When I initially proposed that the square, plaza-facing rooms at Chacoan great houses that have features suggesting residential use represented an alternative to residence in kivas, I speculated that the difference between the two patterns might reflect some meaningful social difference within Chacoan society, perhaps different ethnic or geographic origins. I’m still willing to entertain that idea as a hypothesis, but after looking a bit more closely at the development of the well-documented great houses I think it’s more likely that what we see here is a difference over time, with different styles of residential architecture predominating in construction projects dating to different periods. Basically, it looks like the earliest great houses generally have subterranean kivas associated with suites of rectangular rooms, which is the standard pattern at small houses as well. There are typically fewer kivas than there are room suites, which suggests that kivas might have been shared by multiple households (extended families?) living in close proximity. At some point, however, probably in the tenth century, a new style emerged in which the kiva was replaced by an above-ground but single-story square room backed by two or three two-story (or even three-story) rooms that were smaller and more rectangular. These are the “linear suites” well-known to Chaco architecture scholars. It’s unclear how prevalent they were, and it doesn’t seem that they were ever universal at all great houses, but a substantial amount of great-house construction in the late 900s seems to be of this type, with no new kiva construction and older kivas possibly falling into disuse.
At some sites this pattern persists well into the late 1000s, such as at Salmon, and in general it seems to be typical at many later great houses with very formal, rectilinear, symmetrical layouts. At some point, however, it seems to have been supplemented and ultimately replaced by a new pattern of building round kivas into aboveground square rooms, which in some ways seems like a combination of the two styles. In some cases these kivas were actually built into what appear to have been square living rooms that had been built earlier; this is what happened at Salmon in the post-Chacoan era, but it also seems to have happened in some cases at Pueblo Bonito, probably still within Chacoan times. Other examples of these “blocked-in” kivas were clearly built as units, with the square enclosure and the circular chamber built together. It’s not clear exactly when this change happened, but it was probably in the late 1000s or early 1100s, right at the peak of Chaco’s power and influence or shortly thereafter. Later, and definitely after Chaco’s decline, a new pattern arose, with kivas and associated surface room blocks strongly resembling those at small houses being built into the plazas of Chacoan great houses. This probably also involved additional building of new kivas into older Chacoan square or rectangular rooms. It’s not clear how long this persisted, as these late units are very hard to date, but it may well have gone on into the 1200s.
Any of these changes through time may well have been associated with changes in regional influence or social dynamics, and I’ll be looking into the possibilities for explaining them, but I think it’s pretty clear that there’s a strong temporal component to these differences in architecture. One implication of this is that while the large numbers of visible kivas at Chacoan sites have led to an idea that Chacoan architecture is associated with lots of kivas, it may well be the case that the most “Chacoan” innovation in domestic architecture is precisely a lack of kivas, and that this is not obvious today because it didn’t take and after a period of kivaless construction people, including Chacoans, went right back to building (and living in) kivas. I’ll be thinking about and looking into other potential implications for understanding the Chaco system and its place in the broader region.