Stahle, David W.; and Hattori, Eugene M., "Possible impacts of early-11th-, middle-12th-, and late-13th-century droughts on western Native Americans and the Mississippian Cahokians" (2007). USGS AbstractOne or more of three intense and persistent droughts impacted some Native American cultures in the early-11th, middle-12th and late13th centuries, including the Anasazi, Fremont, Lovelock, and Mississippian (Cahokian) prehistorical cultures. Tree-ring-based reconstructions of precipitation and temperature indicate that warm drought periods occurred between AD 990 and 1060, AD 1135 and 1170, and AD 1276 and 1297. These droughts occurred during minima in the Pacific Decadal Oscillation and may have been associated with positive values of the Atlantic Multidecadal Oscillation. Each of the Native American cultures was supported, to a greater or lesser degree, by precipitation-dependent resources. Both the Four Corners region and Cahokia were sites of intense growth between about AD 1050 and 1130, and by AD 1150, cultures in both regions were undergoing stress. By AD 1300 the Anasazi and Fremont cultures had collapsed and their residual populations had either left their homelands or withered. In the case of Fremont populations, the AD 990-1060 drought may have had the greatest impact. This drought also may have affected the Anasazi, for it was at the end of this drought that some people from Chaco migrated to the San Juan River valley and founded the Salmon Ruin great house. Detailed data do not exist on the number of Lovelock habitation sites or populations over time; however, Lovelock populations appear to have retreated from the western Great Basin to California by AD 1300 or shortly thereafter. Published by Elsevier Ltd.

Harsh high-altitude environments were among the last landscapes to be settled by humans during the Late Pleistocene between ∼15,000 and 11,000 calendar years before present (cal yr BP). Successful colonization required physiological adaptations to hypoxia and cultural adaptations to limited resources and cold temperatures. How and when humans colonized Andean South America has been poorly understood owing to controversial early archaeological sites and questions about the impact of environmental factors, including the presence of glaciers. Here we report the reexamination and direct dating of six finely woven textiles and cords from Guitarrero Cave, Peru, that identify South America's earliest textiles and show that occupation of the Andes had begun by ∼12,000 cal yr BP. Additional evidence for plant processing and fiberartifact construction suggests women's presence among these earliest foraging groups. Previous research suggested use of the highlands by small groups of male foragers between 15,000 and 13,000 cal yr BP with permanent settlement only after 11,000 cal yr BP. Together these data amplify accumulating evidence for Late Pleistocene/Early Holocene technological sophistication and cultural diversity in South America and are consistent with hypotheses that long-term settlement of higher elevations occurred immediately following glacial retreat.

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Despite ranking at the low end of the continuum in net caloric benefit relative to other foods, small seeds assumed great dietary importance in many parts of the world, including western North America. In a series of publications, Adovasio (1970a, 1974, 1980, 1986) argued that coiled basketry technology was invented in the eastern Great Basin during the early Holocene as a specialized food-processing technique. Coiled baskets are indeed useful for collecting and processing seeds, but it does not necessarily follow that they were originally designed for this purpose. A whole basket recently discovered at Cowboy Cave in southeastern Utah returned an AMS radiocarbon assay of 7960 ± 50 B.P., making it currently the earliest directly dated coiled basket from the Americas. This basket is not a parching tray and likely had nothing to do with harvesting seeds. We discuss the implications of this find with regard to tracking the temporal spread of coiled basketry technology in western North America and the role of coiled and twined forms in the initiation of small seed exploitation. Coiled and twined baskets for small seed processing may result from reconfiguration of existing technologies to create novel forms suited to a new food exploitation strategy.

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