During the Neolithic period, starting about 6,000 years ago, the first people living in Ireland whose ancestors had hunted and gathered along the coastlines of Erris from about 9,000 years ago, began to cut down the forestry to clear land for growing crops and grazing livestock. Because the underlying rock type was ancient and heavily weathered schists the soil was thin and easily eroded by inclement weather. After a couple of years the crops began to fail and the Neolithic people had to clear the native woodlands further and further inland to clear more land for their crops. With minor changes in climate and high rainfall levels the land became blanketed by the bog and remains that way to the current day. When present-day turf cutters harvest the bog for fuel, archaeological remains, mainly from the Neolithic and early Bronze Age, which have become buried under the bog often come to light. Some archaeological sites are marked on Ordnance Survey maps.