A tool making industry that first appeared about 1.5 million years ago in East-Central Africa. This particular kind of tool making is most often associated with Homo ergaster and western Homo erectus. These tools are characterized by numerous varieties of oval, pointed, and cleaver-edged hand axes and were often produced from quartzite, glassy lava, chert and flint.
The tools of this industry are more specialized and skillfully crafted than those of the Oldowan (providing four times the cutting edge). Acheulean tools are characterized by two main innovations. First, the working of the entire stone into a useful shape rather than chipping flakes off of one side to make a cutting edge, and second, the shaping of the stone on both sides to produce a symmetrical (bifacial) cutting edge.
Rather than only flaking large chips off of the core itself, these tools were produced with careful, smaller flaking of the already shaped core. This allowed for a more refined shape in a larger tool. The making of these tools required both an understanding of the concept of symmetry and the ability to have a clear mental image of the tool before production.
Around one million years ago, the teardrop shaped hand axes appeared, and by 500,000 years ago the Acheulean industry had spread to Europe (with Homo heidelbergensis), the Near East and India. It never spread to Asia, where Homo erectus continued using Oldowan tools until the species’ extinction. These tools were utilized until about 200,000 years ago.
It is interesting to note that the production of these tools is seen by some as a large step in the direction of modern human intelligence because of the capacity for imagination that was required. Unlike tools which came before that were shaped from stones that began as tool-shaped (oval and hand sized), Acheulean tools were shaped from stones that did not resemble the tool they would become. This indicates a high level of forethought on the part of the tool-makers.
Information flaked off of:
http://www.handprint.com/LS/ANC/stones.html
http://anthroclass.com/lectures/lbanth313/class5.html
http://www.massey.ac.nz/~alock/virtual/lockfin.htm