The Roman Empire not only unified the administration, language, religion and culture of the peoples concerned, but also influenced eating habits for many centuries. In a study published in the journal Environmental Archeology, four researchers traced the ethnobotanical history of sweet chestnut (Castanea sativa) and walnut (Juglans regia). Thus, for the first time, a comprehensive picture of the early distribution and cultivation history of these tree species in Western and Central Europe emerged.
An ethnobotanical story
The sweet chestnut and the walnut are cultivated trees. There is evidence that people were cultivating them as early as the first millennium BC. The study now shows what a decisive role the Roman colonial conquests played in the widespread spread of these two tree species in Central and Western Europe. This is particularly true for the chestnut, which experienced a real boom as a result of the Roman campaigns, especially on the southern slopes of the Alps and in France. The walnut was already widespread before that, which was consolidated by the Roman colonisation.
Ancient texts testify that the Romans, like the Greeks, cultivated the chestnut primarily because of its rapid growth and its durable wood. With the walnut tree, on the other hand, wood and food production were balanced from the beginning. With the planting of chestnut trees throughout Europe, the Roman Empire laid the foundation for the medieval chestnut culture. The sweet chestnut was used more and more as a food source and was at times also called the "bread of the poor", especially in southern Switzerland. Today, both tree species are economically important in Europe for wood and fruit.
Pollen and fruit leftovers give evidence of the distribution
By studying pollen (palynology) and plant remains from excavation layers, researchers can reconstruct the past distribution of plants. For this project, the team led by Patrik Krebs, a geographer at WSL, considered the region of maximum expansion of the Roman Empire. After a systematic analysis of data from the Neotoma Paleloecology Database, the researchers linked the entries to historical reports and archaeological excavation finds. They compared the conclusions drawn from this with scientific publications and other sources and thus drew the most accurate map of the distribution history of the sweet chestnut and the walnut to date.