Contents During the last glacial period, and up until about 12,000 years ago, most of Ireland was periodically covered in ice. For the part of the United Kingdom, see Northern Ireland. This theory proposes that the Celticisation of Ireland may have been the culmination of a long process of social and economic interaction between Ireland, Britain and adjacent parts of Continental Europe. A land of green fields for crop cultivation and cattle rearing limits the space available for the establishment of native wild species. Ireland once dominated the world s market for whiskey, producing 90% of the world s whiskey at the start of the 20th century. Members of the government are chosen from both the Dáil and the upper house of parliament, the Seanad.
The largest denomination is Roman Catholicism representing over 73% for the island (and about 87% of the Republic of Ireland). There is continued debate over the missions of Palladius and Patrick, but the consensus is that they both took place  and that the older druid tradition collapsed in the face of the new religion. These occasionally bring destructive winds and higher total rainfall to these areas, as well as sometimes snow and hail. The population soared in the latter part of this century and the architectural legacy of Georgian Ireland was built. The introduction of the potato in the second half of the 16th century heavily influenced cuisine thereafter. These missions brought written language to an illiterate population of Europe during the Dark Ages that followed the fall of Rome, earning Ireland the sobriquet, the island of saints and scholars.
A near complete conquest was achieved by the turn of the 17th century, following the Nine Years War and the Flight of the Earls.  Irish is also taught in mainstream English-speaking schools as a compulsory subject, but has been criticised for its ineffectiveness.  The earliest evidence of human presence in Ireland is dated at 10,500 BC, demonstrated by a butchered bear bone found in a cave in County Clare.. English rule of law was reinforced and expanded in Ireland during the latter part of the 16th century, leading to the Tudor conquest of Ireland. The situation in Northern Ireland is complicated by the issue of private companies not supplying Northern Ireland Electricity (NIE) with enough power. .