3 to 1.8 million years ago. It follows the Miocene Epoch and precedes the Pleistocene Epoch of the Quaternary Period. Pliocene environments were generally cooler and drier than those of preceding Tertiary epochs. In general, Pliocene mammals grew larger than those of earlier epochs. The more advanced primates continued to evolve, and it is possible that the australopithecines (see Australopithecus), the first creatures that can be termed human, developed late in the Pliocene