Human ancestors have been using stone and other tools since long before the emergence of Homo sapiensapproximately 200,000 years ago.^[22] The earliest methods of stone tool making, known as the Oldowan "industry", date back to at least 2.3 million years ago,^[23] with the earliest direct evidence of tool usage found in Ethiopia within theGreat Rift Valley, dating back to 2.5 million years ago.^[24] This era of stone tool use is called the Paleolithic, or "Old stone age", and spans all of human history up to the development of agriculture approximately 12,000 years ago.

To make a stone tool, a "core" of hard stone with specific flaking properties (such as flint) was struck with ahammerstone. This flaking produced a sharp edge on the core stone as well as on the flakes, either of which could be used as tools, primarily in the form of choppers or scrapers.^[25] These tools greatly aided the early humans in theirhunter-gatherer lifestyle to perform a variety of tasks including butchering carcasses (and breaking bones to get at themarrow); chopping wood; cracking open nuts; skinning an animal for its hide; and even forming other tools out of softer materials such as bone and wood.^[26]

The earliest stone tools were crude, being little more than a fractured rock. In the Acheulian era, beginning approximately 1.65 million years ago, methods of working these stone into specific shapes, such as hand axesemerged. The Middle Paleolithic, approximately 300,000 years ago, saw the introduction of the prepared-core technique, where multiple blades could be rapidly formed from a single core stone.^[25] The Upper Paleolithic, beginning approximately 40,000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely.^[27]