Hierarchies in Biomineral Structures

From sea urchin teeth to mammalian bones, the skeletons of organisms often contain several levels of structural hierarchy, designed to resist mechanical damage. In his Perspective, Currey describes several such hierarchical systems, highlighting in particular the high level of hierarchical organization in the skeleton of the deepwater sponge Euplectella (described by Aizenberg et al.). The complex structure of biomineralized systems probably serves mostly to avoid the traveling of cracks through the structure; Currey suggests that the chemistry of the mineral used in a skeleton is much less important than how this mineral is arranged in space.