BUTSER ANCIENT FARM ARCHIVE 1973-2007 Archivist Christine Shaw
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Provenance of Carbonised Seeds

The archaeological record abounds with carbonised material and seeds of both food plants and weeds form part of this record. The nature of the record means that the greatest part of the data come from settlement sites and so can only give a partial story, which is open to debate. Hence the availability of experimental results may be invaluable in resolving elements of the range of hypotheses advanced by various commentators.

An understanding of the many agricultural and construction processes likely to be involved in both the growth, harvesting, transfer and preparation for storage of both grain and straw is crucial to a proper understanding of how carbonised material may be generated in a particular location and how losses and changes in the community of seeds present at a given stage, place or time may be reflected in the final record.

Several elements of the work relating to this project have been touched on in the study of the Arable Plant Communities. The unavoidable interaction of some crop and field weed factors have been drawn out therein.

Some of the work carried out at the Farm has involved studies of the effects of different harvesting approaches on the transfer of field weed seeds through the agricultural production chain. Other work has incorporated features such as stubble burning and the burning of construction waste, such as straw found to be unsuitable for thatching.

About 1990, Dr Peter Reynolds published an extensive paper on his first 10 years work on this topic. The paper contains more than just some crucial experimental work on the generation of carbonised seed in fires, especially those fires based on the disposal of waste straw, which might arise from harvesting for the grain yield but, it is argued, more likely from the provision of thatching straw. There are known records of finds of carbonised seeds in settlement areas divorced from obvious activities, such as cooking, and for which no ready explanation has ever been advanced before this paper was published.

The paper first analyses what is known about ancient harvesting methodology and how various methods might relate to both grain recovery and to the impact on the availability of straw as a product and its suitability for a range of uses such as thatch, fodder and bedding. Then some experiments are reported to support the arguments.

It is clearly demonstrated that straw intended for thatch, in particular, when imported to the settlement site, contains significant quantities of seed grains. There is also found to be clear contamination with a range of weed seeds. The relationship of these weeds to those existing in the fields is discussed., as they may provide an important "marker" in following the transfer of crops through various processes from harvesting onwards. Here there is an inter-relationship with the work at Butser on Arable Weed Communities.

There are some important results and discussions given for how best to generate straw suitable for thatching when hand cutting the ripe cereal stands in various ways. There is an incidental explanation offered for some of the paired post-holes frequently excavated on settlement sites. This relates to the formation of straw bundles for thatching.

The paper finally takes up the key theme of what happens when disposing of waste straw, from the thatching process, by the use of fire. It is a principal hypothesis that this is the origin of much if not all of the previously unexplained carbonised seed "scattered" around settlement sites.

Reference:

"Zur herkunft verkohlter Getreidekoerner in urgeschichtlichen Siedlungen : eine alternative Erklaerung" (Eng. trans. "On the origin of carbonised cereal grain in prehistoric settlements : an alternative interpretation"), Reynolds P J, in Archaeophysica 13, "7000 Jahre bauerliche Landschaft : Entstehung, Erforschung, Erhaltung (Eng.trans. 7000 years of rural landscape : origin, research, conservation ) 1992


Additional material is given in a much wider ranging paper which gives some overlapping discussion of the material in the German paper but in shortened form, on pp 404-406, as it predates the experimental work referred to above, which originated from this earlier thinking.

"Carbonised seed, crop yield, weed infestation and harvesting techniques of the Iron Age", Reynolds P J, Les techniques de conservation des grains a long terme" 1985 3.1 397-403 CNRS Paris.