Pollen analysis indicates that in the Mesolithic period of 8000 to 7000 BC The Burren looked completely different from today, with most of the uplands covered in a mixture of deciduous, pine and yew trees. No clear evidence of Mesolithic settlements or camp sites in the area has yet been discovered. At the limits of the region, near Lake Inchiquin and at the so-called "Doolin Axe Factory", stone artifacts have been discovered that may be Mesolithic in origin. However, by the Neolithic, c. 4000 BC, settlers had clearly arrived and began changing the landscape through deforestation, likely by overgrazing and burning, and the building of stone walls. These people also constructed Megalithic sites like the portal tomb known as Poulnabrone dolmen and the court tombs at Teergonean (near Doolin) and Ballyganner (near Noughaval). Overall, there are around 70 megalithic tombs in the Burren area, more than half of all of these structures found in Clare.