Saturday, 28 February 2015

How Science Works - European History

Bouldnor Cliff submerged pre-historic site
DNA recovered from underwater British site may rewrite history of farming in Europe | Science/AAAS | News

An interesting example of how science works appeared in Science a couple of days ago. It concerns DNA evidence that domestic wheat, normally associated with farming, was being used by hunter-gatherers living in what is now southern England 8000 years ago, 2000 years before agriculture is believed to have reached north-west Europe.

Rather annoyingly, the article quotes archaeobotanist Dorian Fuller, of University College London, who was not involved in the research, as saying "[The work confronts archaeologists] with the challenge of fitting this into our worldview". Now, I'm not entirely sure what a 'worldview' is exactly but I suspect it's some sort of post-modernist nonsensical construction implying that all sorts of views of the world are possible and even equally valid, but reading the article it's very clear that what might need to be adjusted is this 'worldview' itself because this particular 'worldview' is a conclusion based on evidence. There is no fitting of new facts into a pre-existing conclusion; just the opposite in fact. The conclusion is adjusted to allow for the new information, just as the title of the article itself implies.

I just wish scientists would be a little less careless in the way they express themselves because creationist quote-miners looking for something to take out of context to mislead their target market with, will seize on phrases like that with glee and claim it shows science is as dogmatic as religion and has sacred conclusions that can't be changed, so scientists 'fit the facts into a preconceived world view', therefore it is no more valid than is Intelligent Design creationism and even looks like an attempt to mislead people. I suspect the problem is that scientists generally assume they are talking to an honest, educated audience and not one looking for something with which to mislead scientifically illiterate people with no real interest in the truth.

Any way, with that rant out of the way, let's look at the findings and how they may require us to change our minds when weighed against other evidence - exactly what science does.

A team of plant geneticists led by Robin Allaby, a plant geneticist from the University of Warwick, UK examined the sediment from a recently discovered submerged neolithic site 11 metres below the surface at Bouldnor Cliff, Isle of Wight, just off the South Coast of England. This sediment has been dated by various means to about 8000 years before the present. They were looking for evidence for the spread of domestic plants into Britain but what they found was surprising. In addition to the unsurprising evidence for oak trees, herbaceous plants, etc, they also found DNA evidence of two types of domestic wheat which originated in the Middle East and which does not grow wild in northern Europe.

The Mesolithic-to-Neolithic transition marked the time when a hunter-gatherer economy gave way to agriculture, coinciding with rising sea levels. Bouldnor Cliff, is a submarine archaeological site off the Isle of Wight in the United Kingdom that has a well-preserved Mesolithic paleosol dated to 8000 years before the present. We analyzed a core obtained from sealed sediments, combining evidence from microgeomorphology and microfossils with sedimentary ancient DNA (sedaDNA) analyses to reconstruct floral and faunal changes during the occupation of this site, before it was submerged. In agreement with palynological analyses, the sedaDNA sequences suggest a mixed habitat of oak forest and herbaceous plants. However, they also provide evidence of wheat 2000 years earlier than mainland Britain and 400 years earlier than proximate European sites. These results suggest that sophisticated social networks linked the Neolithic front in southern Europe to the Mesolithic peoples of northern Europe.

Oliver Smith, Garry Momber, Richard Bates, Paul Garwood, Simon Fitch, Mark Pallen, Vincent Gaffney, and Robin G. Allaby;
Sedimentary DNA from a submerged site reveals wheat in the British Isles 8000 years ago;
Science 27 February 2015: 347 (6225), 998-1001. [DOI:10.1126/science.1261278]

Incidentally, this submarine site was discovered quite by chance when a lobster was seen throwing Stone Age tools from its burrow.

So, what we have now is DNA evidence that wheat was present in Southern England about 8000 years before the present when previous opinion was that it had just about reached the Balkans and the area we now call Hungary by then and was brought into Britain when agriculture spread north-westwards across Europe, reaching Britain about 2000 years later. The lack of wheat pollen in the sediment is strongly indicative that the wheat wasn't grown locally, but was acquired by trade or some other means from farmers from much further east.

But hunter-gatherers indulging in long-distance trade is also something of a problem. What surplus goods did they trade with? Having something to exchange implies being able to produce more than just enough to live on and this implies either agriculture or manufacture which in turn implies a settle existence and control of natural resources.

The other possibility is some natural resource, such as good quality flint or well-made stone tools, of course. There is evidence that they made wooden boats so they had the means to trade up the European rivers like the Rhine and Seine or maybe into the Baltic Sea and it would have been within their means to portage boats between the Rhine and the Danube and so travel down to the Black Sea to the agricultural areas. And of course they might not even have had to make a long journey like that. There could have been a trading network with goods travelling east and wheat traveling west. It doesn't need ancient Britons themselves to travel all the way to Romania and the Don valley, only to cross the English Channel or exchange good with those who crossed in the other direction, for domestic wheat to end up in Britain.

A counter-argument comes from Peter Rowley-Conwy, an archaeologist at the Durham University, UK:

The authors do not do justice to the chronology of the spread of agriculture... [T]housands of directly radiocarbon-dated cereal grains [argue against farming in Western Europe that early]. One DNA study of this kind is just not enough to overturn all this.

But then it's possible that low-level wheat production as agriculture spread slowly, might not have left enough cereal grains to have been discovered, yet. There is evidence from Germany that agriculturists and hunter-gatherers co-existed and even used the same cave in which to bury their dead for some 800 years so it's entirely possible that they could have co-existed in southern Britain.

In the immediate post-glacial period, as trees moved back into Britain before sea-levels rose and cut the islands off from the rest of Europe, flooding the occupied site at Bouldnor Cliff in the process, it is generally accepted that the weather was much wetter, so the lowlands would have been heavy wet clay and heavily wooded - ideal for hunter-gatherers - so the best land for agriculture would have been the tops of the chalk hills. The shallow soil would actually have suited primitive ploughs. So we could have had a period where a few hill farmers occupied the chalk downs while hunter-gatherers lived in the wooded lowlands and river valleys.

Quite simply, there is not enough evidence yet to say conclusively that agriculture spread more quickly than we thought and had reached southern Britain by 8000 years ago, but this new DNA evidence at least raises that possibility. What science does now is to weigh that evidence against contrary evidence while geologists think of what sort of evidence would decide the matter and where to look for it. Meanwhile the pros and cons will be voiced, articles written and conferences addressed, always in a spirit of respectful scepticism and open-mindedness, and eventually a new consensus will be reached when enough evidence has been found on which to base opinions. This can only happen in a discipline free from sacred dogmas where the possibility of being wrong is always acknowledged, doubt is a valuable commodity and nothing is ever known with absolute, unchallengeable certainty.

This is the very antithesis of fitting the new evidence into a world view; it is actually adjusting a worldview to accommodate new evidence. I wonder when was the last time that the loons at the Discovery Institute, or people like Ken Ham and Ray Comfort, had the intellectual integrity or moral courage to change their minds to accommodate new evidence. Which religious fraud can ever afford to admit to doubt and uncertainty or the possibility of changing his mind? Ask any creationists what evidence would change their mind, or what evidence they would accept accept as proof of evolution and they'll usually refuse to answer or will admit that there is nothing. Ask any scientist what would change their mind and they will usually be able to spell out exactly what would do it.

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