Radiocarbon Dating Ancient Grease

20 years ago, radiocarbon dating was transformed by the widespread adoption of AMS analysis, accelerator mass spectroscopy. Willard Libby’s original scintillation-counting method demanded large sample sizes and a lot of time per sample. The sample size meant that many interesting things couldn’t be dated at all, and that once you had gotten a large enough chunk of organic material together, chances were that it would be heavily contaminated with later stuff. The time demands meant that prices were high.

Radiocarbon technology continues to advance. A few years back, I learned that a method had been perfected whereby cremated bone could be dated accurately. Hugely useful in Scandinavia where cremation was the rule for 2000 years until the introduction of Christianity. And now a paper (behind a pay wall) by R. Berstan et al. in the forthcoming issue of Antiquity describes a method to date lipids extracted from pottery! Ancient grease!

Neolithic scholars have been dating burnt food crusts from the surface of potsherds for years. Ideally, you find a characteristically decorated sherd with a lot of gunk on it, and then radiocarbon nails down a part of your pottery style chronology in calendar years. The problem is that most sherds with characteristic decoration have no food crust. But they do retain grease within their ceramic matrix. I expect this technique to become a big hit.

Update 11 September: Explains my buddy Ludvig Papmehl-Dufay,

“Cool stuff indeed. I haven’t read the paper, but I don’t think it’s such a big breakthrough: the same team (largely) published a similar study five years ago.

Stott, A. W., Berstan, R., Evershed, R. P., Bronk-Ramsay, C., Hedges, R. E. M. & Humm, M. J. 2003. Direct dating of archaeological pottery by compound-specific 14C analysis of preserved lipids. Analytical chemistry 2003:75, pp. 5037-5045.

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Comments

  1. #1 llewelly
    September 10, 2008

    What about glazed pottery? It seems to me the glassy surface would greatly reduce the amount of grease retained.

  2. #2 Martin R
    September 11, 2008

    Glazed pottery is a modern thing. Any stratification containing such pottery must be bulldozed away on sight, with extreme prejudice, to the hilt. It cannot be allowed to pollute our sites.

    Die, glazed pottery.

  3. #3 ArchAsa
    September 11, 2008

    Indeed, glazed pottery is a profanity. That said, there are some pretty old usages of glazing in the Mediterranean, but mostly only on the outside. You don’t waste expensive glazing where it is not seen.

    AMS-technology that helps us study even extremely small samples is the best thing to happen to archaeology since Libby first had his blessed realization. It’s a giant leap forward for prehistoric studies (which is all that really matters of course)

  4. #4 Martin R
    September 11, 2008

    I view modern society and science as a kind of substrate for our work. Most of what you see around you, most people in the world, are just sort of an operating system. And it’s running a single application: prehistoric archaeology.