Just to add a bit more about the Cenozoic era. The Cenozoic era is split up into three periods: the Paleogene, Neogene, and Quatenery periods. Throughout these periods, the Cenozoic is divided into seven epochs (subdivisions of the geologic timescale that are longer than an age and shorter than a period): Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene.
The Paleocene, Eocene and Oligocene epochs occur during the Paleogene period. Paleocene was a time of dense forests and evolutionary experiments due to the extinction of the dinosaurs and other giant reptiles at the end of the Cretaceous. This paved the way for mammals and birds to evolve to fill those empty niches. The Eocene was the time of global warming, with temperatures across the planet soaring. Forests thrived and trees grew even in polar regions. The Oligocene was the start of the global cooling that would eventually shift the Earth 's climate to one where glaciers were present and ice ages were possible. This was the time when grasslands began to expand and forests shrank causing animals to evolve to fit the new open landscape.
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Grasslands continued to expand and forests dwindled during the Miocene. Kelp forests made their first appearance and soon became one of Earth 's most productive ecosystems. Apes also arose and diversified during this epoch. By the end of the Miocene, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path. The Pliocene epoch looked similar to Earth today as North and South America had been drifting closer. The gap between them was sealed in this epoch. As the world cooled in the late Pliocene, ice at the North Pole became permanent and grassland and tundra