Cosmic Impact, Mastodons (image) Dartmouth College Caption An artist's rendition of mastodons, camels and a ground sloth before the environmental changes of the Younger Dryas led to their extinction. Credit Barry Roal Carlsen, University of Wisconsin Usage Restrictions The artist must be credited. 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.