A fossil discovery

 It has been suspected by researchers for a long time that hippos evolved from plant eating semi-aquatic mammal.

They couldn't confirm this theory because the ancient fossils were discovered 15 million years ago and this led to the change.

They were led to find fossils because of their curiosity. It was helpful to discover teeth because the molar patterns on a mammals teeth are unique. The ancient mammal weighed 220 pounds. They believe it is a relative to the modern day hippo. It is called the African mammal because zebras, giraffes, lions and antelopes are not from Africa. People think they are but really they aren't. They are from Asia. Except for the hippo the rest of the animals are not from Africa.