After a long pause, the blog is back – and it’s a blog of surprises. These particular surprises reached my attention through both British Archaeology magazine and the online news pages of Science. For those of you lucky enough to have full-blown access to Science, the reference is this:
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.
Admirable clarity in that title, snappily stating the two things that had me so surprised – or “gobsmacked”, as they said in the Mesolithic.
Surprise 1 – sedimentary DNA
Bouldnor Cliff is a Mesolithic hunter-gatherer site with a twist: it’s underwater, 11m deep in the Solent, off the coast of the Isle of Wight. Although under threat of disturbance from modern shipping and fishing activity, it’s still remarkable for its surviving organic remains, including Britain’s oldest known piece of string (over 8,000 years old). The inundation of the site, when the Solent grew to separate the Isle of Wight from the mainland, has helped to preserve remarkable remains such as this, which have been investigated by maritime archaeologists since 1999: see what the folk at the Maritime Archaeology Trust have to say. But in this latest study, it’s not artefacts that are causing a stir: it’s aDNA in the sediment. Yes, they’re sequencing aDNA (= “ancient DNA”) left in the sediment by plants that have long since decayed. I had no idea that this was possible. Received wisdom (among non-geneticists, at least) seems to be that extracting and sequencing aDNA from any biological remains is fiendish enough, let alone from traces left in the sediment. But they’ve done it, and convincingly too, with unexpected results.
Surprise 2 – wheat?!
Yes, wheat. Besides the trees and wild grasses that you’d expect in a Mesolithic landscape, the team also identified domesticated wheat DNA in the sediment.The deposits were sealed on the seabed, and modern contamination has been ruled out: wheat seems, quite genuinely, to have been present at this hunter-gatherer site, circa 6,000 BC. And, to be blunt, it shouldn’t be there.
That is to say, it jars with the accepted narrative. Cast your mind – or your browser – back to a previous post in this series: “Britain goes nutty”. This reviewed an article by archaeobotanists Stevens & Fuller, who looked at the dated evidence for crop remains in prehistoric Britain. In accord with the conventional narrative, they found that domesticated crop remains appear in the archaeological record pretty soon after 4,000 BC. So the Bouldnor wheat DNA is 2,000 years older than we might expect. It predates the introduction of agriculture to the British Isles in the Neolithic period. So what’s going on here?
Well, Gaffney and co. stress that this new evidence doesn’t mean that we should redate the British Neolithic. Just as one swallow doesn’t make a summer, one site with wheat DNA in the sediment doesn’t make an agricultural dawn. Things would be different if we had securely-dated pollen – a stronger indicator of local cultivation – but the DNA could easily represent something imported from faraway lands. That in itself would be of huge significance, implying far-reaching networks linking British Mesolithic hunter-gatherers with new-fangled Neolithic farmers further east, long before farming communities became established in northwestern Europe.
With evidence like this, the cultural picture of this period could become a lot more complex, along with our understanding of the dynamics of early agriculture and its spread across Eurasia. Heady stuff, but for now I’ll leave you with the image of those Bouldnor hunter-gatherers, peering curiously at an object newly arrived on their shores: “Congratulations! You are the lucky winner of a Luxury Wheat Gift Hamper from the Fertile Crescent Company. Try before you sow! Call now to reserve your free Neolithic Package while stocks last…”
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.