Résumé
Teeth and bones are fundamental features of vertebrate organisms. The earliest vertebrates date from fossils that are over 500 million years old and existed at the time of the Cambrian Explosion, a great burst of innovation in the evolutionary history. The first creatures with tissues similar to our teeth and bones aren’t seen until tens of millions of years later. Some of these reports have been controversial because challenges imaging the fossils and comparing the tissues between fossil and living forms. New imaging technologies have transformed our ability to study this issue. Studies from multiple laboratories have revealed that tissues equivalent to our teeth and bones originally evolved outside the body—in the bony exoskeletons of our jawless fish ancestors. Inside this exoskeletal armor are small structures that are distinctly toothlike. Detailed comparisons of these features among living and fossil vertebrates and invertebrates reveal that the earliest teeth likely had a sensory function in the external tissues of these fish. Assessing diverse fossil fish reveals that many distinct features of our bones and teeth, such as the capacity to remodel, originally came about in jawless fish.
