By Hannah

In a research school dedicated mainly to studying rocks and the environment, I like to think studying human remains is a bit of a novelty. I am part of the Archaeogeochemistry group, (introduced a few weeks ago by Kelsie), who work on using scientific methods for archaeological research.

My research focuses on using stable isotopes, mainly oxygen (δ18O) and strontium (87Sr/86Sr), in human teeth to answer questions about past human migrations and ancient diets **

The kind of people I like working with
The kind of people I like working with.

By measuring isotopes in human teeth we can roughly identify the geographical or geological location of the food an individual was consuming during the time the teeth were forming. This sounds like witchcraft I know, but it’s true! Let me explain.

Oxygen isotopes differ in rain, due to the temperature and the amount of rain in a particular region which creates this beautiful geographical distribution. Oxygen in all it’s isotopic forms, is incorporated in all human tissues as carbonates, phosphates, hydroxls etc.

Global values of oxygen isotopes (δ18O) in precipitation (Figure from waterisotopes.org, Bowen 2015)
Global values of oxygen isotopes (δ18O) in precipitation (Figure from waterisotopes.org, Bowen 2015).

Strontium isotopes differ in bedrock, due to the age and composition of the rock which becomes the bioavailable strontium in the plants and animals of that area. Strontium then substitutes in the place of calcium in human tissues.

Map fo France showing strontium (87Sr/86Sr) values (IRHUM database, Willmes 2015)
Map fo France showing strontium (87Sr/86Sr) values (IRHUM database, Willmes 2015).

The oxygen and strontium isotopes in the food you consume are worked into the teeth and as teeth are not remodelled throughout life, the childhood values are retained into adulthood.

By looking at modern maps, like those shown above, we can compare the values in human tissues to those predicted in that region. Matching values indicate an individual has either not migrated or lived in an area with the similar values in childhood. If values don’t match then perhaps the individual has migrated and that’s where it gets exciting.

Like many other scientific methods though, isotope analysis does not give us definites, rather a variety of possibilities. By interpreting this data alongside archaeological, historical and cultural evidence, isotope analysis can help fill in the blanks and shine light on archaeological questions which were pretty hard to answer previously.

In most archaeological settings people would have had little chance to eat non-local food, but in a modern age where the majority of your supermarket options are foreign, our isotopic signatures are getting messy. So to assist future archaeologists please eat local produce and drink local rainwater, that way you will have a local isotopic signature and your geographic origin will be identifiable!

** When I mention ancient diets, people often assume I am talking about identifying the Paleo Diet, that diet craze which basically promotes eating like a caveman. My work has nothing to do with the Paleo Diet, but I have ranted about the Paleo Diet to the Archaeogeochem kids over coffee, my major issue with it being the archaeological inaccuracies, nerdy I know.

The diet is based on what is believed to be the diet of humans during the Palaeolithic time period. This gigantic time period encompasses the first appearance of modern human ancestors, the evolution of homo sapiens and then the development and expansion of modern humans.

My issues are:

  • Human diets (and humans themselves) would have changed during this time period. Identifying the diet of past populations is not straight forward and identifying particular resources is sometimes as hard as milking a bull.
  • Available resources would differ across the globe, do you pick a particular region and eat only foods available in that region, or do you cheat and eat like a Palaeolithic global traveller?
  • Modern domesticated plants and animals differ from their Palaeolithic versions, after years of selective breeding. Take Brassica oleracea, a native species to coastal southern and western Europe, which has been selectively bred to become cabbage, kale, cauliflower, broccoli, kohlrabi, brussel sprouts and broccolini.

Animals have also gone extinct both during and after the Palaeolithic, which would have been utilised by modern humans and their ancestors. If you were hungry enough you would probably eat most of the animals which went extinct during this time period, see the link below for recipe ideas. (Quaternary extinctions; animals once available for eating)

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