2012-06-06 21:13:40
After the extinction of the dinosaurs 65 million years ago, Earth’s climate was hot and humid, and vast tracts of forests and jungles covered much of the planet. But during the Miocene, between twenty-three and five million years ago, the cooling of the Earth, due among other factors to the growth of the Antarctic ice cap, caused a loss of humidity that favored the spread of grasses to the detriment of the trees. This is how the first sheets appeared.
The savannah is a very rich ecosystem. Grass is a highly productive natural resource. The grass, unlike the vast majority of plants, does not grow from its end, but from its base; In this way, its growth is not interrupted by the consumption that herbivores make of it. A large number of animal species live on grass. But grass contains silica, a very abrasive mineral, so grazing animals must develop thick teeth to compensate for the wear and tear they suffer.
On each continent, the mammals present before climate change evolved in parallel to adapt to the new ecosystem. Thus, fast grazers appeared, such as gazelles and modern horses, large mammals such as elephants and rhinos, and tall mammals, such as giraffes, adapted to feed on the highest branches of the trees that dot the savannahs.
In North America, many of these animals evolved from primitive horses and camels, native to this continent, as well as antilocaprids, ancestors of the pronghorn, the only North American antelope.
But towards the end of the Miocene the climate became colder and drier, and the savannahs were replaced by grasslands and steppes, and many of these species disappeared. Thus, camels and horses disappeared from their continent of origin, North America. Horses survived in the great plains of Eurasia and, in the form of zebras, in Africa, and camelids were restricted to desert areas of the Old Continent (camel and dromedary) and mountainous areas of South America (llamas, guanacos…)
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