Culture and Ecology of Chaco Canyon and the San Juan Basin

The Preceramic Period 63En Medio phase (800 B.C. to 400 A.D.). Thisphase represents continuity and change in the BasketmakerII adaptation of the Anasazi sequence. By 800to 600 B.C., Irwin-Williams (1973: 12) suggested thatthere was an increase in regional population growth,which peaked in the early centuries of the ChristianEra. Slab-lined storage pits are present, and there isan increasing emphasis on ground stone tools. Troughand flat metates and long manos also appear near theend of this period. In addition to the canyon-headcliff-base sites, settlements on dune ridges appear;these are thought to represent sites utilized during theseasonal round during which a number of wild plantscould be gathered between April and September.Trujillo phase (A.D. 400 to 600). This isthought to be a continuation of the En Medio phase; itis distinguished by the introduction of the bow andarrow, as well as ceramics. It represents a BasketmakerIII adaptation.Concurrently, studies of the Paleoindian andArchaic adaptations east of the San Juan Basin wereunder way. Judge (1973) focused on the Paleoindianadaptation in the central Rio Grande Valley, where heevaluated four cultures (Clovis, Folsom, Belen, andCody complex) that differed distinctly from Archaiccultures. Hafting of projectile points to the foreshaftof the atIatl dart during the Paleoindian period involvedgrinding the base of the projectile to fit into abone foreshaft. In contrast, Archaic points wererigidly affixed to a wooden foreshaft with a sinewbinding. Judge (1973:325) considered the formerbetter suited for hunting large animals and the latterfor smaller game. Differences in scraper types, lithicdebitage, and lithic raw materials between theseperiods were noted (Judge 1973:56-57). Judge (1973:301), however, saw a cultural continuum betweenCody and the subsequent Early Archaic (Jay) periods.The Archaic adaptation in the Rio Grande wasaddressed by Reinhart (1968), who surveyed andexcavated eight sites (including one cave). He outlinedculture changes from the previously definedAtrisco phase (pre-WOO B.C.) through his newlynamed Rio Rancho phase (1000 to 1 B.C.) andAlameda phase (1 B.C. to A.D. 500). Both Reinhartand Judge attributed changes in these cultures initiallyto environmental shifts; as moisture decreased, thetypes of fauna and flora changed and the localpopulations adjusted to these new subsistenceresources. Cultural factors also played a role in theshifts from big game hunting to hunting and gatheringand from hunting and gathering to horticulture.Chaco Project StudiesGillespie'S (1985) analysis of thepaleoenvironment suggested that the Chaco area wasprobably relatively unproductive for people livingduring the Paleoindian period. He predicted that theFour Comers area and land to the south and eastwould have had greater precipitation and mildertemperatures than the central San Juan Basin. As aresult, in those areas there would have morebiodiversity to support large game animals and usablefloral resources. One would expect) therefore, fewerPaleoindian sites in and around Chaco Canyon than inareas surrounding the central San Juan Basin.During the Archaic, or Middle Holocene, whichcorrelates with the Jay-Bajada periods, moist summerswould have provided a greater abundance of plant andanimal resources. Pinon nuts would have been availablefor the first time, and bison populations wouldhave achieved their peak population sizes in the SanJuan Basin (Gillespie 1985). These conditions, whilemuch better suited for hunter-gatherer populations,would not be as good in and around Chaco Canyon asthey would have been in the Arroyo Cuervo area tothe south and east (Irwin-Williams 1973).During the Late Archaic (Irwin-Williams's SanJose and Armijo phases), Gillespie (1985) suggesteda change to less mesic, but cooler, conditions. As aresult, exploitable resources would have been lessabundant. It is during the Armijo phase (1800 to 800B.C.) that Irwin-Williams noted the introduction ofmaize in the Arroyo Cuervo area, the use of rockshelters,and a probable seasonal aggregation of peopleinto larger social units.In summary, there should be differences in thedensity of popUlations (as represented by the numberof types and sites) in Chaco Canyon versus the ArroyoCuervo area. Gillespie (1985) suggested similaritiesin adaptive patterns in these two areas.