Thumb Diagram (IMAGE) Cell Press Caption This image diagrams the difference between human and chimpanzee models of thumb muscles, which the researchers used to study the evolution of thumb dexterity. Credit Professor Katerina Harvati, Dr. Alexandros Karakostis, and Dr. Daniel Haeufle Usage Restrictions Credit required. License Licensed 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.