For perhaps several thousand years following the first migrations little of great significance developed. There undoubtedly was cultural progress, but it was slow, and in the long perspective of time its evidences are hardly discernible. With the knowledge and benefits of agriculture, which was probably developed first in Mexico, hunting gave way to husbandry, nomadism to sedentary life, and there followed a great period of change and advancement. The introduction of corn or Indian maize into what is now the southwestern United States may be called the antecedent condition for all advanced cultures of the area. Evidence has not yet been established that the first of the maize-growing Indians of the Southwest were permanent occupants of the Mesa Verde. Nevertheless, in the Cliff Palace cave, well below the horizon or floor level of the cliff dwellers, archeologists have found a yucca fiber sandal of a distinctive type which is associated only with the first agricultural civilization. From this evidence it would be reasonable to assume that the caves of Mesa Verde at least offered temporary shelter, if not permanent homes, to the people of this period. The earliest culture so far definitely identified as having permanent habitation on the Mesa Verde is the Basket Maker III or the Second Agricultural Basket Maker first found in Step House cave on the west side of the park below the debris of the latter cliff-house occupation. Recent excavations and archeological surveys furnish conclusive evidence that the second agricultural people were most numerous in the area now included in this national park, and they constructed their roughly circular subterranean rooms not only in the sandy floor of the caves but also in the red soil on the comparatively level mesas separating the numerous canyons. Late Basket Maker House A, formerly known as Earth Lodge A, is an example of this early type of structure. Up to this time excavations have failed to uncover a single house structure of this type not destroyed by fire. These early inhabitants made basketry, excelled in the art of weaving, and it is believed were the first of the southwestern cultures to invent fired pottery. The course of this invention can be traced from the crude sun-dried vessel tempered with shredded cedar bark to the properly tempered and durable fired vessel.