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During the last 2.6 million years, ice ages, also called glacial age they were times of extreme cooling of the Earth's climate where ice sheets and other types of glacier expanded to cover large areas of land. Between ice ages there were warmer periods and we are now living during such a time There have been many ice ages during the last 2.6 million years but when people talk about the Ice Age, they are often referring to the most recent glacial period, which peaked about 21,000 years ago and ended about 11,500 years ago.What causes ice ages is not completely understood. The composition of the atmosphere, changes in the position of our planet around the sun, and changes in ocean currents are some of the important factors that control the climate.The Sabre-toothed tiger, or smilodon, weighed about 450 lbs (200 kg) and had 7 inch (17 cm) fangs. They lived in North and south america and were one of many types of saber-toothed cats that roamed the planet. The Sabre-toothed tiger had short legs, a bobbed tail and lived in shrubby grasslands. It was a carnivore and may have preyed upon animals as large as mastodons!.The woolly mammoth had a thick undercoat that the mastodon didn't have and its tusks were curved, unlike the straight tusks of the look-a-like mastodon. It lived in North America, Northern Europe and lived on grasses, shrubs and other low-lying plant life. While most woolly mammoths became extinct 12,000 years ago, some managed to survive on Wrangle Island, a Russian island in the artic ocean, up to about 4,000 years ago.