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Stable and radiogenic isotopes in Archaeology and Anthropology

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Stable and radiogenic isotopes in Archaeology and Anthropology. Henry P. Schwarcz McMaster University Hamilton, Ontario, Canada Christine White and Fred Longstaffe University of Western Ontario London, Ontario, Canada. Definitions (loose!)

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Presentation Transcript
slide1

Stable and radiogenic isotopes in

Archaeology and Anthropology

Henry P. Schwarcz

McMaster University

Hamilton, Ontario, Canada

Christine White and

Fred Longstaffe

University of Western Ontario

London, Ontario, Canada

slide2

Definitions (loose!)

Anthropology: How people live (“culture”)

Archaeology: How people Lived (prehistory

and later)

Paleoanthropology: Who “people” were

(evolution)

slide3

The samples: Bones, teeth

Time depth: 3 My to recent

slide4

Bone is a composite material

consisting of:

60 wt% hydroxyapatite: HA

Ca5(PO4, CO3 ) 3 (OH, CO3)

OXYGEN

CARBON

+ 40% collagen (protein)

N, C ATOMS

slide5

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

slide6

Stable isotopes can help inform:

Paleodiet: “you are what you eat + x ‰”

Migration: where did people come from?

Paleoclimate: rain, drought, cold, heat

slide7

Stages of life recorded

M1

teeth

M2, P1, etc

M3

bones

hair, etc.

death

0 10 20 30 40 50 60 70

years

slide8

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

slide9

δ15N (‰) (AIR)

C4

PLANTS

δ13C (‰) (PDB)

slide10

IsotopicAnalysis

δ13C(bone collagen) = δ13C (food*) + 5‰

[* mainly dietary protein (?)]

δ13C (CO3-apatite) ≈δ13C (food) + 11 ‰

δ15N (collagen) = δ15N(diet) + 3 ‰

[“trophic level effect”]

slide12

Walker and DeNiro Am. J. Phys Anth., 1986

Seal

Conclusion: Everyone was eating seal meat, but more in the islands

slide13

Los Angeles

MALIBU site

slide14

Schwarcz & Walker, in prep.

Walker & DeNiro

Same trend as on Channel Islands:

females have higher trophic level

slide17

Paleoclimate

Isotopes as indicators of

Temperature: paleotemperatures

Mollusk 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

slide18

Paleoclimate

Isotopes as indicators of

Temperature: paleotemperatures

Mollusk 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

slide19

δ18O Paleotemperatures: Sclerochronology

Isotopic cycles in marine shell carbonates 

Season of occupation of midden-sites

Winter

collection

Matthieu et al., Paleo3,2005

slide20

Paleoclimate

Isotopes as indicators of

Temperature: paleotemperatures

Mollusk 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

slide21

East Africa: calcite in soils

C3,moist-------------------C4, hot,dry

Levin et al., EPSL, 2004

slide22

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)

slide24

δ18O of meteoric water varies regionally

Decreases with

Increasing latitude (poleward)

Distance from sea (source of water vapor)

Elevation

Temperature

slide27

Strontium isotope ratios

87Rb  87Sr t1/2 = 10 gy

limestones

young, low-Rb ------------------ old, high Rb

.700 .705 .710 .715

87Sr/86Sr

modern seawater

slide29

Moon Pyramid, Teotihuacan, Mexico

In use from AD 1 to 650: Sacrificial victims…from where?

slide30

Possible sources: δ18O and 87Sr/86Sr

White, Price & Longstaffe, 2007

slide32

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

slide34

Hair was available

for analysis

Native American or SoutheastAsian?

slide35

HAIR SAMPLE

Maize-rich diet

slide36

Mammoth

native

tooth

bone

-14 -12 -10 -8 -6 -4

δ18O of water (SMOW, ‰)

slide38

Local water --> HA

Mammoth

native

Oaxaca village

tooth

bone

-14 -12 -10 -8 -6 -4

δ18O of water (SMOW, ‰)

slide39

This part of her history is still unclear!

Victim’s bone?

We need more rain data

slide40

Conclusions

  • Potential isotopic records:
  • birth  childhood ?? late adult life
  • Isotopes can be used to trace trajectories of
    • Migration: O, C, N, Sr
    • But not high specificity: 100’s - 1000’s km2
    • Need “candidate sites”
slide41

Isotopes can be used to trace trajectories of

  • 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
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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