There is evidence of human settlement near the Fens from Mesolithic times. Particularly along the fen edges and on the low islands within the fens, to take advantage of the hunting and fishing opportunities of the wetlands. The Fens would have provided them with food, fuel, building materials and summer grazing for their animals. The most well known Bronze Age site is at Flag Fen in Peterborough where an entire wooden causeway has been excavated. Must Farm nearby is rapidly becoming as well known and is revealing significant and important artifacts.
Roman farming and engineering
The Romans constructed the Fen Causeway across the Fens to link what later became East Anglia with central England; it runs between Denver and Peterborough. They also linked Cambridge and Ely, but generally their road system avoided the Fens except for minor roads designed for exporting the products of the region, especially salt, beef and leather. Sheep were probably raised on the higher ground of the Townlands and fen islands. The Roman period also possibly saw some drainage efforts, including the Car Dyke along the western edge of the Fenland between Peterborough and Lincolnshire, but most canals were constructed for transportation.
Early post-Roman settlements
These settlements were made on the Townlands. It is clear that there was some prosperity there, particularly where rivers permitted access to the upland beyond the fen. Such places were Wisbech, Spalding, Swineshead and Boston. All the Townlands parishes were laid out as elongated strips, to provide access to the products of fen, marsh and sea. On the fen edge, parishes are similarly elongated to provide access to both upland and fen.
The Dark Ages and Middle Ages
After the end of Roman Britain, there is a break in written records. It is thought some of the Iceni may have moved west into the Fens to avoid the Angles, who were migrating across the North Sea from Angeln (modern Schleswig) and settling what would become East Anglia. Surrounded by water and marshes, the Fens provided a safe area that was easily defended and not particularly desirable to invading Anglo-Saxons.
When written records resume in Anglo-Saxon England, the names of a number of peoples of the Fens are recorded in the Tribal Hidage and Christian histories. They include North Gyrwe (Peterborough and Crowland), South Gyrwe (Ely), the Spalda (Spalding), and Bilmingas (part of south Lincolnshire).
In the early Christian period of Anglo-Saxon England, a number of Christians sought the isolation of the wilderness that the Fens had become. These saints, often with close royal links, include Guthlac, Etheldreda, Pega, and Wendreda. Hermitages on the islands became centres of communities which later became monasteries with massive estates.
Monastic life was disrupted by Danish raids and settlement, but was revived in the mid-10th century. In the 11th century the whole area was incorporated into a united Anglo-Saxon England. It remained a place of refuge and intrigue. It was here that Alfred Aetheling was brought to be murdered and here where Hereward the Wake based his insurgency against Norman England.
Fenland monastic houses include the so-called Fen Five (Ely Cathedral Priory, Thorney Abbey, Croyland Abbey, Ramsey Abbey and Peterborough Abbey) as well as Spalding Abbey. As major landowners, the monasteries played a significant part in the early efforts at drainage of the Fens.
During most of the twelfth century and the early thirteenth century, the south Lincolnshire fens were afforested. The area was enclosed by a line from Spalding, along the River Welland to Market Deeping, then along the Car Dyke to Dowsby and across the fens to the Welland. It was deforested in the early thirteenth century.