million years of water and ice with a wide fertile valley between them, and a newer, wilder western terrain. With Scotland now in the northern temperate zone, it was subjected to numerous glaciations in the Neogene and Quaternary periods, the ice sheets and their attendant glaciers carving the landscape into a typical postglacial one, overdeepening river valleys into the characteristic U-shape and leaving the upland areas covered with glacial corries and dramatic pyramidal peaks. In lowland areas the ice deposited rich fields of fertile glacial till and eroded the softer material surrounding the extinct volcanoes (particularly the older Carboniferous ones), leaving many crags. Before modern humans During the last interglacial, around 130,000–70,000 BC, there were times when the climate in Europe was warmer than it is today, and after the Neanderthals came to prominence there was another mild spell around 40,000 BC. Neanderthal sites have been found in the south of England from this era, though no traces of early modern humans have been found. Glaciers then scoured their way across most of Britain, and it was only after the ice retreated about 15,000 years ago that Scotland again became habitable. Hunter-gatherers As the climate improved, mesolithic hunter-gatherers extended their range into Scotland. The earliest evidence to date is the flint artefacts found at Howburn Farm, near Elsrickle in 2005. This is the first and so far the only evidence of Upper Paleolithic human habitation in Scotland, around 12,000 BC, which appears to fall between the Younger Dryas and Lomond Stadial periods when cold conditions returned relatively briefly. An early settlement at Cramond, near what is today Edinburgh, has been dated to around 8500 BC. Pits and stakeholes suggest a hunter-gatherer encampment, and microlith stone tools made at the site predate finds of similar style in England. Although no bones or shells had survived in the acidic soils, numerous carbonised hazelnut shells indicate cooking in a similar way to finds at other Mesolithic period sites, including the slightly earlier Star Carr and the Howick house in Northumberland, dated to 7600 BC ("Britain's oldest house"), where post holes indicate a very substantial construction, interpreted as a permanent residence for hunting people. This suggests that hunter-gatherers could also have settled down in Scotland. Other sites on the east coast and at lochs and rivers, and large numbers of rock shelters and shell middens around the west coast and islands, build up a