An article published in the journal “Nature” describes the study of traces left by organisms that lived over half a billion years ago that could be important to understand how animals evolved. A team of researchers discovered fossil traces of tracks and burrows left by some of the first organisms capable of active movements. Those creatures were very small, with a thickness comparable to that of a hair that could range from 40 to 300 micrometres, but among them there could be the ancestors of most animals.