Radiogenic Isotope Geochemistry IV Lecture 39. U & Th Decay Series Isotopes continued.
Stable and radiogenic isotopes in Archaeology and Anthropology
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Transcript of Stable and radiogenic isotopes in Archaeology and Anthropology
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Stable and radiogenic isotopes
in Archaeology and
Anthropology Henry P. Schwarcz
McMaster UniversityHamilton, Ontario, Canada
Christine White and Fred Longstaffe
University of Western OntarioLondon, Ontario, Canada
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Definitions (loose!)
Anthropology: How people live (“culture”)
Archaeology: How people Lived (prehistoryand later)
Paleoanthropology: Who “people” were (evolution)
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The samples: Bones, teeth
Time depth: 3 My to recent
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Bone is a composite material consisting of: 60 wt% hydroxyapatite: HA
Ca5(PO4, CO3 ) 3 (OH, CO3)
OXYGEN
+ 40% collagen (protein) N, C ATOMS
CARBON
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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
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Stable isotopes can help inform:
Paleodiet: “you are what you eat + x ‰”
Paleoclimate: rain, drought, cold, heat
Migration: where did people come from?
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0 10 20 30 40 50 60 70
years
M1
M2, P1, etc
M3
teeth
bones
hair, etc.
death
Stages of life recorded
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PALEODIET
Nutrient molecules:
protein: C, N, H, O
Fat: C, H, O
Carbohydrate: C, H, O
δ13C, δ15N, δ18O of each nutrient varies depending on the source
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0
5
10
15
20
25
-35 -30 -25 -20 -15 -10 -5
13C (l ) (PDB)
15N
(l
) (A
IR)
HERBIVORES
C3 PLANTS
CARNIVORES
C4 PLANTS
MARINE CARNIVORES
MARINE HERBIVORES
C4PLANTS
δ1
5N
(‰
) (
AIR
)
δ13C (‰) (PDB)
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IsotopicAnalysis
δ13C(bone collagen) = δ13C (food*) + 5‰
[* mainly dietary protein (?)]
δ13C (CO3-apatite) ≈ δ13C (food) + 11 ‰
δ15N (collagen) = δ15N(diet) + 3 ‰[“trophic level effect”]
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You are here
Marine consumers: how far would you go for sushi?
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Walker and DeNiro Am. J. Phys Anth., 1986
Conclusion: Everyone was eating seal meat, but more in the islands
Seal
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MALIBU site
Los Angeles
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6
8
10
12
14
16
18
20
22
-22 -20 -18 -16 -14 -12 -10
Female
Male
Linear(Male)Linear(Female)
Walker & DeNiro
Same trend as on Channel Islands: females have higher trophic level
Schwarcz & Walker, in prep.
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Travelling foods: Maize arrives in Ontario ~ AD 700
Maize from Mexico
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After AD 700 maize replaced wild carbohydrates…
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Paleoclimate
Isotopes as indicators of
Temperature: paleotemperaturesMollusk shells in middens Speleothems Teeth, bones
Humidity, Rainfall δ13C C3 vs C4 plants (wet vs dry) δ15N in collagen: rainfall (aridity) δ18O cycles in tooth enamel:
seasonality of rain
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Paleoclimate
Isotopes as indicators of
Temperature: paleotemperaturesMollusk shells in middens Speleothems Teeth, bones
Humidity, Rainfall δ13C C3 vs C4 plants (wet vs dry) δ15N in collagen: rainfall (aridity) δ18O cycles in tooth enamel:
seasonality of rain
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δ18O Paleotemperatures: Sclerochronology
Isotopic cycles in marine shell carbonates Season of occupation of midden-sites
Matthieu et al., Paleo3,2005
Wintercollection
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Paleoclimate
Isotopes as indicators of
Temperature: paleotemperaturesMollusk shells in middens Speleothems Teeth, bones
Humidity, Rainfall δ13C C3 vs C4 plants (wet vs dry) δ15N in collagen: rainfall (aridity) δ18O cycles in tooth enamel:
seasonality of rain
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East Africa: calcite in soils
Levin et al., EPSL, 2004
C3,moist-------------------C4, hot,dry
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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)
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δ18O(bone)
δ18O(water)
δ18O bone tells us δ18O of local drinking water
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δ18O of meteoric water varies regionally
Decreases with
Increasing latitude (poleward)
Distance from sea (source of water vapor)
Elevation
Temperature
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Strontium isotope ratios
87Rb 87Sr t1/2 = 10 gy
.700 .705 .710 .715 87Sr/86Sr
limestonesyoung, low-Rb ------------------ old, high Rb
modern seawater
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White, Price & Longstaffe: Anc. Mesoamerica 2007
seawater .7092
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Moon Pyramid, Teotihuacan, Mexico
In use from AD 1 to 650: Sacrificial victims…from where?
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Possible sources: δ18O and 87Sr/86Sr
White, Price & Longstaffe, 2007
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Teotihuacan
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Conclusions
Childhood residences of all the sacrificial victims at the Moon Pyramidwere foreign to Teotihuacan and could be sourced to regions over Mesoamerica where Teotihuacanos areknown to have exerted influence.
White, Price & Longstaffe: Anc. Mesoamerica 2007
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Forensics: The lady from Mammoth Lake
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Native American or SoutheastAsian?
Hair was availablefor analysis
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HAIR SAMPLE
Maize-rich diet
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δ18O of water (SMOW, ‰)
-14 -12 -10 -8 -6 -4
Mammoth native tooth bone
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DNA evidence: might be from a village in Oaxaca, Mexico
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δ18O of water (SMOW, ‰)
-14 -12 -10 -8 -6 -4
Mammoth native tooth
Local water --> HA
Oaxaca village bone
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Victim’s bone?
This part of her history is still unclear!
We need more rain data
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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 km2
Need “candidate sites”
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Isotopes can be used to trace trajectories of
2.Diet: C, N isotopes: movement of hunters/gathererscoast<--->inland spread of cultigens
3. Climate: O, C in soils, animal bone +
teeth drought seasonality temperature
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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)