Proterozoic

The Proterozoic ( /ˌproʊtərɵˈzoʊ.ɨk/) is a geological eon representing the time just before the proliferation of complex life on Earth. The name Proterozoic comes from Greek and means "earlier life". The Proterozoic Eon extended from 2,500 Ma to 542.0±1.0 Ma (million years ago), and is the most recent part of the informally named "Precambrian" time. It is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic.