Michael Hammer, University of Arizona (image) University of Arizona Caption Michael Hammer, shown here with an ancient hominid fossil, is an evolutionary geneticist at the University of Arizona. Credit Michael Hammer Usage Restrictions This visual may only be used in conjunction with reporting/posting of this news release. Image/video credit must be included exactly as indicated. 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.