The stone age can be divided into the Paleolithic ("Old Stone Age"), during which all humans were hunter-gatherers; the Mesolithic ("Middle Stone Age"), the transitional phase to agricultural life; and the Neolithic ("New Stone Age"), when humans subsisted through agriculture.
The Paleolithic, which spans over ninety percent of human existence, can be further divided into three parts.
We currently live in an interglacial period, which began ca. About 14 billion years ago, the Big Bang gave birth to a universe containing pockets of dust.
Some of these species migrated out of Africa, settling regions of Eurasia.
All would eventually go extinct, however, leaving the world to be dominated by a single human species: .
The Lower Paleolithic was the age of human evolution.
Various species of (aka "modern behaviour"), which emerged ca. Humans of the Lower and Middle Paleolithic exhibited primitive behaviour; though they could make simple stone tools and eventually came to control fire, these humans did not behave much differently than the rest of the animal kingdom. This animal subsequently evolved to walk upright (rather than on all fours), allowing it to see much farther across the plains.