Figure 3 (IMAGE) Nagoya University Caption Investigation of mechanical properties of rocks suggested that paleolithic humans changed their choice of raw material to suit their stone tool morphologies and production techniques. Credit Eiki Suga (photos), Reiko Matsushita (illustration and design) Usage Restrictions Credit must be given where image is used License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.