Thursday, March 12, 2015

Wheat in an Ancient World

Editor's Note

An analysis published in the journal eLIFE in November questioned the authenticity of the 8,000 year-old wheat DNA found in the British Isles, cited below. This criticism could overturn the results of Allabay et al.'s study. Alternatively, Allaby et al.'s conclusions, if verified, could drastically change our understanding of the spread of agriculture to the British Isles. This critical review of results is a normal part of the scientific process, so we encourage you to keep up-to-date on the situation and draw your own conclusions. 



Fig.1. Domesticated einkorn wheat (Triticum monococcum subsp. monococcum), like these plants in Turkey, may have arrived in the British Isles 2,000 years earlier than expected. (Credit; Mark Nesbitt, 2006)

The application of scientific collections is not just limited to natural or physical sciences. With the advent of newer technologies, the field of archaeology has been able to support material evidence with precise chemical, dating, and DNA analyses. Sediment cores - which can date back to 55 million years ago - are particularly useful for understanding a prehistoric settlement. As materials fall to the ocean floor, they stack on top of past sediments and ultimately form a chronology of the life and environment of that location.

Underwater mystery

Although many core analyses focus on recreating the climate conditions of a particular time period, University of Warwick researcher Robin Allaby and his colleagues took sediment cores for a cultural and human migration study off the southern coast of England. Their analysis of Bouldnor Cliff, a prehistoric Mesolithic settlement submerged under eleven meters of ocean water, recently appeared in the journal Science and may rewrite a part of British history.

The team of archaeologists with the universities of Warwick, Bradford, and Birmingham found evidence of einkorn wheat (Triticum monococcum subsp. monococcum) at the Mesolithic site -- a plant which was among the first to be domesticated and cultivated in history. They also used radiocarbon dating to place the now underwater settlement at around 8,000 years ago. This find contradicted the widely held belief that farming and crop species reached the British Isles only 6,000 years ago, after spreading from central Europe and ancient Anatolia in modern day Turkey.



Fig.2. The site called Bouldner Cliff is underwater and just off the coast of the Isle of Wight (pictured) in Great Britain. (Credit: Barbara M├╝rdter, 2005)

 

Dating a cultural shift

So how does a domesticated plant reach Great Britain 2,000 years before farmers began cultivating cereal grains? The answer lies in further analyses done by Allaby and his team. Although they found evidence of einkorn at the site, they found no plant pollen or farming tools that would place a crop field at Bouldnor Cliff. They concluded that the site was populated by hunter-gatherers who were likely involved in a larger network of trade with mainland Europe. Trade (or warfare) could easily contribute to the spread of materials, food, plants, and ideas among late Mesolithic groups. 

In addition to tracking possible human migration through the evidence of agriculture, this study also shows a cultural shift. The pre-agricultural Mesolithic Period gave way to the Neolithic Period, signified by development in human technology and the rise of farming. The settlement found by Allaby et al. probably did not farm, but they were involved in a much wider network of communities than previously thought. Further analyses of sediment cores from other Mesolithic settlements and early Neolithic sites could inform this debate on the movement of people 8,000 years ago as well as the entrance of agriculture into western Europe.



References:

Schiermeier, Q. (2015, February 26). Ancient DNA reveals how wheat came to prehistoric Britain. Nature News. Retrieved from http://www.nature.com/news/ancient-dna-reveals-how-wheat-came-to-prehistoric-britain-1.17010.

Smith, O., Momber, G., Bates, R., Garwood, P., Fitch, S., Pallen, M., Gaffney, V., & Allaby, R.G. (2015, February 27). Sedimentary DNA from a submerged site reveals wheat in the British Isles 8000 years ago. Science, 347 (6225): 998-1001. DOI: 10.1126/science.1261278.




Glossary

sediment cores
Cylindrical section of sediment collected by drilling into the ocean floor with a drill. As material falls to the ocean floor, it forms layers which allow scientists to create a chronology going back millions of years.
Mesolithic [Period] (Middle Stone Age)
Ancient cultural period between the Paleolithic Period (Old Stone Age) and Neolithic Period (New Stone Age). Also called the Epipaleolithic, it is generally dated from 20,000 BP to 10,500 BP in modern day Turkey and the Middle East and 10,000 to 5,000 BC in northwestern Europe
radiocarbon dating
Dating matter which was once living (plant or animal material) through measuring radioactive decay.
Neolithic (New Stone Age)
Period of development in human culture between 10,200 BC in parts of the Middle East to the 4,500 and 2,000 BC, seen by the development of farming, plant and animal domestication, and the use of pottery (although not always the case)

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