Two Growth Lines (IMAGE) Uppsala University Caption The Low growth and High growth lines are two of the populations included in the study. These lines were developed by Paul Siegel at Virginia Tech from a common ancestral population. They show an almost ten-fold difference in body weight at eight weeks of age after 40 generations of selections for low or high growth, respectively. A dramatic illustration how selection can alter phenotypes. Credit Uppsala University Usage Restrictions None 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.