The first known settlement of Dorset was by Mesolithic hunters, who returned to Britain at a time when it was still attached to Europe by a land-bridge, around 12,500 BC. The population was very small, maybe only a few thousand across the whole of Britain, and concentrated along the coast: in Dorset, such places as the Isle of Purbeck, Weymouth, Chesil Beach and Hengistbury Head, and along the Stour valley. These populations used stone tools and fire to clear some of the native oak forest for herding prey. Genetic experiments carried out on a Mesolithic skeleton from Cheddar Gorge (in the neighbouring county of Somerset) have shown that a significant part of the contemporary population of Dorset is descended from these original inhabitants of the British Isles.