a1 Department of Materials Science and Engineering, University of California, Berkeley, CA 94720
a2 Museum of Paleontology, University of California, Berkeley, CA 94720
Bone is an important material in many scientific disciplines because of its unique structure-property relationships, which are intrinsically dependent on its nanoscale components, bioapatite and collagen. As a living tissue, bone has evolved over hundreds of millions of years, and most vertebrates are now extinct. However, the vast majority of the relevant literature has engaged only modern bone tissues, neglecting the deep time perspective. Why?