We live today towards the end of an interglacial period. During inter-glacials there was glacial melt-off, followed by a re-flooding of the ocean to roughly the current level. There was massive ice buildup in the Northern Hemisphere during the former with a concomitant shrinkage of oceans and severe drop in ocean shorelines. Such extreme environments developed with the great continental glaciations that cycled at roughly 100,000 year intervals between cold glacial and warm interglacial phases. From there it continued into the cold, but fertile environments formed through glacial action and on into the most inhospitable of cold environments: the tundra, the alpine, and the polar deserts. It proceeded stepwise into tropical savanna, dry grasslands at low latitudes, and then either into the deserts or into temperate zones at higher latitudes and altitudes. The evolutionary journey of mammalian families that succeeded in adapting to the cold north began in moist tropical forests. Minor glacial events building up to the major glacial periods characterized the latter part of the Pliocene epoch. The Pleistocene epoch is the latter half of the Ice Ages and is characterized by major continental glaciations, which began about two million years ago. It is this which gave rise to their oddness in shape and biological eccentricity, which shaped many into giants, and which ushered in the Age of Man. Their novelty resides in novel opportunities and seasonal resource abundance in the environments shaped by these glaciers. Rather, in the sheer exuberance and breadth of their adaptations, they reflected both the new ecological riches and soil fertility generated by glacial actions as well as the long successions of biomes they evolved in prior to life in the face of glaciers. They did not merely adapt to the increasingly seasonal climates and greater extremes in temperature and moisture. In their biology and appearance they diverged from anything seen earlier in the long Tertiary, the Age of Mammals. During the latter half of the Ice Ages, the Pleistocene, in response to the slow pulsation of continental glaciers, there evolved unique large mammals-man included.
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