to have been abandoned from about 21,000 years ago until after 13,000 years ago, with a burial found at Kendrick's Cave on the Great Orme dating to about 12,000 years ago. Mesolithic Following the last Ice age, Wales became roughly the shape it is today by about 7000 BC and was inhabited by Mesolithic hunter-gatherers. Wales has many sites where Mesolithic material has been found, but securely stratified material is rare. The earliest dated Mesolithic site in Wales is Nab Head, Pembrokeshire, around 9,200 years ago. Many of the sites from this period are coastal, although 9,000 years ago they would have been some distance inland from the sea. There is a particular concentration in Pembrokeshire, but there are also a good number of upland sites, most apparently seasonal hunting locations, for example around Llyn Brenig. Some decorated pebbles found at Rhuddlan represent the earliest art found in Wales. An investigation of post holes at the late Neolithic - Early Bronze Age chambered tomb of Bryn Celli Ddu on Anglesey, published in 2006, gave a radiocarbon dating which placed two of the holes in the Mesolithic period. Neolithic The earliest farming communities are now believed to date from about 4000 BC, marking the beginning of the Neolithic period. Pollen evidence indicates the clearing of forests on an increasing scale during this period. The Neolithic saw the construction of many chambered tombs, the most notable including Bryn Celli Ddu and Barclodiad y Gawres on Anglesey. Three main types of megalithic tomb are found in Wales, the Severn-Cotswold type in the south-east, the Portal dolmen type and the Passage graves which are characteristic of the Irish Sea area and the Atlantic façade of Europe and Morocco. Megalithic tombs are most common in the western lowlands. There is evidence of close cultural links with Ireland, particularly in the Early Neolithic period. A number of houses from the Neolithic period have also been found in Wales, most notably the settlement at Clegyr Boia near St David's in Pembrokeshire. Many artefacts have also been found, particularly polished stone axeheads. There were a number of "factories" in Wales producing these axeheads, the largest being the Graig Lwyd factory at Penmaenmawr on the north coast which exported its products as far afield as Yorkshire and the English midlands. Pottery finds also indicate a relationship with Ireland. The Bronze Age Metal tools first appeared in Wales about 2500