 From about 4500 BC , Neolithic settlers arrived introducing cereal cultivars , a housing culture ( similar to those of the same period in Scotland ) and stone monuments . A more advanced agriculture was to develop . At the Céide Fields , preserved beneath a blanket of peat in present @-@ day County Mayo , is an extensive field system , arguably the oldest in the world , dating from not long after this period . Consisting of small divisions separated by dry @-@ stone walls , the fields were farmed for several centuries between 3500 BC and 3000 BC . Wheat and barley were the principal crops imported from the Iberian Peninsula . 
 From about 4500 BC , Neolithic settlers arrived introducing cereal cultivars , a housing culture ( similar to those of the same period in Scotland ) and stone monuments . A more advanced agriculture was to develop . At the Céide Fields , preserved beneath a blanket of peat in present @-@ day County Mayo , <a href='drop_aux' title='1'><mark>is</mark></a>an extensive field system , arguably the oldest in the world , dating from not long after this period . Consisting of small divisions separated by dry @-@ stone walls , the fields <a href='uninflect' title='2'><mark>were</mark></a> farmed for several centuries between 3500 BC and 3000 BC . Wheat and barley <a href='uninflect' title='3'><mark>were</mark></a> the principal crops imported from the Iberian Peninsula . 
From bout 4500 cos , Neolithic settlers arrived introducing cereal cultivars , a housing culture ( similar to those of da same period in Scotland ) and stone monuments . A more advanced agriculture was to develop . At tdaCéide Fields , preserved beneath a blanket of peat in present @-@ day County Mayo , an extensive field system , arguably thdaldest in thedarld , dating from not long after this period . Consisting of small divisions separated by dry @-@ stone walls , the fields was farmed for several centuries between 3500cusC and 300bcuzBC . Wheat and barley was the principal crops imported from the darian Peninsula .