History of Ireland 400–800

The early medieval history of Ireland, often called Early Christian Ireland, spans the 5th to 8th centuries, from the gradual emergence out of the protohistoric period (Ogham inscriptions in Primitive Irish, mentions in Greco-Roman ethnography) to the beginning of the Viking Age. The period notably includes the Hiberno-Scottish mission of Christianised Ireland to regions of pagan Britain and the spread of Irish cultural influence to Continental Europe.

At the start of the period, Ireland had emerged from a mysterious decline that archaeological evidence suggests had hit population levels and standards of living from c. 100–300 CE, called the Irish Dark Age by Thomas Charles-Edwards. The population was entirely rural and dispersed, with small ringforts the largest centres of human occupation. Some 40,000 of these are known, while there may have been as many as 50,000, and "archaeologists are agreed that the vast bulk of them are the farm enclosures of the well-to-do of early medieval Ireland". Souterrains, underground passages and chambers for hiding in or escaping through, are common. It is likely that raiding Great Britain for slaves and other loot gave an important boost to an otherwise almost entirely agricultural economy. The lakeside enclosures called crannógs continued to be used and seem especially associated with crafts.

The older view that early medieval Irish farming concentrated on livestock has been overturned by pollen studies and other evidence, and it is now clear that cereal farming was increasingly important from about AD 200 onwards, with barley and oats more important crops than rye, wheat and others. Cattle were greatly prized, and cattle-raiding constituted a large part of warfare, so that cattle needed the constant presence of a herdsman in daylight hours and were put in an enclosure at night. By the end of the period the largest herds were probably those of monasteries. Generally mild Irish winters seem to have meant they were never put in roofed shelters in winter, although young calves might spend a period in the house. There was very considerable clearance of forests in the early part of the period, such that by the 9th century, large tracts of forest appear to have been rare, and the native Scots pine cleared almost to extinction; the large areas of bogland were harder for the medieval Irish to affect.

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