The earliest settlers arrived around 7,000 BC in the Mesolithic or middle stone-age period. They arrived in the north across the narrow strait form Britain. These people were mainly hunters.
Colonists of the Neolithic, or new stone age, period reached Ireland around3,000 BC. These were farmers who raised animals and cultivated the soil. Many remnants of their civilization – houses, potter, and implements – have been excavated at Lough Gur in Co. Limerick and some can be seen at the folk park now developed around the lakeside site. The Neolithic colonists were largely self-sufficient but engaged in a limited form of trading in products such as axe-heads.
Many of their religious monuments have survived, the most impressive of which is the great megalithic tomb at Newgrange in Co. Meath.
Prospectors and metalworkers arrived about 2,000 BC. Metal deposits were discovered and soon bronze and gold objects were being manufactured. Many artifacts made by these bronze-age people have been found, among them axe-heads, pottery and jewelry. About1,200 BC another movement of people reached Ireland, producing an even greater variety of weapons and artifacts. A common type of dwelling in use at this time was the crannog, an artificial island, with palisades on all sides, constructed in the middle of a lake.
The people who made the greatest impact on Ireland were the Celts. The earliest waves of Celtic invaders may have reached the country from central Europe as early as the 6th century BC with subsequent groups arriving up to the time of Christ. The Celts belonged linguistically to the great Indo-European family. They soon came to dominate Ireland and the earlier settlers
The Celtic culture of the La Tčne civilization – named after a Celtic site in Switzerland – reached Ireland around the 2nd century BC.
Celtic Ireland was not unified politically, only by culture and language. The country was divided into about 150 miniature kingdoms, each called a tuath. A minor king ruled a tuath, subject to a more powerful king who ruled a group of tuatha, who was in turn subject to one of the five provincial kings. This political situation was very fluid, with constant shifts in power among the most important contenders.
Celtic Ireland had a simple agrarian economy. No coins wee used and the unit of exchange was the cow. People lived on individual farms and there were no towns. Society was rigidly stratified into classes and was regulated by the Brehon Laws, an elaborate code of legislation based largely on the concepts of the tuath as the political unit and the fine, or extended family, as the social unit.