Thermal engineering of stone increased prehistoric toolmaking skill

Area of Science:

• Archaeology
• Materials Science
• Lithic Technology

Background:

• Intentional heat treatment of toolstone is an ancient practice dating back at least 70,000 years BP.
• The precise benefits of heat treating toolstone remain a subject of debate among researchers.
• Two primary hypotheses exist: reduced flake propagation force versus altered flake morphology.

Purpose of the Study:

• To systematically investigate the effects of heat treatment on toolstone.
• To test whether heat treatment primarily reduces the force required for flake propagation or also alters flake morphology.
• To provide empirical data to resolve the long-standing debate on the advantages of heat treating toolstone.

Main Methods:

• Toolstone cores were subjected to three temperature conditions: ambient, 300°C, and 350°C.
• Automated propagation procedures were used to generate flakes, minimizing human variability.
• Flake morphology was quantitatively analyzed using nine distinct measures.

Main Results:

• Heat treatment was confirmed to significantly reduce the force magnitude required for flake propagation.
• No significant or systematic differences in flake morphology were observed across the three temperature treatment groups.
• Analysis of nine morphological measures showed no discernible impact of heat treatment on flake form.

Conclusions:

• Heat treatment demonstrably lowers the force threshold for creating stone flakes.
• The study's findings indicate that heat treatment does not significantly alter the major morphological characteristics of stone flakes.
• This research challenges the notion that heat treatment fundamentally changes flake form, suggesting its primary effect is on the mechanics of fracture.