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winters that reduced the growing season by several weeks. Within that time, two colder <br />phases have been identified (Figure 5). The first began around AD 1300 and continued until <br />the late 1400s. It was followed by a slightly warmer period in the 1500s. Then, a marked <br />decline in temperatures occurred between AD 1600 and 1800, which was the height of the <br />Little Ice Age. The cause is unknown, but the coldest part, ca. AD 1645 to 1715, was <br />coincident with an episode of low sunspot activity, and solar cooling, called the Maunder <br />Minimum 2 (Eddy 1976). During that time, the Northern Hemisphere was about 1E Celsius <br />colder than present. <br />Figure 5. <br />Fluctuations in <br />temperatures during <br />the Little Ice Age. <br />(After Lamb 1969 <br />and Schneider and <br />Mass 1975.) <br />The environmental effects of prolonged periods of cold temperatures creates <br />significant impacts on growing seasons of domesticated plants and would have lowered <br />elevation levels of primary floral resources. It can also have devastating effects on trees; <br />and, although cooler and moister temperatures are generally good for the spread and growth <br />of pinyons, the cold extremes of the 17th century would likely have reduced pine nut <br />production and affected the growing cycle of new trees. These temperature levels coupled <br />with deep snows would have produced significant die-off of large mammal populations, as <br />well. Because of these factors, the approximate 100 year dip in temperatures between ca. <br />AD 1600 to 1700 – with a low mark about 1640-1650 – may have driven aboriginal Numic <br />populations south and west to warmer climates in New Mexico, Arizona and Utah. <br />A migration to the south would have brought the Numic groups into close contact <br />with Europeans, and perhaps fostered new alliances with Apaches, Navajos, and Pueblos. <br />Horses were likely acquired during that time. New trading relationships were forged and <br />new technologies acquired. With the acquisition of the horse came the reduction and <br />ultimately the demise of the production of Uncompahgre Brown Ware. If this is truly a <br />parallel occurrence, then a record of thermoluminescent dates for this ceramic should reflect <br />the transition to a horse-riding culture. <br />33