Repeated glaciations, which covered the entire land mass of modern Scotland, destroyed any traces of human habitation that may have existed before the Mesolithic period. It is believed the first post-glacial groups of hunter-gatherers arrived in Scotland around 12,800 years ago, as the ice sheet retreated after the last glaciation.[32][33]
Groups of settlers began building the first known permanent houses on Scottish soil around 9,500 years ago, and the first villages around 6,000 years ago. The well-preserved village of Skara Brae on the mainland of Orkney dates from this period. Neolithic habitation, burial and ritual sites are particularly common and well preserved in the Northern Isles and Western Isles, where a lack of trees led to most structures being built of local stone.[34]