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News from the Nerd Herd back in Aberdeen

July 26, 2014

With the blog jam-packed with the daily updates, wonderful archaeology and (miraculously) blue skies of another field season, I thought I’d post a long-overdue update on all-things-isotope.

At Nunalleq, we’ve been using a method called stable isotope analysis to investigate the archaeological foodweb and subsistence patterns during the occupation of the site. This technique involves the chemical analysis of preserved animal and human biological materials, providing direct evidence of diet. As those of you reading this blog will have gathered, the preservation conditions at Nunalleq are incredible, with the site not only yielding animal bones, but also leather, animal fur, claw, and even cut strands of human hair. These materials are an invaluable archive of stable isotope data!

From 2010, I’ve been working on both human hair and animal remains at the site. Our first data from Nunalleq, focusing on some of the first phases of the site, revealed a very mixed terrestrial-marine diet – in interesting contrast to earlier sites in Western Alaska and the Alaska Peninsula. This year I’ve been focusing on the more recent phases of the site. Given the long period of site use, the large collections of human hair from Nunalleq will allow us to look at diet through time, and to see if and how the Little Ice Age influenced the foodweb and subsistence menu at the site.

Stable isotope analysis utilises mass spectrometry, an analytical chemistry technique. However, ahead of mass spectrometry, samples have to be prepared and cleaned – a very time consuming process, whether you are dealing with bone or hair/fur. Earlier this summer, I had some company in the lab – high school work experience student, Alice Jaspars. Alice, an aspiring archaeological scientist, helped prepare a batch of hair samples from the most recent phases of the site ready for analysis – a process that involves stripping the hair of debris and lipids (grease) using chemicals (chloroform and methanol) and an ultrasonic bath.

A long lock of hair from one of the more recent phases of the site. The cut end is clearly visible, the evidence of hair cuts made long ago.

A long lock of hair from one of the more recent phases of the site. The cut end is clearly visible, the evidence of hair cuts made long ago.

As part of her work, she cleaned the long strand pictured here – one of around 6 or 7 strands we’ve found like this so far. When these long strands are found in the field, we geeks get especially excited! Human hair grows at a rate of ~1cm per month, which means a long section like this contains a dietary record that spans almost two years of an individual’s life. After Alice cleaned this particular sample, I was able to align the hairs and cut the lock into 5mm sections, which will provide bi-monthly isotope data. The tiny samples were then weighed out into small tin capsules, and are now waiting patiently to be analysed. I know the thrills of the lab cannot compare to those in the field, but when the Excel file with those data pings into my email inbox, I will be giddy!

As well as Alice, I’ve been lucky enough to be joined by two other wonderful isotope scientists on this project – PhD students Ellen McManus and Alex Jamieson. Ellen, a regular both on site and in the lab, has been primarily investigating isotopes in animal remains, in particular the dietary relationships between the inhabitants of Nunalleq and their canine companions. Uniquely, her work incorporates both zooarchaeological analysis and isotopes, and also promises to provide insights into the archaeological foodweb. Not only can this help us understand the subsistence menu at this site, but will also enable us to compare how animal ecology has changed in the area over the last few hundred years. Now in the dreaded final year of her PhD, Ellen is deeply ensconced in data analysis and writing, but I am really looking forward to seeing all her hard work come to fruition over the next months.

Alex is the newest member of our team, and making her way to Nunalleq as I write. Like Ellen, Alex will be focusing on animal remains to better understand the site, human subsistence choices and also animal ecology in deep time. Alex’s work, however, will focus on faunal mobility rather than diet – particularly the migratory behaviours of caribou, then and now. As tooth enamel grows incrementally, like the hair, we can sequentially-sample tooth enamel from animals we suspect may be migrants and analyse their strontium isotope ratios. These data correspond with the underlying geology the animal was living and feeding on at the time, allowing us to reconstruct the archaeological migration routes of this important subsistence species.

Well, I think that is more than enough isotopes for one day! I will check back in soon with updates on the DNA front too, but for now – back to the field season, incredible archaeology, and those hard-working diggers who make the isotopes possible!

Kate

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