Here's a novel way of identifying the erstwhile contents of an ancient pottery vessel: never mind the chemical composition of the residue, the lipids, the proteins, the isotope ratios, the pollen, the phytholiths, the seeds or the leaf fragments. Just scrape some gunk off the inside of the sherds and check it for DNA snippets to identify the organisms that produced it!
The beauty of this approach is that you will easily see if the DNA you've grabbed is likely to belong to the substance originally kept in the vessel. If you come up with your own DNA or that of a soil microbe or earthworm, then you know you've got it wrong. There's a book-length 1994 study by Biers et al. of perfume vials from classical antiquity where gas chromatography was used to identify the chemical composition of residues in the hope of matching perfume recipes preserved in written sources. This study was plagued by sample contamination: among the identified compounds, caffeine and nicotine made it clear that certain post-Columbian museum curators had been sloppy around their collections.
Anybody wanna buy a few amphorae of oregano-seasoned olive oil? It's just in from Crete. For you, my friend, special price.
[More blog entries about archaeology, dna, classical, mediterranean, archaeometry; arkeologi, dna, medelhavet, antiken, arkeometri.]
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I was a bit sad yesterday late afternoon. So I decided to go out into the forest, its the best cure. When I was in the darkest place a sparkle was gleaming in the last light of the sun, between the big trees, on a pine root. I went closer and there was a little bottle of glass. I took it in my hand and opened it with some awe, but it was only a nice smell of perfume coming out of it...:-) Then I saw the name on it "Spirit of Heaven".
What a beautiful experience!
I dunno know if this is a cure-all. Even if you find soil bacteria, there is no telling if it is modern contamination or ancient contamination. Sterile technique was not so thorough in the olden days.
Also, I presume that PCR amplification would be used. This technique has its own problems with contamination.
I wasn't suggesting seriously that it would be a cure-all. But you seem to misunderstand me: an amphora that's spent 2500 years on the seafloor or under two meters of stratification is very unlikely to have become contaminated with olive oil and oregano. You can see pretty easily if the stuff you're getting is at all plausible as original vessel content.
Oh good, my secret is safe.
Modern contamination could still be a problem too. There has been at least one instance of fish DNA found when studying an ancient mammal bone -- the fish DNA came from the oils in the plastic containers used to process the samples.
Contamination is just a fact of life with ancient DNA analyses. Problems arise when you can't be sure whether your data reflect the thing you're studying or just some irrelevant contamination. The case you mention, with fish DNA from a mammal bone, is a clear case and no big problem.
^^^
Oh, yes, it was obvious in that particular situation. But how would you know if someone was cooking fish in their pots or if it is contamination? That's the problem. It is possible to sort many such things out, but only if you know it is a problem first.
Well, no scientific method is ever fool proof, the best you can hope for is more methods, more studies, more analysis of contamination risks etc. I think this method could be really interesting as a complement to all the other incredibly vague and error-prone analyses we make of pottery. My only problem is how I will finally be able to prove cannibalism among Stone Age populations if all you do is shout modern contamination!? ^_^
Seriously though, combining DNA with lipids could bring some very interesting results. Now where can I buy my own pet scientist...? Ebay?
What's the exact reference for that Biers study?
thx
William R. Biers, Klaus O. Gerhardt & Rebecca A. Braniff. 1994. Lost scents : investigations of Corinthian "plastic" vases by gas chromatography-mass spectrometry. MASCA research papers in science and archaeology 11. Philadelphia.