The first epoch of the Quaternary period. It extended from the end of the Pliocene, about 2.58 million years ago, to the beginning of the Holocene (the present epoch), about 11 700 years ago. The Pleistocene is often known as the Ice Age as it was characterized by a series of glacials, in which ice margins advanced towards the equator, separated by interglacials when the ice retreated. See also ice age.