How did vertebrates first evolve jaws?

A zebrafish showing the skeleton and jaw (magenta), the eye (green circle on the left), and gill-like pseudobranch and gills (green structures on the right). (Image by Mathi Thiruppathy/Crump Lab)

Five-hundred million years ago, it was relatively safe to go back in the water. That’s because creatures of the deep had not yet evolved jaws. In a new pair of studies in eLife and Development, scientists reveal clues about the origin of this thrilling evolutionary innovation in vertebrates.

In the studies, Mathi Thiruppathy from Gage Crump’s laboratory at USC, and collaborator J. Andrew Gillis from the University of Cambridge and the Marine Biological Laboratory, looked to embryonic development as way to gain insight into evolution—an approach known as “evo-devo.”