How did Acheulean hand axes change over time?

Acheulean hand axes underwent significant technological evolution over hundreds of thousands of years, transitioning from crude, heavy implements to refined, symmetrical tools.12

Evolution of Technique and Form

• Early Stages: The earliest hand axes, such as those found at Olduvai Gorge, were crude, pointed bifaces. These were created by rapping a stone core against an "anvil" stone, resulting in a thick, heavy tool with a sinuous cutting edge.1
• Intermediate Development: Over time, the use of a hammerstone replaced the anvil, allowing for the flaking of the entire surface. This produced thinner, oval-shaped implements with relatively straight edges.12
• Refinement: In later stages, the hammerstone was replaced by softer materials like bone or wood. These "hammers" allowed for the removal of smaller, flatter flakes, resulting in a smoother, sharper, and more elegant tool.1

By the late Acheulean, hand axes were typically pointed, often featuring a roughly finished butt end. These tools were not hafted but held directly in the hand, serving as versatile implements for hunting, scraping, and chopping. Eventually, these traditions were succeeded by more specialized techniques, such as the Levalloisian method.12