After the age of dinosaurs had ended about 65 million years ago mammals became the largest animals to
the earth. Rhinos and elephants however were much larger than they are today. Huge mammals weighed almost 17 tons. The biggest mammal of our
, the African elephant, by comparison , weighs only about 6.5 tons.
When dinosaurs were on earth mammals were small
that stayed the same in size for over 150 million years. The journal Science
that after dinosaurs had become
, mammals became larger and larger but then stopped growing.
In the 1990s, a French team
prehistoric fossils in Baluchistan, the area between Iran, Afghanistan, and Pakistan. The fossils belonged to an extinct hornless rhinoceros , the Baluchitherium , which lived about 40 million years ago. It was 5 meters tall and had the
of three elephants.
Scientists are not sure how mammals got that big. During the age of dinosaurs, they often had to fight for food and
as food for the giant reptiles themselves. When the dinosaurs
nobody was there to eat the leaves of trees and plants. For the first time, mammals had plenty of food to eat.
Why mammals stopped growing is still a
. One theory claims that continents became smaller and there wasn’t enough land
. According to other experts, a colder climate led to the death of dinosaurs. Mammals grow best in cold weather because bigger animals can
the heat better.