How do we know about Roman food? – waterlogged plant remains
Archaeologists learn about Roman food from a range of sources; mosaics, wall paintings, artefacts, written evidence, and bioarchaeological remains of foodstuffs. Plant foods, such as fruits, spices, cereal grains and pulses, are found at archaeological sites due to four types of preservation. These are charring, desiccation, calcium-phosphate mineralisation and waterlogging (see the glossary).
Waterlogged plant remains have provided archaeologists with some of the best evidence for plant foods in the north-western Roman Empire, showing that a wide range of new herbs, fruits and nuts were adopted. When plant remains are discarded into permanently wet places, they do not decay as they would on the ground surface or in compost bins. Waterlogged conditions are referred to as anaerobic, meaning there is no oxygen present. Bacteria, which would usually decay plant tissue, need oxygen to survive – without this, a wide range of plant remains can survive for thousands of years. These include ‘delicate’ remains such as celery seeds, box leaves, straw and bracken. Plant remains like this very rarely survive by charring (carbonisation).
Waterlogged conditions are found at 2 types of archaeological sites:
- Places which have been constantly waterlogged, forever. This happens due to a combination of settlements being built next to water, such as Roman London and York, frequent rainfall (Britain!), and the disposal of organic rubbish (stable flooring, food waste) faster than it can decay. This creates waterlogged conditions on the ground surface, and a wide range of organic materials are preserved, including floor timbers, leather shoes, and plant foods. A great example is the waterlogged conditions in the Walbrook Valley, London, where recent excavations by MoLA have uncovered timber drains.
- The bottoms of many wells, which were dug to provide water in Roman times, have remained below the water table for the last two millennia. This means Roman settlements on dry land, such as Silchester, can still produce waterlogged plant remains from wells. The cramped, dark and wet conditions of wells are tricky to excavate, but a range of evidence for food waste, fodder material and settlement vegetation can be recovered.
Samples of sediment taken from wells are processed using a flotation tank to extract the plant remains. Plant remains usually float on the surface of water, and can be collected in a sieve with a mesh size of 0.25mm.
The ‘waterlogged flot’ from samples is then taken back to the lab and sorted under a microscope. Seeds and other plant remains like leaves, buds, cereal chaff and fruit stones are removed, and identified by comparing them to seeds in a modern reference collection. This is a lengthy process, but the results can tell us about the fruits and flavourings consumed by different communities who lived within the Roman Empire. We can also learn how diets change over time, and even how they varied between households!
For more information about waterlogged plant remains:
- Integrated Archaeobotanical Resource (University of Sheffield online tutorial)
- MOLA Walbrook Discovery Programme blog (waterlogged timbers, baskets, plant remains and more from excavations in central London)