The Neogene is a geologic period and system in the International Commission on Stratigraphy (ICS) Geologic Timescale starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago. The Neogene Period follows the Paleogene Period as the 2nd period within the Cenozoic Era and is succeeded by the Quaternary Period. The last epoch into which the Paleogene Period is subdivided is the Oligocene Epoch. The Neogene Period is subdivided into 2 epochs, the earlier Miocene Epoch and its succeeding Pliocene Epoch. The first epoch into which the Quaternary Period is subdivided is its Pleistocene Epoch. The Neogene covers roughly 23 million years. During the Neogene mammals and birds evolved considerably. Most other forms were relatively unchanged. Some continental motion took place, the most significant event being the connection of North and South America in the late Pliocene. Climates cooled somewhat over the duration of the Neogene culminating in continental glaciations in the Quaternary Period that follows, and that saw the dawn of the genus Homo.