The Quaternary Period /kwəˈtɜrnəri/ is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present. Traditionally it was preceded by Tertiary which is no longer recognized as a formal geological unit but is still in colloquial use.This relatively short geological period is characterized by a series of glaciations and by the appearance and expansion of anatomically modern humans. Also of note, all objects that are suitable for carbon dating are enclosed in this period. The Quaternary includes two geologic epochs: the Pleistocene and Holocene.