The Stone Age (known to scholars as the Paleolithic era) in human prehistory is the name given to the period between about 2.5 million and 20,000 years ago. It begins with the earliest human-like behaviors of crude stone tool manufacture, and ends with fully modern human hunting and gathering societies. The Paleolithic is the earliest archaeology; anything older is paleontology. Today scholars divide the Paleolithic into three categories, more or less as follows.
Lower Paleolithic (sometimes called the Early Stone Age)
The Lower Paleolithic lasted between 2.5 million-200,000 years ago (or at least according to one permutation), and it was when the Hominin ancestors of human beings, including Australopithecus, Homo habilis, Homo erectus and Homo ergaster, roamed most of the earth and began making the first stone tools.
See the Guide to the Lower Paleolithic for sites and details.
Middle Paleolithic (Middle Stone Age)
The Middle Paleolithic (ca 200,000 to 45,000 years ago) witnessed the evolution of Neanderthals and the first anatomically modern Homo sapiens sapiens, and some of the first glimmers of modern behaviors: sophisticated stone tools, caring for the elderly, hunting and gathering and some amount of symbolic or ritual behavior.
See the Guide to the Middle Paleolithic for specific sites and more information.
Upper Paleolithic (Late Stone Age)
By the Upper Paleolithic (45,000-10,000 years ago), the Neanderthals were in decline, and by 30,000 BP, they were gone. Modern humans spread all over the planet. The LSA is characterized by fully modern behaviors such as cave art, hunting, and making a wide range of tools in stone, bone, ivory and antler.
See the Guide to the Upper Paleolithic for specific sites and more information.