A nearly complete fossil skeleton 3.67 million years old provides new insight into how the hominin ancestors of man used their arms.

Corals are colonies of tiny, genetically identical animals known as polyps that form their characteristic skeletons by combining the mineral calcium carbonate with fibers of living matter, in a process known as biomineralization. But how the skeletons of stony corals arrange scores of different proteins in the process of biomineralization has been largely unknown.