Simon de Graaf and Dr. Jessica Rickard, University of Sydney (image) University of Sydney Share Print E-Mail Caption Researchers who thawed 50 year old sheep semen and successfully impregnated 34 ewes Associate Professor Simon de Graaf and Dr. Jessica Rickard. Pictured here with the healthy progeny from the semen. Credit Morgan Hancock/University of Sydney Usage Restrictions For this story only Share Print E-Mail 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.