Adaptation to the savanna was well in place by 1.7 million years ago .
对大草原的适应在170万年前就已经演化妥当。
Because perhaps on so vast savanna .
也许因为在如此辽阔的热带草原上。
The savanna elephant weighs between six and seven tons , roughly double the weight of the forest elephant .
草原象的体重在6吨至7吨间，大约是森林象的2倍。
Other consequences are more obvious . Deforestation of the amazon rain forest disrupts regional cycles of evaporation and condensation , raising the possibility that earth 's lungs could become a savanna .
