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.

Origins 5 – Domesticated Bliss

Happy February, readers! I hope you’re not too wet.

Now, I was lucky enough to receive as a Christmas present this excellent volume:

Cunliffe, B. (2012). Britain Begins (Oxford University Press; Oxford).

The prolific and erudite knight Professor Sir Barry Cunliffe probably needs no introduction for the readership of this blog but, for the curious, here’s a link to his departmental page, and to his rather more up-to-date Wikipedia entry.

So, this is a great book, as well-written and scholarly as you’d expect, with splendid production values (lots of maps and photographs, full colour throughout). It tells the story of Britain and Ireland between 10,000 BC and AD 1100. The book sets itself up as the successor to the ages-long tradition of ‘origins myths’ – the latest answer to the general question, Where do we come from?

“Like the myth-makers of the distant past, we are creating stories about our origins and ancestors conditioned by the world in which we live.” (p.vii)

With this in mind, there’s some fascinating introductory, historiographical matter about the stories that have been told about British origins throughout history, from ancient Greek allusions, all the way through to cutting-edge DNA research.

So, from a Farming Unearthed point-of-view, what’s inspired me to blog about this book?

Well, oddly enough, it ain’t agriculture. At least, not as we know it. I’m only up to the Mesolithic so far, in Chapter 4. The Neolithic, with all its new-fangled farming technologies, awaits me in Chapter 5. So, with this in mind, what do we make of the Mesolithic site at Oakhanger in the Weald with its unusually high percentages of hazel and ivy pollen? The interpretations cited by Cunliffe are thought-provoking (p.109):

“…there may have been deliberate felling of other trees such as alder, lime, and oak around the camp to allow hazel to flower  more freely and thus to produce a greater yield of hazel-nuts…”

“…one suggestion is that ivy was collected and brought to the periphery of the camp as fodder to attract deer during the winter months [i.e. to hunt them], when food was in short supply…”

Now, while it would perhaps be playing semantic games to call these practices “agriculture”, nonetheless to my mind this is something rather more than hunting-gathering: it seems like a kind of environmental management, to enhance local access to wild foods. I suppose the difference is that the productive environment isn’t being entirely managed by human hands. The encouragement of hazel growth isn’t quite arboriculture; but if you started planting and nurturing hazel saplings in your own specially-grown plants, would that count? And, crucially, how could we identify such a subtle difference in the archaeological record?

One archaeological clue, at least for some species, in at least some circumstances, is domestication. The emergence of domesticated varieties, distinct from their wild progenitors, implies that “environmental management” had passed a tipping point, that human intervention had effectively disrupted the process of natural selection: domestic traits are those which offer little or no advantage in the wild, but are selectively favoured (consciously or otherwise) by farming.

Here’s a nice example: the shattering and non-shattering of wheats. Put simply, wild wheats shatter; domesticated wheats don’t shatter. That is to say: wild wheats have a brittle rachis, which allows spikelets to disarticulate spontaneously, thus shattering the reproductive units (grains) over the ground and helping the plants to reproduce themselves; barbs on the spikelets help them to stick in the ground, and to deter hungry animals, to increase chances of germination. Domesticated varieties, by contrast, don’t shatter: the spikelets stay put, all the better for harvesting by hand.

So, a simple indicator of the division between “gathering” and “farming”?

Well, no, as it happens, because you could sow and harvest a shattering variety of wheat, just so long as you harvest the spikelets before they start spontaneously disarticulating. It would not be a domesticated crop, in this case, but it would be a cultivated crop: an important distinction, and one central to the debate about when and how agriculture began.

But that’s another story.

Some references:

Cappers, RTJ & Neef, R (2012). Handbook of Plant Palaeoecology (Barkhuis, Groningen): pp.380-387.

Renfrew, C & Bahn, P (2012). Archaeology: Theory, Methods and Practice (6th ed., Thames & Hudson, London):pp.273-292.

Tanno, K-I & Willcox, G (2006). “How fast was wild wheat domesticated?”, Science 311 (no.5769): p.1886.

Origins 4 – Of Mustard and Manure

It’s always a pleasure when agricultural archaeology and related disciplines hit the headlines, and it’s happened at least twice recently. BBC News has courteously flagged up two pieces of new research, indicating the hitherto unexpected sophisication of farming and diet in prehistory.

This very day, we learn that “Prehistoric Europeans spiced up their cooking.” And, better yet, the original research article is open access so you can see it for yourself – see the link below for Saul et al. 2013. The results are from ‘The Baltic Foragers and Early Farmers Ceramic Research Project’, in which Mesolithic and Neolithic pottery from modern Denmark and northern Germany were examined for food residues. Now, I’d heard of lipid residue analysis before, but in this case the evidence comes from phytoliths preserved in charred residues on the pottery. Literally, phytolith translates as something like ‘plant-stone’: they are the remains of an insoluble silica that gets deposited amongst cells in the living plant, and survives even once the plant itself has been burned away. Usefully for us, they can often be identified to family, genus or even species level, allowing us some insight into plant use and ecology (see Cappers & Neef 2012 p.130 for a good brief summary). In this case, the phytoliths point to Alliaria petiolata (M. Bieb) Cavara & Grande – more commonly known as garlic mustard. The context suggests culinary use; the plant gives a strong taste but has negligible nutritional value; hence, those prehistoric chaps and chapesses were apparently spicing their food, simply for the delectable taste. Yum.

And why not, after all? Why shouldn’t hunter-gatherers and early farmers have been concerned to eat something tastier than hulled wheat, hazelnuts and crab apples? For me, though, this raises the question of gathering vs. cultivation – i.e. were they deliberately growing spices, in a kind of herb garden set-up? This might sound fanciful for the Neolithic but, again, if you can invent agriculture, why not herb gardens?

And talking of Neolithic inventiveness, here’s the second piece of news that interested me: “Neolithic farmers used manure on crops.” This one strikes rather closer to home, not just because it came shortly after Dung Awareness Day, but because the work was led by my colleagues, elders and betters at Oxford University. The School of Archaeology even issued its own press release. Neolithic plant remains from across Europe were subjected to stable isotope analysis, and the results indicate that certain crops were manured – a means of fertilisation whose usage wasn’t previously known as early as this.

The ‘certain crops’ bit is highly significant, since it implies that the Neolithic farmers were selecting those crops that they thought would benefit the most from manuring, leaving the hardier types to fend for themselves. The lead researcher Dr Amy Bogaard, quoting to the BBC, draws out the wider significance of these findings:

“These results point to a different kind of farming where they were making fixed investments in land that they intended to hang onto and pass on to future generations…”

This is cutting-edge stuff, and excitingly we can expect more good things to come, because Dr Bogaard is running an impressive ERC-funded four-year project investigating “The Agricultural Origins of Urban Civilization”, which now has its own website and blog that are well worth keeping an eye on. (Incidentally, they’ve got a remarkably similar header picture to my new one…).

The paper has now been published – it’s one of those where the number of authors exceeds the number of pages, demonstrating the wealth of expertise behind these results: Bogaard et al. 2013.

So, the moral of the story – if any – is that you should never underestimate prehistoric farmers.

MJM.

Bibiliography

Bogaard, A., Fraser, R., Heaton, T.H.E. et al. (2013). ‘Crop manuring and intensive land management by Europe’s first farmers’, Proceedings of the Natural Academy of Sciences 110 (31), pp.12589-12594.

Cappers, R.T.J. & Neef, R. (2012). Handbook of Plant Palaeoecology, Groningen/Barkhuis.

Saul H, Madella M, Fischer A, Glykou A, Hartz S, et al. (2013). ‘Phytoliths in Pottery Reveal the Use of Spice in European Prehistoric Cuisine’, PLoS ONE 8(8): e70583. doi:10.1371/journal.pone.0070583