The first mammals probably evolved from reptiles about 200 million years ago during the Mesozoic period. They were rather small in a time when dinosaurs ruled the lands. When the dinosaurs died out about 65 million years ago mammals became the dominant land animals. Many mammals became extinct during the Ice Age , which ended thousands of years ago.
Today, some species are in constant danger of becoming extinct because they are hunted by humans. Hunters and poachers earn money by selling fur, tusks and other parts of mammals. Larger wild animals are often brought to zoos where they are protected.
Artist's image of wooly mammoths during the Ice Age