Prehistoric stone tools were used throughout the Paleolithic (Old Stone Age), which characterizes the period. The Paleolithic extends from 2.5 million years ago (mya), when the ancestors of Homo sapiens (early homonids, i.e. Homo habilis) first started using stone tools and continues until the establishment of agriculture at about 10,000 BCE.
The Paleolithic is broken down into the Lower Paleolithic, Middle Paleolithic, and Upper Paleolithic based on cultural trends, including tool complexity. The Lower Paleolithic is from 2.5 mya to about 120,000 years ago, the Middle Paleolithic is between about 300,000 years ago until 30,000 years ago, and the Upper Paleolithic is from 40,000 to 10,000 years ago.
The ending and starting dates for the eras do not match because people in different areas of the world made the cultural transitions at different times. The Paleolithic is followed by the Mesolithic and Neolithic, meaning Middle and New Stone Age. The Stone Age is then followed by the Bronze Age.
Different stone tool industries are divided into four "modes" based on their sophistication. The first is Mode 1, which the most famous example of which is the Olduwan tool industry, and lasted from 2.5 mya to about .25 mya. Another tool industry in this category was the Clactonian, which came much later (around 300,000), but was simplistic for the time, used by Homo erectus rather than modern humans.
Mode 1 tools are simple choppers and flake-based tools such as scrapers, cleavers, and primitive awls. They were made out of any stone that could retain an edge, were "unretouched" (edges made by a few big smacks, no huge effort to make them very sharp or straight), and relatively simplistic, usually only with one worked edge (unifacial). When found in Europe, Olduwan tools used to be called Abbevillian, and only Olduwan when found in Africa, but the Olduwan name has now been adopted for both.
Mode 2 stone tools are part of the Acheulian tool industries, probably the most famous of stone tool industries due to their combination of age and relative sophistication. These are the bifacial hand axes, considered a critical division between the older stone tools and newer stone tools. Broadly, Mode 2 tools were used from about 1.65 mya to 100,000 years ago. It was Acheulian tool users that originally left Africa and colonized Europe about 1.5 mya.
Acheulian tools are distinct because it was the cores themselves which were prized, rather than the flakes knocked off the core. Soft hammers made from wood and bone were used to achieve greater control over the end product. Acheulian tools took more effort to make and were probably used for longer periods, possibly being among the first true "human possessions." A city person thrown into an environment in which he was forced to use stone tools might think of making Mode 2 stone tools right away.
Mode 3 stone tools are characterized by being produced via the Levallois technique, which involved flaking a central core just to produce a regularly-shaped "Levallois core" which was then carefully broken to produce a "Levallois point" - a range of sharp and regular stone tools that look almost as if they were made by machines rather than a man. Short lithic blades were produced. Mode 3 tools are most prominently associated with the Neanderthal Mousterian tool industry in the Middle Paleolithic.
Mode 4 stone tools are grainy rocks such as basalt, and are produced by a grounding process with the help of water to make arbitrary shapes. The stone furniture found in The Flintstones would have required Mode 4 technology to be created. This mode of tool creation was adopted just a bit before the arrival of modern history, primarily found at Neolithic sites, which existed from the advent of agriculture 10,000 years ago until the Bronze Age, which began roughly 3,500 years ago.
