the form of a tool have underscored the importance of establishing the reasons for the existence of recurring forms before offering explanations for assemblage variation. These studies have shown that many of the tool types described by Bordes actually represent different stages in a sequence of edge modification. Tools become blunted during use, and a resharpening of those blunted edges results in a change in the shape of the tool. Not all of the sixty-three tool types that Bordes had identified represented either culturally determined templates or tools fashioned for a particular task.

Similar changes in the interpretation of Acheulean hand-axes have also been made. In the first half of the twentieth century archaeologists often argued that hand-axes were better made and more refined in later, rather than earlier, time periods. Thus, measures of the degree of two-dimensional symmetry, extent and refinement of retouch, and/or overall shape were used to establish the relative chronology of otherwise undated assemblages from Africa, the Middle East, and Europe. Underlying these schemes was the assumption that the shape of a hand-axe was controlled primarily by the amount and refinement of retouch and thereby provided a measure of the technical sophistication of the toolmaker.

In the late 1970s Peter Jones undertook a series of knapping experiments designed to investigate the effects of the flaking properties and the form of particular raw materials on both the shape and the durability of the working edges of axes recovered from sites at olduvai gorge. He found that the classic teardrop shape of the hand-axe inevitably resulted when an attempt was made to maximize both the length of the cutting edge and the weight of the axe at the same time; in other words, the fundamental determining factor with respect to hand-axe shape was neither style nor the technological proficiency of the knapper. Instead, variations on the teardrop shape of experimental hand-axes were shown to be related to the properties of the raw material and the form of the tool blank from which the axe was fashioned, the quality of the working edge on the finished tool, and the amount of resharpening undertaken on the axe edges.

Studies such as those by Dibble and by Jones, which emphasized raw material properties and resharpening, do not deny the possibility of using stone to obtain information about cultural affiliation, but they do highlight the fact that many variables contribute to the final form of an artifact. Consequently, approaches such as the one developed by Bordes, which makes quite specific assumptions about the reasons why artifacts of different shape exist, have fallen out of favor. In response, many researchers have shifted their attention to other variables affecting artifact form and assemblage composition, especially techniques of artifact manufacture.

Initial studies of the ways in which tools were made were intended to characterize the stone-working techniques of a particular portion of the archaeological record (such as the Acheulean, Middle Paleolithic, or Upper Paleolithic). Most of these studies were based on the experimental replication of forms recovered from archaeological sites, and they provided a basis for outlining the development of stone technologies over time. However, it was soon realized that studies investigating different ways of reducing a waterworn cobble, an Acheulean hand-axe, or a Levallois core had the potential to provide more detailed information about the relationship between stone-working techniques and the composition of artifact assemblages. Investigations into the different techniques that can be used to reduce Middle Paleolithic Levallois cores are a good example (Dibble and Bar-Yosef 1995).

During the 1970s and 1980s studies of artifact resharpening, raw material variability, and manufacturing techniques showed that recurring artifact types result from a complex series of processes and should not be interpreted simply as culturally ordained tool types. As a consequence, discussions about the impact of cultural tradition on artifact assemblages have begun to involve a much more detailed consideration of the concept of style and culture. Some archaeologists have explored the behavioral significance of style in contemporary settings for particular types of artifacts; other researchers have examined the theoretical and methodological problems that arise from attempts to interpret