It will be found on examination that these prehistoric buildings were constructed on certain universal lines, reproducing with startling similarity types which are world-wide. It will also be found that habitations or buildings devoted to certain utilitarian purposes have one form, while sacred buildings have another, following a law geographically widespread. Man shares with the animal a desire for protection for his family or food accumulated or awaiting consumption. This holds true among agricultural peoples whose food is cereal and can be stored indefinitely or prepared for use when necessary. It is not necessary to suppose that man learned the habit of storing food from bees and squirrels; the same needs produced the same habits. The earliest storage places adopted by man were caves, trunks of trees or pits dug in the earth, the first mentioned being the most common. The first step taken to improve this storage place was the construction of a wall to close the entrance to the cave or pit. A further modification, practically an expansion of this simple idea, led to the construction of an elaborate dwelling having rooms specialized for different economical purposes within the shelter of the cave. This same idea of protection led to another line of development in which the cave is wanting. The construction of a stone cairn in the open would also serve for protection of the food supply. Such a building, erected simply for storage, naturally drew about it subordinate rooms for dwellings, at first temporary in structure but later, as ability in stone-working improved, permanent buildings or community-houses of durable material. This second type of prehistoric building, erected independent of caves, evolved along lines different from the first; in forms of construction the two types are similar, but they differ as to sites; one became a cliff or cave dwelling; the other, what is called a village or pueblo.