Both Modern and Neanderthal people were present in the area before the last glaciation between 100,000 and 10,000 years ago, and humans returned as the ice retreated northwards. The archaeological record is poor until about 20,000 years ago, partly because of the prevailing conditions, but also because the coastline was much further north than at present. As the ice retreated during the Mesolithic, the sea level rose, filling what is now the North Sea.