Thus far we have glanced at Europe only. But the same changes are taking place in Asia, the cradle and home of most placental mammals, the main area of a huge zoological province of which Europe was but a westward projection, and with which America had direct connection from time to time in the region of Behring's Straits. Here, during late Miocene and early Pliocene times, in the latter part of the Cenozoic era, a dryer and somewhat harsher climate had been accompanied by the appearance of wide plains fitted for grazing animals, as well as stretches of forest, with all varieties of landscape favoring great diversity as well as abundance of mammalian life. It was, perhaps, the golden age for most mammals, when food was plenty, climate not too severe, and every prospect pleased. This slow and gradual, but fairly steady, lowering of temperature was to culminate in the Great Ice Age of the Pleistocene Epoch, so destructive to mammalian life in the northern hemisphere. A second climatic change, perhaps even more important than the lowering temperature, was the increase of aridity. Even during the Oligocene Epoch "the flora indicates a lessening humidity and a clearer differentiation of the seasons,"[7] The great trough of the inland sea which had stretched from the Mediterranean to the Indian Ocean began to rise, the first uplift taking place along the Pyrenees and western Alps. The Miocene was marked by a series of great movements. The old inland sea was displaced, subsidence gave place to uplift, and the greatest mountain system of the globe, including the Alps and the Himalayas, began to grow through vast repeated uplifts in the crust.[8] The continents were elevated and widened. The forest-dwelling types became restricted and largely exterminated, and animals of the plains, in the form of horses, rhinoceroses, and the cloven-hoofed ruminants, expanded in numbers and in species. This profound faunal change implies dryer climate. There was now a lesser area of tropic seas to give moisture to the atmosphere. The mountains were now effective barriers, shutting off the moisture-bearing winds from the interior of the continents. These changes would have been noticeable in Europe north of the Alps, but were far more so in central Asia along the northern face of the great plateau of Thibet, with its eastern and western buttresses, and its towering rampart of the Himalayas on the south, cutting off the warm moisture of the Indian Ocean. Northward of this vast plateau and westward over the far less elevated Iranian plateau and Afghanistan, forest was fast being replaced by parklands of mingled groves and glades, or by grassy plains, or even by dry steppes. Dessication, aridity of climate, was fast compelling forest and arboreal mammals to migrate or radically change their habits of life.[9]