The apes arose and diversified during the Miocene epoch, becoming widespread in the Old World. In fact, by the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path. As in the Oligocene before it, grasslands continued to expand and forests to dwindle in extent. In the Miocene seas, kelp forests made their first appearance and soon became one of Earth's most productive ecosystems.
What the Earth was like
Reconstruction of the Earth in the Archean era, 3.8 billion - 2.5 billion years ago. Credit: Dr Ron Blakey, NAU Geology.
Causes of extinctions
During this period the following extinction level events are thought to have occurred.
Flood basalt eruptions
Flood basalt eruptions are a type of large-scale volcanic activity, both in terms of extent and duration, that can occur on land or on the ocean floor. A flood basalt may continue to erupt for tens of thousands - possibly millions - of years and the lava can cover hundreds of thousands of kilometres.
Earth's climate is not constant. Over geological time, the Earth's dominant climate has gone from ice age to tropical heat and from steamy jungles to searing deserts.
Impact events, proposed as causes of mass extinction, are when the planet is struck by a comet or meteor large enough to create a huge shockwave felt around the globe. Widespread dust and debris rain down, disrupting the climate and causing extinction on a global, rather than local, scale.
Types of fossils formed in this period