Since most Pueblo Indian ceremonial exists to implore help for the increase of the fertility of all created things, including the increase of human beings, all important rites and dances take place either before the time of planting or after the harvest is gathered; consequently the summer settlements rarely, perhaps never, had _kivas_ or ceremonial chambers; this fact is an aid in determining the temporary or permanent character of the ruins scattered over the plains.[117] Various were the causes for the abandonment of these prehistoric dwellings. Some of the houses found were evidently of only temporary usefulness—way-stations in a pathless wilderness. Some settlements perhaps were near water sources long since overwhelmed by drifting sand. Prolonged drought often was the primary reason for moving. The hostilities of other tribes would drive a people from a location not easily defended. The failure of grain crops or of other nutritive or medicinal plants would generally be considered a sign from the gods that the place was accursed. Any prolonged disaster, whether it were drought, or flood or disease, was usually attributed by the Pueblos to witchcraft. Many secret crimes committed in retaliation have contributed slowly but surely to the depopulation of whole villages. The pueblo of Sía is said to owe its decline in comparatively recent time to constant “inter-killing going on for supposed evil practices of witchcraft.”[118] Originally, it is believed by some writers, the two divisions of the race known as those of the Plains and those of the Pueblos were one and the same, the Pueblo Indians being merely “fragments” of wandering tribes left behind on both banks of the rivers that coursed through the plains. Differing environments effected great contrasts in the lives of the two peoples. The hunting of the buffalo largely determined the habits of the Plains Indians. That animal furnished a steady supply of meat in contrast with what could be got by the Pueblos from the occasional hunt of small game; his skin dried in the sun made an excellent tent, in place of the brush or adobe shelter; his fur made warm and durable clothing, whereas the Pueblos had to depend upon wool and cotton garments. From the horns drinking-cups were fashioned.[119]