Tollense River (IMAGE) Johannes Gutenberg Universitaet Mainz Caption Archaeologists have been systematically searching a section along the Tollense river for more than 10 years. Credit photo/©: Stefan Sauer/Tollense Valley Project Usage Restrictions This image may only be used in connection with the press release "Lactose tolerance spread throughout Europe in only a few thousand years", issued by Johannes Gutenberg University Mainz on September 3, 2020. 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.