Stable and radiogenic isotopes in Archaeology and Anthropology
Stable and radiogenic isotopes in Archaeology and Anthropology Henry P. Schwarcz Mc. Master University Hamilton, Ontario, Canada Christine White and Fred Longstaffe University of Western Ontario London, Ontario, Canada
Definitions (loose!) Anthropology: How people live (“culture”) Archaeology: How people Lived (prehistory and later) Paleoanthropology: Who “people” were (evolution)
The samples: Bones, teeth Time depth: 3 My to recent
Bone is a composite material consisting of: 60 wt% hydroxyapatite: HA Ca 5(PO 4, CO 3 ) 3 (OH, CO 3) OXYGEN CARBON + 40% collagen (protein) N, C ATOMS
Diagenesis: when bad things happen to good bones During burial: Collagen degrades: C/N ~ 3. 2? Hydroxyapatite “crystallinity” increases O, C isotopic exchange with soil-water? We can test for these and exclude bad bones
Stable isotopes can help inform: Paleodiet: “you are what you eat + x ‰” Migration: where did people come from? Paleoclimate: rain, drought, cold, heat
Stages of life recorded M 1 teeth M 2, P 1, etc M 3 bones hair, etc. death 0 10 20 30 40 years 50 60 70
PALEODIET Nutrient molecules: protein: C, N, H, O Fat: C, H, O Carbohydrate: C, H, O δ 13 C, δ 15 N, δ 18 O of each nutrient varies depending on the source
δ 15 N (‰) (AIR) C 4 PLANTS δ 13 C (‰) (PDB)
Isotopic. Analysis δ 13 C(bone collagen) = δ 13 C (food*) + 5‰ [* mainly dietary protein (? )] δ 13 C (CO 3 -apatite) ≈ δ 13 C (food) + 11 ‰ δ 15 N (collagen) = δ 15 N(diet) + 3 ‰ [“trophic level effect”]
Marine consumers: how far would you go for sushi? You are here
Walker and De. Niro Am. J. Phys Anth. , 1986 Seal Conclusion: Everyone was eating seal meat, but more in the islands
Los Angeles MALIBU site
Schwarcz & Walker, in prep. Walker & De. Niro Same trend as on Channel Islands: females have higher trophic level
Travelling foods: Maize arrives in Ontario ~ AD 700 Ma om r f ize ico x e M
After AD 700 maize replaced wild carbohydrates…
Paleoclimate Isotopes as indicators of Temperature: paleotemperatures Mollusk shells in middens Speleothems Teeth, bones Humidity, Rainfall δ 13 C C 3 vs C 4 plants (wet vs dry) δ 15 N in collagen: rainfall (aridity) δ 18 O cycles in tooth enamel: seasonality of rain
Paleoclimate Isotopes as indicators of Temperature: paleotemperatures Mollusk shells in middens Speleothems Teeth, bones Humidity, Rainfall δ 13 C C 3 vs C 4 plants (wet vs dry) δ 15 N in collagen: rainfall (aridity) δ 18 O cycles in tooth enamel: seasonality of rain
δ 18 O Paleotemperatures: Sclerochronology Isotopic cycles in marine shell carbonates Season of occupation of midden-sites Winter collection Matthieu et al. , Paleo 3, 2005
Paleoclimate Isotopes as indicators of Temperature: paleotemperatures Mollusk shells in middens Speleothems Teeth, bones Humidity, Rainfall δ 13 C C 3 vs C 4 plants (wet vs dry) δ 15 N in collagen: rainfall (aridity) δ 18 O cycles in tooth enamel: seasonality of rain
East Africa: calcite in soils C 3, moist----------C 4, hot, dry Levin et al. , EPSL, 2004
Migration: O and Sr isotopes Where does he/she come from? Isotopic labels can tell us something About place of origin (but not everything) These are questions in Archaeology/Anthropology Forensic Science (murder victims)
δ 18 O bone tells us δ 18 O of local drinking water δ 18 O(bone) δ 18 O(water)
δ 18 O of meteoric water varies regionally Decreases with Increasing latitude (poleward) Distance from sea (source of water vapor) Elevation Temperature
Strontium isotope ratios 87 Rb 87 Sr t 1/2 = 10 gy limestones young, low-Rb --------- . 700 . 705 . 710 87 Sr/86 Sr old, high Rb . 715 modern seawater
White, Price & Longstaffe: Anc. Mesoamerica 2007 seawater. 7092
Moon Pyramid, Teotihuacan, Mexico In use from AD 1 to 650: Sacrificial victims…from where?
Possible sources: δ 18 O and White, Price & Longstaffe, 2007 87 Sr/86 Sr
Teotihuacan
Conclusions Childhood residences of all the sacrificial victims at the Moon Pyramid were foreign to Teotihuacan and could be sourced to regions over Mesoamerica where Teotihuacanos are known to have exerted influence. White, Price & Longstaffe: Anc. Mesoamerica 2007
Forensics: The lady from Mammoth Lake
Hair was available for analysis Native American or Southeast. Asian?
HAIR SAMPLE Maize-rich diet
Mammoth native -14 tooth -12 -10 bone -8 -6 δ 18 O of water (SMOW, ‰) -4
DNA evidence: might be from a village in Oaxaca, Mexico
Local water --> HA Mammoth native -14 tooth -12 -10 Oaxaca village -8 bone -6 δ 18 O of water (SMOW, ‰) -4
This part of her history is still unclear! Victim’s bone? We need more rain data
Conclusions Potential isotopic records: birth childhood ? ? late adult life Isotopes can be used to trace trajectories of 1. Migration: O, C, N, Sr But not high specificity: 100’s - 1000’s km 2 Need “candidate sites”
Isotopes can be used to trace trajectories of 2. Diet: C, N isotopes: movement of hunters/gatherers coast<--->inland spread of cultigens 3. Climate: O, C in soils, animal bone + teeth drought seasonality temperature
Acknowledgements • • Tracy Prowse Phil Walker Martin Knyf Natural Sciences and Engineering Research Council of Canada (NSERC) • Social Sciences and Humanities Research Council of Canada (SSHRC)
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