Pueblo Bonito is divided into two sections by a precisely aligned wall which runs north to south through the central plaza. A
Great Kiva is situated on either side of the wall, creating a symmetrical pattern common to many of the Great Houses. In addition to the Great Kivas, over thirty other kivas or ceremonial structures have been found, many also associated with the large central courtyard. Interior living spaces were quite large by the standards of the Ancient Pueblo. The site covers and incorporates approximately 800 rooms. In parts of the village, the tiered structure was four and five stories high. During later construction, some lower level rooms were filled with debris to better support the weight of the upper levels. The builder's use of
core-and-veneer architecture and multi-story construction produced massive masonry walls as much as thick. Population estimates for the village vary. During the early 20th century, the structures were viewed as small cities, with people residing in every room. From this perspective, Pueblo Bonito could have accommodated several thousand inhabitants at its peak. Recent analysis has lowered the estimated population to less than 800, primarily due to the small number of usable hearths in the ruins. An analysis based on architecture estimated the resident population at 12 households, or about 70 people at its peak. These tend to be located on the ground floor, near the central plaza, and are associated with entrances to a series of rooms going deeper into the structure. Rooms were connected by a series of interior doorways, some of them in a T-shape. A family may have inhabited 3 to 4 rooms, with many small interior spaces being used for storage. There was generally no outside access to the room blocks other than from the central courtyard. It is possible that Pueblo Bonito is actually neither a village nor city. While its size has the capacity for a significant population, the environment may not have been ideal for sustaining a large population. Excavations at the site have not revealed significant trash middens indicating residential areas. A common suggestion is that Pueblo Bonito was a ritual center. This is evident in not only the existence of the kivas (which are more often than not attributed to ritual function) but also the construction of the site and its relation to other Chaco Canyon sites. Although there were many occupants, only 50-60 burials were found here. The site indicates the Puebloans' comprehension of solar and lunar cycles; both of which are marked in the petroglyphs of the surrounding cliff area as well as in the architecture of Pueblo Bonito itself. Examination of
pack rat middens revealed that at the time that Pueblo Bonito was built, Chaco Canyon and the surrounding areas were wooded by trees such as
ponderosa pines. Evidence of such trees can be seen within the structure of Pueblo Bonito, such as the first-floor support beams. Scientists hypothesized that during the time when the pueblo was inhabited, the valley was cleared of almost all of the trees, to provide timber for construction and fuel. This tree removal, combined with a period of drought, led the water table in the valley to drop severely, making the land infertile. This explains why Pueblo Bonito was inhabited for only about 300 years and is a good example of the effect that
deforestation can have on the local environment. The Ancestral Puebloans, no longer able to grow crops to sustain their population, had to move on. == Matriliny ==