During the Earth’s history there were many ice- ages, and the last one lasted between 70,000 to 10,000 years ago. During that period many of the today’s animals had their huge versions, which looked more or less the same, but they often had a different anatomy. One of such examples is a giant beaver, which lived in North America and got extinct 10,000 years ago. Unlike today’s beavers the giant beaver had an extra cavity in its head, spreading from the front to the back of their skull. After examining giant beaver’s skull, using CT scan (X-ray images taken from many different sides of an object to create a 3-D image) scientists came to the conclusion that this special cavity’s purpose was to produce sound in order to provide a way of communication between the beavers. One of the scientists blew a note in the cavity and described the sound as a bleating, although the exact sound cannot be produced because the soft tissues were missing. Scientist said that this type of skull cavity is unique to giant beavers.