Imagine trying to tell a story without being able to place events in order from beginning to end. In order to trace changes through time, archaeologists must first determine the ages of different sites. The archaeologists involved in this research focused on pottery to date sites, studying thousands of whole pots and potsherds (fragments of pottery vessels) in existing museum collections. The pottery had been recovered from dozens of sites throughout the southern Southwest. The researchers’ findings allowed them to date sites with much greater precision, providing a clearer perspective on how Hohokam culture changed after A.D. 1300.
In the Southwest, most dates assigned to pottery rely on tree-ring dating or dendrochronology. Trees usually add yearly growth rings. For conifers (pines, firs, and spruces), a wide ring indicates a wet year, and a narrow one marks a dry year. Because archaeologists have traced the history of wet and dry years over a period of centuries, they can match the pattern of narrow and wide rings in wooden construction beams found in archaeological sites.
Archaeologists have observed that certain kinds of pottery were associated with certain date ranges. Specimens of a kind of pottery found in sites without tree-ring dates are assumed to be the same age as specimens of the same kind of pottery found at sites with tree-ring dates. Often, pottery in the desert (where pines, firs, and spruces are usually absent) has been dated as a result of being found with tree-ring dated pottery made in the mountains or on the Colorado Plateau.
Using Pottery to Date Sites
The dominant painted pottery at late Hohokam sites is called Roosevelt Red Ware. When this research project began, Roosevelt Red Ware could be divided into three basic types based on decoration:
Pinto Polychrome, A.D. 1280-1330
Gila Polychrome, A.D. 1300-1450
Tonto Polychrome, A.D. 1340-1450
Most late sites in the Hohokam region have large quantities of Gila Polychrome, some Tonto Polychrome, and no Pinto Polychrome. Thus, most sites could be placed between 1300 and 1450, but archaeologists found it difficult to determine which dated earlier in this 150-year period, and which were the latest sites.
After analyzing whole vessels and potsherds found at dozens of sites, researchers have recently been able to define new pottery types that used to be lumped into Gila Polychrome and Tonto Polychrome. This allowed them to break the period between 1300 and 1450 into smaller segments, revealing which sites were occupied at the same time, and identifying the latest prehispanic sites in the region. These new types include:
Cliff Polychrome, A.D. 1350-1450
Nine Mile Polychrome, A.D. 1375-1450
Phoenix Polychrome, A.D. 1375-1450
Los Muertos Polychrome, A.D. 1400-1450
Archaeologists can date sites using pottery.
Archaeologists can determine the age of a pottery type using tree-ring dating.
Changes through time in painted decoration and bowl shapes have helped archaeologists define a number of new pottery types.
These new pottery types can be used to more precisely determine how long different sites were occupied, helping archaeologists track changes in population.