Hammond and Mavuso in field (IMAGE) American Museum of Natural History Caption University of Witwatersrand geologist Silindokuhle Mavuso (left) and study lead author Ashley Hammond at the East Turkana site in Kenya Credit A. Hammond/© AMNH Usage Restrictions Can be used with appropriate credit 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.