Phanerozoic
Quaternary Period

The Quaternary spans from 2.58 million years ago to present day, and is the shortest geological period in the Phanerozoic Eon. It features modern animals, and dramatic changes in the climate. It is divided into two epochs: the Pleistocene and the Holocene.

The Pleistocene lasted from 2.58 million to 11,700 years ago. This epoch was marked by a series of glacial periods (ice ages) as a result of the cooling trend that started in the mid-Eocene. There were numerous separate glaciation periods marked by the advance of ice caps as far south as 40 degrees N latitude in mountainous areas. Meanwhile, Africa experienced a trend of desiccation which resulted in the creation of the Sahara, Namib and Kalahari deserts. Mammoths, giant ground sloths, dire wolves, sabre-toothed cats and archaic humans such as Homo erectus were common and widespread during the Pleistocene. A more anatomically modern human, Homo sapiens, began migrating out of East Africa in at least two waves, the first being as early as 270,000 years ago. After a supervolcano eruption in Sumatra 74,000 years ago caused a global population bottleneck of humans, a second wave of Homo sapiens migration successfully repopulated every continents except Antarctica. As the Pleistocene drew to a close, a major extinction wiped out much of the world's megafauna, including non- Homo sapiens human species such as Homo neanderthalensis and Homo floresiensis. All the continents were affected, but Africa was impacted to a lesser extent and retained many large animals such as elephants, rhinoceros and hippopotamus. The extent to which Homo sapiens were involved in this megafaunal extinction is debated.

The Holocene began 11,700 years ago at the end of Younger Dryas and lasts until the present day. All recorded history and so-called " human history " lies within the boundaries of the Holocene epoch. Human activity is blamed for an ongoing mass extinction that began roughly 10,000 years ago, though the species becoming extinct have only been recorded since the Industrial Revolution. This is sometimes referred to as the " Sixth Extinction " with hundreds of species gone extinct due to human activities such as overhunting, habitat destruction and introduction of invasive species.
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