Birth simulation of Lucy (IMAGE) University of Zurich Caption Birth simulation of Lucy (Australopithecus afarensis) with three different fetal head sizes. Only a brain size of maximum 30 percent of the adult size (right) fits through the birth canal. Credit (Picture: Martin Häusler, UZH) Usage Restrictions none License Original 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.