stable and radiogenic isotopes in archaeology and anthropology henry p. schwarcz mcmaster university...

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)