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Age of Mammals

Evolution of mammals

ElasmotheriumElasmotherium New kinds of mammal evolved to eat different types of food—plants, insects, other animals and so on—in different habitats all over the world. But over the 210 million years since mammals first appeared, many of those habitats have changed as well. Mammals adapted for life in the forest, for example, died out as their sources of food slowly disappeared as grassland took their place. On top of that, the continents have slowly shifted around the globe. Different species of mammal evolved on different continents separated by seas. Sometimes, when continents became joined together, mammals crossed from one to the other by a “land bridge".

North African mammals, about 35 million years agoNorth African mammals, about 35 million years ago


Over the thousands of millions of years since life began, all types of animals—not just mammals—have very gradually changed in some way. They may, for example, have grown claws or fins, developed wings, lost teeth, or simply become taller. We call this process evolution. The story of mammals, since they first evolved from reptiles about 210 million years ago, is really the story of their evolution.

Early mammalsEarly mammals

Early mammals

Andrewsarchus, from Eocene Asia, was the largest-known flesh-eating mammal that ever walked on land. It was 4 m (13 ft) long.

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