The Ice Ages began approximately 1.8 million years ago. These are 100,000 to 130,000 year cycles of global cooling and glaciation, separated by shorter warmer interglacial intervals. It is during the Ice Ages that we see the evolution and radiation of Homo erectus, Homo ergaster and Homo sapiens in Africa, Java and Asia, and Neandertals in Europe. This period is called the Paleolithic, or "Old Stone Age." During the Ice Ages winters may have been slightly warmer, but summers were significantly cooler. As a result there was less temperature variation between summer and winter, less evaporation, and snow did not melt as quickly, causing large inland bodies of water, continental and montane glaciers, and the exposure of large areas of land that today are covered by oceans. Plant and animal communities were very different than today, and large expanses of Utah were covered with woodland that today are desert. There were also 35 species of animals in North America that are extinct today, including mammoths, mastodons, the American horse and camel, Smilodon, the giant Shasta Ground Sloth and the short-faced bear. The first Americans entered the New World during the last Ice Age, at the end of the Wisconsin Glacial Period. Archaeological sites in Alaska indicate this probably occurred between approximately 13,500 and 12,800 years ago via Beringia, a 1,000 mile wide plain between Siberia and Alaska, and moved south through an "ice-free corridor" that formed as large ice sheets covering Canada began receding. By 11,200 years ago, people had spread across all of North and South America.

Utah’s last Ice Age was called the Wisconsin Period, and lasted from approximately 120,000 to 10,000 years ago. Sea levels were sometimes 300 feet lower than today, and large inland glaciers and seas covered much of the northern hemisphere. Summers were much cooler than today, but winters were a bit warmer. In Utah, large areas that are desert today were covered with juniper woodlands and large inland lakes.  Animals that roamed this area included hairless mammoths, wooly mastodons, mountain goats, camels, enormous ice age buffalos, twelve-foot tall ground sloths, short-faced bears bigger than grizzlies, dire wolves, and Smilodon—the giant saber-toothed cat. The first Native Americans moved into Utah at the end of the last Ice Age, and from about 12,000 to 10,000 years ago they hunted Pleistocene mammoths and bison in addition to deer, elk, bighorn sheep and rabbits. These Ice Age hunters are called Paleoindians, and they used stone-tipped darts with atlatls, or wooden spearthrowers. These were the makers of Clovis and Folsom points, and they ranged across North America from Canada to Mexico and from the east coast to the west.

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Last Update: 12/22/08