Researchers from the Max Planck Institute for Psycholinguistics in Nijmegen, the Free University of Brussels (VUB), and Sealcentre Pieterburen studied seal pups of only a few weeks old. The pups lowered the pitch of their voice when they heard louder noises. This vocal flexibility makes seals an excellent animal model for studying the evolution of human speech, according to an article published on the Max Planck website.