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Jean M
11-04-2015, 10:54 AM
http://www.nature.com/news/ancient-dna-dispute-raises-questions-about-wheat-trade-in-prehistoric-britain-1.18702

Ancient DNA dispute raises questions about wheat trade in prehistoric Britain


Wheat DNA reported to be 8,000 years old lacks damage expected of its age, study contends.

An argument over the authenticity of ancient DNA is leading researchers to question a headline-making study which changed views on the dawn of farming in Western Europe.*

The study, published in Science in February 2015, reported finding of fragments of 8,000-year-old wheat DNA from soil in a prehistoric settlement submerged off the coast of England — thousands of years before the archaeological record suggests Neolithic farmers began cultivating cereal grains in Britain.

The discovery suggested that ancient Britons imported wheat, raising the possibility of trading networks that linked hunter–gatherers to farmers living as far away as the Balkans. “If the claim is right, they’re overturning the whole story of the colonization of Britain in the Middle Holocene. It’s a giant claim,” says Keith Bennett, a palaeoecologist at Queen’s University Belfast, UK.

But an analysis published on 3 November in eLIFE contends that the wheat DNA is too pristine to be 8,000 years old — because it lacks the biochemical-damage patterns that would be expected after so many millennia**. It more than likely represents accidental modern contamination, argues Hernán Burbano, an ancient-DNA researcher at the Max Planck Institute for Developmental Biology in Tübingen, Germany, who led the new work.


* Smith, O. et al. Science 347, 998–1001 (2015).
**Weiß, C., Dannemann, M., Prüfer, K. & Burbano, H., Contesting the presence of wheat in the British Isles 8,000 years ago by assessing ancient DNA authenticity from low-coverage data, eLIFE http://dx.doi.org/10.7554/eLife.10005 (2015).

alan
11-06-2015, 09:09 PM
thought that was likely. Basically mentally I dismissed this the minute I heard of it because it doesnt make any sense. 8000 years ago farming was nowhere near the isles.

Jean M
11-07-2015, 08:35 PM
thought that was likely. Basically mentally I dismissed this the minute I heard of it because it doesn't make any sense. 8000 years ago farming was nowhere near the isles.

My own view entirely. Delighted that this nonsense has been exposed so quickly.

parasar
11-10-2015, 03:44 AM
Nonsense?
Have the claims been retracted?

From the report it does not seem like it:
"DNA was submerged under cold water — conditions that, he says, led to its high level of preservation ...Allaby says that his team took extreme care in analysing sediment cores recovered at Bouldnor Cliff, an archaeological site submerged 11 metres underwater off the coast of England ... He notes that the wheat DNA had been maintained at 4 ºC since it became submerged roughly 7,900 years ago, which would improve DNA preservation. Using ancient DNA found in permafrost as a comparison, he estimates that just 5% of the cytosine bases would undergo deamination in these conditions. “This is really not detectable,” says Allaby, who plans to publish a formal response to the eLIFE paper soon."

So at best it is being disputed as the thread header noted.

Jean M
11-10-2015, 12:41 PM
Nonsense? Have the claims been retracted?

I have a great deal of respect for scientists who do retract previous astonishing claims with as much fanfare as they gave to them in the first place. Such people are more concerned about science than saving face. They don't want to lead people astray. Their urge is to correct a false impression as soon as possible, before it is perpetuated.

But not everyone does that. So the process of scientific enquiry does not depend on formal retractions. It depends on assessment by the body of scientists. A publication goes into print. It may have already gone through a limited process of peer review prior to print. But that is not the end of the process. It is then subject to review by any scientist who cares to read it.

This particular claim was unexpected and it was obvious that there could be alternative explanations than the one given. The obligation is not upon readers to believe every bizarre claim, but upon the people making it to prove it beyond all doubt. :biggrin1:

Megalophias
11-10-2015, 04:56 PM
A parallel case is "Naia", the 12 000+ year old remains of a Paleoamerican girl found underwater in a sinkhole in the Yucatan. She was determined to have mitochondrial haplogroup D1, but the results were later challenged because the purportedly ancient DNA didn't have the expected damage pattern. On the other hand, there was no evidence or clear source of contamination, so the authors stood by their work.

It's possible that DNA preserved under cold water decays differently than it does under ordinary conditions of burial. It is also possible that they are both contaminated. We may need more aDNA from these kind of settings to find out.