stable and radiogenic isotopes in archaeology and anthropology henry p. schwarcz mcmaster university...
DESCRIPTION
The samples: Bones, teeth Time depth: 3 My to recentTRANSCRIPT
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
Definitions (loose!)
Anthropology: How people live (“culture”)
Archaeology: How people Lived (prehistoryand 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
Ca5(PO4, CO3 ) 3 (OH, CO3)
OXYGEN+ 40% collagen (protein) N, C ATOMS
CARBON
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 ‰”
Paleoclimate: rain, drought, cold, heat
Migration: where did people come from?
0 10 20 30 40 50 60 70
years
M1M2, P1, etc
M3teeth
boneshair, etc.
death
Stages of life recorded
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
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
δ15
N (
‰)
(AIR
)
δ13C (‰) (PDB)
IsotopicAnalysis
δ13C(bone collagen) = δ13C (food*) + 5‰
[* mainly dietary protein (?)]
δ13C (CO3-apatite) ≈ δ13C (food) + 11 ‰
δ15N (collagen) = δ15N(diet) + 3 ‰[“trophic level effect”]
You are here
Marine consumers: how far would you go for sushi?
Walker and DeNiro Am. J. Phys Anth., 1986
Conclusion: Everyone was eating seal meat, but more in the islands
Seal
MALIBU site
Los Angeles
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.
Travelling foods: Maize arrives in Ontario ~ AD 700
Maize from Mexico
After AD 700 maize replaced wild carbohydrates…
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
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
δ18O Paleotemperatures: Sclerochronology
Isotopic cycles in marine shell carbonates Season of occupation of midden-sites
Matthieu et al., Paleo3,2005
Wintercollection
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
East Africa: calcite in soils
Levin et al., EPSL, 2004
C3,moist-------------------C4, hot,dry
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)
δ18O(bone)
δ18O(water)
δ18O bone tells us δ18O of local drinking water
δ18O of meteoric water varies regionallyDecreases with
Increasing latitude (poleward)
Distance from sea (source of water vapor)
Elevation
Temperature
Strontium isotope ratios87Rb 87Sr t1/2 = 10 gy
.700 .705 .710 .715 87Sr/86Sr
limestonesyoung, low-Rb ------------------ old, high Rb
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: δ18O and 87Sr/86Sr
White, Price & Longstaffe, 2007
Teotihuacan
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
Forensics: The lady from Mammoth Lake
Native American or SoutheastAsian?
Hair was availablefor analysis
HAIR SAMPLE
Maize-rich diet
δ18O of water (SMOW, ‰)
-14 -12 -10 -8 -6 -4
Mammoth native tooth bone
DNA evidence: might be from a village in Oaxaca, Mexico
δ18O of water (SMOW, ‰)
-14 -12 -10 -8 -6 -4
Mammoth native tooth
Local water --> HA
Oaxaca village bone
Victim’s bone?
This part of her history is still unclear!
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 km2
Need “candidate sites”
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
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)