The Pleistocene, lasting from about 2.6 million to 11,700 years ago, was the first of two epochs in the Quaternary period. It's sometimes called the "Ice Age" due to its repeated cycles of glaciation.
At the height of the Pleistocene's glacial periods, ice sheets covered much of North America, Europe, and Asia; sea levels dropped by hundreds of feet, and land bridges formed. The Pleistocene is famous for megafauna — very large animals, such as woolly mammoths, saber-toothed cats, giant ground sloths, and dire wolves — that were adapted to the cold. Alternating cycles of glaciation and warmer, interglacial periods are linked to changes in Earth's orbit. Humans evolved during this time, including Neanderthals and our own species, Homo sapiens.