British Columbia: δ13C=-15.4±0.3‰  ≈65% seafood (salmon) & ≈35% C3 originated nutrition. Observations

  13. vegetable maize Development of Mayan diet From fish and vegetable towards maize dominated food Demonstrated on a nitrogen/ carbon isotope ratio study Tykot et al. Arch. Chemistry 625 (1996) 355-365

  14. Meso-American food characteristicsduring the classical period Local differences can be detected for isotope ratios in human bone collages. Drastic differences due to corn or fish diet!

  15. Checking on Yax K’uk Mo 5th century AD the City of Copan in southern Yucatan converted from a small village to a center of Mayan culture within only decades through installation of Yax K’uk Mo as local ruler (coronation 9. 5. 426 AD). Origin of Yax K’uk Mo is unknown! Speculation is that he was installed by Teotihuacán (Central Mexico) to extend its political influence south. Main indicator “Goggles”

  16. Strontium Sr isotope ratio in upper incisor Ratio 87Sr/86Sr is an important indicator for tooth analysis Strontium Sr behaves chemically similar to Calcium Ca in tooth enamel (formed during the early childhood). Sr can replace Ca by food intake. Isotopic ratio reflects origin. 87Sr/86Sr = 0.7084 C. Day, Physics Today 57 (2004) 20-21

  17. Origin of 87Sr/86Sr Stable Strontium Sr isotopes: 84Sr (0.56%) 86Sr (9.86%), 87Sr (6.94%), 88Sr (82.58%) -decay 87Ru 87Sr T1/2=4.71010 y 86,87Sr are stable isotopes, 87Sr/86Sr=0.704 Stable 87Sr is enriched by decay of 87Rb. An environment with high Rb content therefore causes high 87Sr/86Sr ratio!

  18. Development of Sr isotope ratios in Yucatan Abundance of non-radioactive 86Sr in mineral is constant. 87Sr is stable but continuously produced by decay of the radioactive 87Rb (T1/2=48.8 Gy). Continental rock is rich in 87Rb, limestone contains little 87Rb. D. A. Hodell et al., J. Arch. Sci 31 (2004) 585-601

  19. Central Mexico is volcanic origin low Ca/Rb content 47 Yucatan peninsula formed by Ca/Rb containing Marine sediments  87Sr enrichment declining south. 87Sr/86Sr distribution in Mexico

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