What if you had to wear a huge backpack all the time? Quick, agile movements would become much more difficult, and you'd probably get tired pretty fast. Maybe you would downsize the items in your pack to fit into your pockets. Or you might change your way of life and get rid of material possessions altogether. These were the issues that ancient ancestors of the squid faced when they began to free themselves from life on the seafloor 400 million years ago. Abundant fossils of preserved hard parts give clues to what these ancestors probably looked like: Imagine a modern squid curled up and stuffed into a cumbersome shell, limited to crawling on the seafloor. But with all that bulk on their backs, scientists still puzzled over how the ancient animals might have moved. Direct observation of extinct animals is impossible, but recent fossil finds of soft body parts may provide an answer.