Using Science to Discover the Crops of the Past

How do we know about what crops were grown in the past? We use a variety of different scientific techniques to investigate old methods of arable farming and the crops that were grown before we started making detailed records.

Crop remains survive at archaeological sites as a result of three main preservation methods; waterlogging (where complete immersion in water protects the plant material from exposure to oxygen, and therefore restricts decay), carbonisation (where burning converts the organic material into carbon, which is inert and therefore does not decay) and dessication (where the absence of moisture means that organic material does not break down fully). A range of different recovery techniques are used to extract these plant remains from archaeological deposits.

These remains are then identified in a laboratory, using a reference collection. The reference collection includes modern plant material that can be directly compared with the samples from the archaeological sites, to ensure that the identification is correct.

Once classified in this manner, the plant material is quantified. Sometimes this means counting every seed, or portion of the seed) and sometimes it means weighing the crop remains. Quantification means that the results can be subjected to statistical analyses and tests, to investigate the relative importance of each crop type in different areas and at different times during the past. Sometimes the weeds and other plant remains also give us information about how crops were managed in the past. For example, some weed seeds could indicate that a crop rotation system was used, or that the fields were irrigated.

Information about what crops were used, where, when and how can provide fascinating insights into how our agricultural systems of today emerged. As food crops are an important aspect of diet in many societies, this information is also interesting for anyone who wants to know about important food stuffs that were relied upon as different societies emerged, grew and declined in the past.