Origins 7 – The Ghost of the Sea

Max Planck (1858-1947) was a trailblazer of quantum theory, that confusing branch of physics which describes the inherent unpredictability of the very small. It’s kind of appropriate, then, that researchers at his namesake foundations – two of the Max Planck Institutes in Germany – are shedding uncertainty in the tiny world of molecular archaeology.

It’s a response to what was, arguably, last year’s blockbuster story in agricultural archaeology: the identification of 8,000-year-old wheat DNA in sediments at Bouldnor Cliff, at the bottom of the Solent. Farming Unearthed covered the story here. The shocker, as I wrote then, is that this makes the wheat Mesolithic – 2,000 years older than the first evidence for farming in Neolithic Britain. It was suggested on this basis that early farmers from further east were bringing their wheat products to Britain long before cultivation reached these shores – an idea which would have paradigm-quivering implications for agricultural prehistory in north-western Europe.

It sounded so improbable, and there were sceptical responses from the start, but the argument also seemed very strong. The team seemed to have done everything possible to avoid contamination, prove the integrity of their samples, and demonstrate that they’ve really got wheat DNA.

But, it’s now being argued, they may have missed something. Bouldnor, we have a problem.

Geneticists from the afore-mentioned Max Planck Institutes (for Development Biology and Evolutionary Anthropology) have applied rigorous tests to investigate the antiquity of the sedimentary ancient DNA, or ‘sedaDNA’.  I confess that I can’t follow all the arguments and statistics of Weiß et al. 2015. But the crux of it seems to be about deterioration. Ancient DNA, even if it’s good enough to identify, still doesn’t look like new DNA. It doesn’t even look like recent historic DNA. Essentially, ancient DNA has a distinctive pattern of reasonable wear and tear, fraying at the edges: damage, whereby cytosine starts to look like thymine at the ends of the molecules, known as ‘C-to-T substitution’.

The teams conducted thorough statistical comparisons between the Bouldnor Cliff sedaDNA and other libraries of well-dated ancient and modern DNA, and conclude that the pattern of C-to-T substitution at Bouldnor doesn’t look anywhere near 8,000 years old. Apparently, it looks even more modern than material collected 85-170 years ago (Weiß et al. 2015, p.3).

Now, like I say, most of the details of this research are beyond my ken. Way over my head. But the essential clash of results between the two research projects is deeply confusing. The original research appeared to rule out all conceivable means of contamination: the sediments were collected in stainless steel boxes straight out of sealed Mesolithic contexts deep under the Solent, and analysed in pristine labs that hadn’t handled wheat before. Not only that, but the type of wheat – where identifiable – is described as ‘domesticated einkorn wheat… Near Eastern wheat, as distinct from distantly related species in northern Europe and Britain’ (Gaffney et al. 2015, pp.25-6). Einkorn, one of the earliest domesticated cereals, hasn’t been popular in Britain for thousands of years. It was old news when Boudicca was a lass. It still exists today, to be sure, but why – of all possible modern contaminants – should einkorn turn up here?

einkorn-589213_1280

Einkorn – a golden oldie (source)

Einkorn, forsooth!

Any cultivated plant DNA in a Mesolithic context would seem implausible, but a Near Eastern strain matching einkorn is arguably the least implausible of the bunch. At least there’s a hypothesis – albeit a rather earth-shattering one – to explain how it might have got there. But if it’s actually less than 200 years old, how do we explain that?

Its presence is surprising if it’s ancient, but also pretty mind-boggling if it’s modern. Am I missing something? Could the state of being buried under the seabed somehow inhibit molecular spoilage?

One thing’s for certain: we haven’t yet heard the last of this mysterious story.

MJM.

*****

You’ll be pleased to know that the new research is in an open-access article:

Weiß, C.L., Dannemann, M., Prüfer, K. & Burbano, H.A. (2015). “Contesting the presence of wheat in the British Isles 8,000 years ago by assessing ancient DNA authenticity from low-coverage data”, eLife 4, http://dx.doi.org/10.7554/eLife.10005
The original work is discussed by:
Gaffney, V., Garwood, P. & Momber, G. “How sedimentary DNA brought wheat to mesolithic Bouldnor Cliff”, British Archaeology no.142 (May/June 2015), pp.22-27
And the first, seminal article can now be accessed with free registration to Science:
Smith, O., Momber, G. et al. (2015). “Sedimentary DNA from a submerged site reveals wheat in the British Isles 8000 years ago”, Science 347, pp.998-1001.
Advertisements

One thought on “Origins 7 – The Ghost of the Sea

  1. I am uberbaffled. For a start, I’m surprised that there could be mesolithic people at a high enough population density to be worth exporting wheat to. What would they trade in return? Furs, pelts, slaves, …..?

    But the other possibility is also odd: whence einkorn recently? Hm, a couple of hundred year old. Hm. Napoleon, it has to be to do with Napoleon. Could his mad sortie to Egypt …. ah, could any of the returning Royal Navy ships have brought back einkorn? Aha! The RN evacuated the trapped French Army, as a deal for the French surrendering rather than the British having to keep fighting them, or occupying Egypt.. So you’d stock the transports with food (including einkorn?????) for the captives and crew. Was einkorn on sale in Egypt at the time?

    Then, when the French have been dropped off and the transport ships return to Blighty, someone says “We can get rid off this filthy Gyppo wheat now”, and over the side into the Solent it goes. Never mind transport ships; the same could apply to ships-of-the-line, frigates, and whatnot.

    So there you have it. How to test that hypothesis?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s