Our bones did not begin deep inside the body. They started in the skin, not long after the first complex animals took shape. Ever since, skin bones have remained a recurring motif in evolution. Yet we ...

Bones did not originally form deep inside the body. They started in the skin soon after the first complex animals took shape. Ever since, ‘skin bones’ have appeared again and again in evolution.

The earliest evidence of skin bones dates back approximately 475 million years. At that time, some of the earliest vertebrates evolved an elaborate bony exoskeleton. This might sound surprising ...