Sunday, January 25, 2015

Faint Traces, Grand Prospects?: Isotope Geochemistry and the Antiquities Trade

In the world of antiquities trade research, reporting and prosecution, especially where the seizure and repatriation of recently surfaced items is concerned, one of the most challenging tasks we all face is discerning whether or not what is stated about a piece (in documents or by suspects) is actually true, and known to be so at the time of sale or donation. The problematic legal loophole that a claim of purchase in "good faith" can represent, and the challenge often placed on claimant countries to meet the "burden of proof," instead of insisting that the defendant demonstrate that a contested item was not in fact looter or illegally exported; can make restitution challenging.

In an ideal world, the process of due diligence would always run smoothly. Every high-profile piece purchased by a museum, at auction, or online would automatically come with complete and independently verifiable documents attesting to legal export and import before the UNESCO convention, as well as before the passing of any State ownership legislation for the country in question.

Of course, the provenience, age, and archaeological culture stated in the paperwork would also match reality as determined by "subject matter expert" assessment. I don't need to tell you that the scenario above can at times be far off the mark. The very fact that the reality of the trade at all levels remains so messy is what keeps much illicit antiquities trade research, numerous federal investigations, and related calls for policy and legal reform, alive and well.

In this post, I'll provide some general background to what I think is a relatively overlooked and under-explored means to address some of these pressing cultural property concerns using the methods and tools of science! So let's start at the beginning. Forgive me for getting technical for a moment as I attempt to summarize the complex.

The Basics of Stable Isotopic Research

Every element on the periodic table has a variable number of 'isotopes' that differ in the number of neutrons in their atomic nuclei, but not the number of protons or electrons. Therefore, each separate isotope will have the same elemental properties, but slightly different atomic masses (deemed 'heavy' or 'light' based on neutron numbers).

For example, carbon has isotopes referred to as C12, C13, and C14. Numbers 12 and 13 are 'stable,' in that they always have the same mass and have never been known to decay. On the other hand, measuring the rate of decay of C14 against a known 'half-life' and relevant calibration curves gives us "carbon 14 dating." Isotopes that decay as a function of time are termed 'radiogenic.'

Although stable isotopes have consistent mass, they can vary in concentration ('abundance') across a geologic landscape, with altitude and latitude, through time, between species, or between materials. Measurements of variation in abundance ('fractionation') between what is sampled, and known or suspect naturally occurring background rates (primarily using IRMS: Isotope Ratio Mass Spectrometry) has opened a wide variety of new research avenues in many fields.

Geologists remain the main practitioners of isotope geochemistry, usually relying on the concentrations (not isotope ratios per se) of rarer 'trace elements' to drive new research on topics ranging from the origin and composition of meteorites, to planetary formation. However, since the 1980s or so, isotopes (especially carbon, oxygen, nitrogen, strontium; occasionally sulfur, calcium or barium) have seen exponentially increasing application to fields and diverse as palaeoclimatology, palaeontology, ecology, and my own human bioarchaeology.

In these fields, it is generally agreed that a 'multi-isotopic' approach can best serve attempts to reconstruct ecosystem trophic level, the complexities of diet, variation in water source, and migration across the lifespan of animals and humans both living and dead.

Whether one's topic is the impact of human activities on marine ecosystems over time using squid as a proxy measure, or my own postdoctoral research seeking to reconstruct changes in ancient human diet and community structure across various spatio-temporal contexts in the Near East and Mongolia; the goals are similar and the isotopes used are the same. Yet every day, labs around the world strive to push the frontiers of what's possible and devise new applications.

The Wide World of Applications

This brings us back to what I first set out to discuss; possibilities for stable isotopic research to inform antiquities trade questions. Can it be done? Is there precedent? Yes, there is! As a means to clarify a most-likely region of origin and simultaneously indicate that something might not in fact derive from where it's said to, stable isotopes are revealing their potential in numerous 'applied' contexts.

From tracking poaching patterns (here and here), investigating suspicious food origins (here or here), tracing illicit drug shipments (here and here) and even forensic homicide investigations, their use continues to grow. Even within archaeology, the analysis of food residues from ceramics is a hot topic.

And yet, work that utilizes isotopes (primarily oxygen and strontium) to understand how an artifact's raw material source does or does not correlate with known or suspected archaeological provenience and any dealer or museum records that may exist; such work is still in its infancy. Any artifact with an organic component to it (shell, bone, wood, fiber, hair, you name it) is fair game.

So, why isn't this done all the time, you might ask? A couple of caveats do need to be mentioned, such as the need to destroy an albeit tiny amount of the artifact in question, and thus the need for permission to sample and keep good records. Furthermore, all such investigations must be cognizant of the fact that a multi-component artifact with unknown origins can not be fully investigated by sampling just one component.

To develop the full potential of isotopic research within the antiquities trade arena, criminological and legal expectations will need to be matched to the reality of what the science can provide at the moment through as many different test-cases as possible. This is no quick-fix or palliative. I've wondered in the past if there are too many variables, but it's my opinion that it just hasn't been looked at hard enough.

Sneak Preview

I personally remain convinced of the untapped potential, despite the trial and error that will be required. Is it not worth it to add every tool possible to the global fight against the trade? This post is the first of what I hope to be a short series exploring this possibility in more detail via hypothetical scenarios, as well as sharing details of an actual project that myself and a few colleagues currently have in pilot stage and are working to take further.

In the meantime, for those of you also on Twitter, I am pleased to announce that you can now follow a brand new Twitter feed I've created. @FaintTraces is dedicated specifically to news, views, job postings, etc. pertaining to bioarchaeology, isotopic approaches to archaeological science, and applications to cultural heritage questions. This is in addition to my usual @DamienHuffer.

For now, my own labwork continues apace with the data starting to come in. Skeletal sampling also marches forward, nearing its end, and I am gearing up for a busy Spring. As I continue to prepare for conferences in February and April, various talks, and the quest for continued employment (beginning more or less now), I look forward to once again sharing my musings on this and other exiting topics.