BEHOLD THE FACE OF YOUR DISTANT RELATIVE

A fossilised face stares up through the microscope lens. The bizarre fossil provides scientists with extremely detailed insight into the beginning of 540 million years of human evolution.

540 million years ago

Atiny monster is wriggling between the sand grains. With a large mouth surrounded by wrinkled skin folds, it consumes everything that it can get hold of, forcing the remains out through blunt spikes on the side of its body.

The odd creature’s fossilised remains, which only measure 1 mm, have just been discovered by a team of scientists. The animal has been named Saccorhytus (wrinkled sack), and the discovery sheds much needed light on the first branches of our family tree.

Genetic studies have long shown that humans and all other vertebrates are related to echinoderms such as starfish, sea urchins, and sea cucumbers, but the fossil remains of the common ancestor of humans and sea cucumbers has so far escaped palaeontologists' attention. Saccorhytus fits into this very important spot on the family tree, and the tiny creature helps scientists understand how the founda-tions of the human body were laid.

Like us, Saccorhytus was characterised by midline symmetry. Its thin, flexible skin probably covered muscles and a primitive nervous system, which allowed the animal to wriggle forward on the bed of a shallow sea in what is now China. Moreover, scientists believe that the animal’s spikes could be an initial stage of human branchial arches, which play an important role in embryonic development.