As late as 1625 most European houses had a tamped earthen floor. It was with the industrialization of the forest that wood floors began replacing the earth.  And now the concrete floor systems are replacing wood floors. The hardness and flatness of conventional flooring are strange for our feet and actually may be the cause for back, hip and knee injuries. Earthen floors are soft, leathery and cool and are most pleasant on the feet when they have regular imperfections in terms of how level and smooth they are. One of their main characteristics is its thermal mass meaning it will help moderate indoor temperature fluctuations by absorbing and slowly releasing heat.