Cob is an earthen building material that is made of clay, sand, straw, and water. It has been used for thousands of years to construct homes and buildings. It has been used worldwide, but has only recently started to attract interest from Western countries. Cob has its origins in millennia of traditional building, in some of the oldest permanent human dwellings. Humans have made shelters this way for so long that we may carry a genetic memory of how to do it.