Strontium Isotopes and Bones

16 November 2008

Interview with

Jane Evans

stonehengeJane - What we've done is use strontium isotopes which can trace the effect of soil composition on your diet to look at ancient migration patterns in humans and animals.

Ben - Why is it that you can use strontium and the different isotopes available to actually find out where things have come from?

Jane - Strontium basically comes from the rocks. From the rocks it gets into the plants and into the food chain. The advantage of strontium is that it's basically linked to the age of the underlying rocks. In Britain we have a huge diversity of rocks of different ages and these all tend to give a different strontium isotope signal to the overlying biosphere. We can pick this up and make use of it.

Ben - Specifically you've been using strontium isotope analysis for archaeological purposes. Whereabouts were you based?

Jane - Well we've done a lot of the work in and around Stonehenge and one of the great advantages of the Stonehenge area is it's based on chalk: the chalky downs. The chalk has a very distinctive isotope signature. It gives us a chance to be quite clear as to who and what has been raised on the chalk and who that we found buried in the chalk had to have come from somewhere else.

Ben - What have you been able to see?

Jane - Right, well. In looking at human beings that have been buried at Stonehenge we've found, for instance that Bronze Age Boscombe bowmen who are in a grave near Stonehenge have clearly come from an area that's well away from Stonehenge and they all move during their childhood. We've got the first definitive evidence of human migration from the human remains as opposed to extrapolating this from the artefacts that people find in the graves.

Ben - Strontium isotope analysis is so powerful that you can actually plot how people have moved throughout the course of their life.

Jane - Throughout their childhood one of the restrictions for humans - not perhaps for animals - is that their teeth form in childhood. Since it's the tooth enamel that we use we are restricted to looking at where people were during their childhood. That in its own right can be quite interesting.

Ben - Can you do the same sort of thing?

Jane - With animals their teeth form in a slightly different way and, particularly with grazing animals their teeth are forming through to the animal's maturity. You can actually track the history of the animals grazing into a later period of its life relative to a human. Some of these animals that we've looked at do appear to have grazed in areas quite distant from the chalk where their remains are found.

Ben - What do you think this says about the area where their remains were found? Was there something special that attracted people and their animals?

Jane - I think there are a number of things. I think the interesting thing about the animals first is they're not all local. First we can immediately say we're not dealing with small local feast. Neither are we dealing with a place where people come from far away but animals and meat are supplied by local suppliers. We're looking at a local situation where people are bringing animals from quite distant places and quite disparate places to this site. By that very observation it appears of significance and importance. Durrington Walls itself is a huge site. It must be that it has some meaning for these people.  These people from different parts of Britain are communicating and contacting each other and drawn by the same set of principles and desires to come to this place.

Ben - So a technique of geological origin by looking at the strontium isotopes and rocks. Also not only to use those as an extra tool for archaeology but also to learn something about our social history.

Jane - Yes. I find that the very attractive side of this. You can go from a bunch of bones to Neolithic communication.

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