Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Pleistocene
Contents
Overview
Defining and Dating the Pleistocene Boundary
Pleistocene Glacial Events
Pleistocene Ecosystems and Extinctions
Human Evolution during the Pleistocene
Evidence
Skeleton of the woolly mammoth
learn more
sample
Walrus
Saber-toothed cat
Human ancestor
references and links
Foundational Concepts
Dating Methods
Earth Processes
Life Processes
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Pleistocene Ecosystems and Extinctions
Glacial cycles were not the only geological and climatic characteristics of the Pleistocene. Volcanic activity was also occurring in the rift valleys of Africa and in western North and South America. In southwestern North America, the Colorado River began to carve out the Grand Canyon.

Although the Pleistocene represents a brief portion of geologic time, it includes detailed records of profound changes in climate and landscape. Most Pleistocene plants and animals were quite similar to modern forms. Many species of flowering plants, conifers, mosses, insects, mollusks, birds, and mammals still exist today. In many places of the world, the Pleistocene landscape would have looked very similar to that of today. However, glaciation cycles resulted in the evolution of cold-adapted mammals in northern continents, as well as fragmentation and geographic shifts of existing ecosystems. During these periods, familiar organisms were often found in novel environmental combinations.

The Pleistocene was also a time of extinction. By the end of this epoch, many species of mammals had gone extinct in North America, including llamas and camels, tapirs and horses, and musk oxen. In addition, other large mammals such as mammoths and mastodons, saber-tooth cats, and ground sloths went completely extinct. Similar extinctions of large mammals occurred in Australia and South America as well. These extinctions are a source of active research and controversy. Many scientists believe that human migrations were an important factor in the extinctions of large mammals, especially in North America and Australia. However, the dramatic climate changes that were also occurring may have been a factor as well.

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Overview | Defining and Dating the Pleistocene Boundary | Pleistocene Glacial Events
Pleistocene Ecosystems and Extinctions | Human Evolution during the Pleistocene



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