Culture and Ecology of Chaco Canyon and the San Juan Basin

----------------------96 Chaco Project Synthesisintroduction of ceramics. Those sites with the earliestdirectly dated cultigens tend to be located in areaspresumably near fields and occupied during thegrowing season, a pattern seen elsewhere in theSouthwest. These sites are situated at midelevationson the eastern side of the San Juan Basin; thepatterning of site locations by phase indicatesrepositioning of Archaic groups with numerous SanJose period sites, few Armijo sites, and an increasednumber of En Medio sites in the San Juan Basin.Following Hogan (1994), Vierra noted that thispattern probably reflects a movement of Archaicpeople to different areas at different times rather thanmovement of new people into the Basin.With the discovery of irrigation features in theZuni area (Damp et al. 2002), Vierra (2004) againrevisited the issues relating to the adoption of maizehorticulture across the Colorado Plateau. Hecompared the percentages of archaeobotanical remainsfrom 53 Late Archaic habitation sites (those containingstructures and extramural features) in three areas: thewestern San Juan Basin, the northern San Juan Basin,and the northern Rio Grande valley. He could notsupport the hypotheses that farmers moved into thearea (e.g., Berry 1982) or that the San Juan Basin wassegregated into foragers on the west and farmers onthe east during the Late Archaic (Hogan 1994). Instead,he suggested that agriculture developed atdifferent rates in different environmental locations(earlier in the western San Juan Basin than in thenorthern San Juan Basin or Rio Grande valley).Maize cultivation appeared in both upland and lowlandcontexts. Vierra suggested that early agriculturewould have occurred in well-watered micronichesettings that had low diet-breadth return rates (e.g.,succulents and wild seeds). These microniches wouldinclude floodplains, high-water-table areas, playas,ponds, seeps, springs, or areas where runoff waterfrom mesa tops can be utilized. Those areas adjacentto pinon-juniper woodlands and fall plant resourceswould have an advantage of fewer schedulingproblems in any cost-benefit assessments. Vierra's(2004) analysis lends support to the proposition byGwinn Vivian (1990) that environmental variables areimportant in these early periods.In summary, models for the Archaic adaptationhave been devised and are being evaluated. Becauseit has proven the most useful for the San Juan Basin,many investigators still rely on Irwin-Williams'(1973, 1979) incomplete description of the Osharatradition to evaluate their data. The Chaco Projectdata do fit her model, but it is more likely that theChaco area of the San Juan Basin would not have asdense a popUlation as the peripheries or the ArroyoCuervo region. Its unique setting, however, doesprovide advantages not available immediatelysurrounding this center of the San Juan Basin.