Impact Fractures


This is a Mousterian point of unknown age with a small impact fracture on the tip. Could it be a projectile?   

Standardized experiments with stone-tipped weapons have been applied as a methodological approach in the investigation of prehistoric flint points since the late 1970s. The first experimentally based studies described diagnostic impact fractures (DIF) and con­firmed the function of Upper Paleolithic and Mesolithic points of various types as tips of projectile weapons. Subsequent experiments involved point types characteristic of earlier periods (Mousterian Points, MSA Points) and extended the range of research objectives including such issues as invention of projectile weapons and human evolution.

Producing mechanically projected weaponry (bow and arrow) would imply that people were capable of constructing high-tensile strings and sometimes complex adhesives, both of which involve multi-stage planning and assembling. These technologies may have assisted in niche broadening among modern humans expanding out of Africa after c. 50 k.a. or even earlier (70 k.a. BP; Howiesons Poort industry in South Africa), by providing a flexible technology allowing them to focus more intensely on certain foods while broadening their overall dietary base. At present there are contentious issues around when and where different hunting weapon types appear in the archaeological record. Because organic components of hunting weapons rarely survive over extended periods of time, Archaeologists rely mostly on contextual evidence, such as macro-fracture patterns to interpret prehistoric hunting technologies.

A macro-fracture can be defined as a fracture that is visible with the naked eye or with a hand lens. DIF’s are macro-fractures that have been shown through experiments to be associated with stone artifacts used as weapon tips. The assumption is that these fractures are caused by longitudinal impact during use (e.g. hunting), and that variations of this use will leave different breakage patterns on the tools. The characteristics of impact function, based on macro-fracture analysis,  are considered universal for hunting tools of flint and related raw materials (Fischer et al. 1984).

There are several DIF breakage types, but only step terminating fractures , unifacial spin-off fractures larger than 6 mm, bifacial spin-off fractures and maybe impact burination have been referred to as the primary DIF types to identify the potential use of stone tipped weaponry. These fractures seem to be specific for projectile use, which is substantiated by the fact, that spin-off fractures >6 mm were excessively rare and bifacial spin-off fractures  virtually absent during trampling and knapping experiments. Anyhow the question remains: what would happen, if the suggested projectiles were used for other tasks (grooving, boring…).

Snap, feather, hinge terminating fractures and tip crushing are recorded during macro-fracture analyses to describe the complete range of damage seen on a tool. They may occurre on a stone projectile toll, but unfortunately they are unspecific. Such damage can also result from a variety of other activities (such as trampling and knapping) and should not be used alone as potential indicators of projectile impact (Villa et al., 2009).

Suggested Reading:

Wurz, S. 2007. 70 000-year-old geometric backed tools from the Howiesons Poort at Klasies River, South Africa: were they used for hunting? Southern African Humanities 19: 1–16


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