Aboriginally, the Yuit lived in permanent settlements, which they left as the season dictated for hunting, fishing, or bird-catching camps nearby. For centuries the basic dwelling was a semisubterranean sod-covered, driftwood structure with a below-ground tunnel entrance designed to conserve heat. Such structures were large enough to house an extended Family. During the nineteenth century Yuit living on the Siberian shore began to use the walrus-hide-covered winter structure of the nearby Maritime Chukchee, and this type of housing spread to St. Lawrence Island. For both groups, the typical summer dwelling was a skin tent in both the permanent settlements and seasonal subsistence camps. Houses constructed of imported lumber began to appear early this Century in a style and of materials much less well adapted to the severe winter weather than had been the aboriginal dwellings.