exceptionally smoky. In the northwestern Great Plains and the Plateau region located nearby, climate changes and extreme temperature and weather conditions made it difficult to live year-round. Hot summers led to the building of simple tent-like structures that were portable and could be packed up to move. For cold winter months, pit-houses provided the warm, protected shelter necessary for survival. Cross-cultural patterning A cross-cultural middle range model of pit-house architecture using George Murdock's 1967 Ethnographic Atlas found that 82 of the 862 societies in the sample occupy pit structures as either their primary or secondary dwellings. All but six of the 82 societies live above 32° north latitude, and four of the six cases in this sample that are below 32° north latitude are from "high mountain" regions in east Africa, Paraguay, and eastern Brazil. The last example is from the Yami who occupied a small island south of Formosa. Three conditions were always present among groups in the sample: 1) non-tropical climate during the season of pit structure habitation; 2) minimally a biseasonal settlement pattern; 3) reliance on stored food during the period of pit structure occupation. These conditions may be related to other factors of society and the presence of any or all of these three elements in society does not pre-condition occupation of pit structures. Nonetheless, these three conditions were present in all cases of pit structure occupation present in the Ethnographic Atlas. Other cultural patterns were common, but not universal across the sample. These commonalities include: cold season of occupation, low population estimates, and simple political and economic systems. The ethnographic sample is based almost entirely on case studies from societies located in northern latitudes. The period of pit structure occupation is generally during the cold season, probably due to their thermal efficiency. Dug into the ground, pit structures take advantage to the insulating properties of soil, as well as having a low profile, protecting them from exposure to wind-induced heat loss. Since less heat is lost by transmission than is in above ground structures, less energy is required to maintain stable temperatures inside the structure. Out of the 82 ethnographic cases in the Ethnographic Atlas, 50 societies had population estimates. Of these, 64% had fewer than 100 people per settlement. In only 6% of cases were there more than 400 persons per settlement. The cases with the highest population densities were the Arikara and Hidatsa