With any luck, humans change a lot over the course of our time on Earth. As we grow out of our teeny onesies and our teenage styles, the aging process can feel a lot like shedding a past self. But other creatures literally do that: step out of their bodies and grow into a new one. For trilobites—marine arthropods that appeared in the Cambrian period, more than 500 million years ago—molting was a key part of growing up. Trilobites could crawl out of their exoskeletons more than two dozen times…
