The Quaternary is the third and current period of the Cenozoic era. Often referred to as the "Age of Humans," the Quaternary began about 2.6 million years ago.
The Quaternary is defined by its periodic episodes of glaciation, which we know as the "ice ages." These episodes of glaciation correlated with drastic changes in climates and sea levels. Land bridges were formed, allowing animals and early humans to migrate across continents. Mammoths and giant sloths roamed the earth before becoming extinct, and Homo sapiens evolved and spread globally, becoming the defining biological force of this current geological chapter.