You Are What You Eat

hamburger-headThe picture might be an exaggeration. The isotopes in your body aren’t!

The study of isotopes from the departments of chemistry and geology have, in recent decades, helped archaeologists and anthropologists alike answer questions. The answers most sought after when using isotope analysis are about past civilizations and there past diets, mobility, and trade. And can get further knowledge about past peoples and the environment they lived and culture.

Most people who think of isotope analysis think of absolute dating, which are radioactive isotopes ,like carbon-14, which decay in predictable “half-lives” to something more stable. This can be used, particularly C-14 in archaeology, to date certain items like artifacts, strata, and fossils. Absolute dating was actually used to determine the age of the Earth!

But few are familiar with “stable” isotopes. Which aren’t radioactive and so don’t go under radioactive decay over time. Because of this we can find artifacts and plants and animals skeletons with the same isotopic value from when they where alive. The most common elements used are Carbon(C-13), Nitrogen(N-15), Oxygen(O-18), and Strontium(Sr-87,Sr-86). These stable isotopes can then be used to study artifacts like ceramics, metals. soft tissue, bone, teeth, plants and soil. And the reason for the funny title is isotope values in organisms are a reflection of the there geographic location and diets. So, you literally are what you eat!

Types of Isotope Use

Isotopes to Study the Environment 

Learning about the past environments of past peoples can help explain the environmental factors they faced. Like agriculture, trade, and settled or nomadic lifestyles. An example would be people who lived in arid environments have enriched N-15 values while people who lived in mild environment have a low N-15 value.

Isotopes and Diet

This method provides a very direct approach to discovering the diets of past people and civilizations. Through the use of carbon and nitrogen isotopes it can determine terrestrial or marine consumption and the different plant life.

Isotopes to Study Mobility

Isotopes Strontium and oxygen can be used to study the travel of people, animals and artifacts like ceramics. can be used to study the trade among past civilizations and peoples migration from different geographical locations for they will have different isotopic values.

Examples in the Field

The Very English Eater

arrowpointboy20composite20sharpIn The Jamestown Rediscovery Project in 2005 they where able to discover a early inhabitant of the town near James Fort. From the bones he was a young European man that stood about 5ft 8in. And when they brought his remains to to Smithsonian Institution they did a isotopic analysis using C-13. This information can be valuable when studying colonial remains for they can help tell there original origins and how long they have stayed in America. Because maize have a richer source of C-13 compared to the other plant life in Europe which are barley, wheat, and rye. And over time as a colonial eats more local foods and plant life changing there nutrition that there body transports which changes over time there bones which reflect a diet with more C-13. But the Isotope analysis of the young man reflects that he had a low C-13 diet which reflects that he had no local food in his diet and that he most likely died shortly after arriving in Jamestown around 1607.

What did Egyptians Eat?   

Mummy of a Middle Class Egyptian Woman.

In Katheryn Emery’s blog Bones Don’t Lie she talks about the Diet of ancient Egyptians inferred from stable isotope systematics and whether depictions of Egyptian art really show how they lived. And based on the research gathered using human hair, enamel, and bones from a sample of 43 individuals from the Egyptian middle class. And based on the isotopic analysis using Strontium they consumed all local crops and meats. which makes sense since they where able to take advantage of the Nile river and delta. Which means they didn’t need to import food resources from other civilizations. Also based on the isotope analysis the article inferred that the Egyptian middle class had a ovo-lacto vegetarian diet. Which meant they primarily ate fruits and vegetables but also byproducts of animals like milk and cheese. Meat consumption was between 20% to a extreme of 50% of there diet. But this is still low compared to modern day where meat is around 65% of our diet. So they mostly kept to there greens.

Books and websites:

Written in Bone by Sally M. Walker – book about the excavation of Colonial James Town and Maryland. – Katheryn Emery’s blog – a good site about isotope analysis. Hopefully clears up anything that was confusing. I’m not the best at Chemistry.












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