The Holocene is the time period on Earth that started about 12,000 years ago and is still happening today. During the Holocene, some animals and plants have died out or become extinct – that means that they no longer exist in the world. The timeline of extinctions in the Holocene is the list of different animals and plants that have become extinct or have died out during this time. It helps us to understand what kinds of animals and plants have died out, when they disappeared, and why they disappeared. Some of the species that have become extinct or have died out during the Holocene are the dodo bird, the western black rhinoceros, some types of large whales, and the American lion. People have caused these extinctions by hunting animals, destroying their habitats, or introducing alien species or diseases.