Knives were crafted to cut. Yet how many of us use them to slit an envelope. Or prise open a lid. Nature too has its ways of perverting a design so that its initial role is altered to become another. This is exactly what happened to a protein known as osteocrin. Osteocrin was first discovered in bone. Though it remains unclear how it works in detail, it seems to influence longitudinal bone growth. Almost a decade later, scientists found out that osteocrin is also expressed in the primate brain where data suggest a role in neuron growth. This may not come as a surprise - here is a protein that promotes growth both in bones and in the brain. What is intriguing, however, is that it seems to drive neuron growth in the anthropoid primate only, whereas its role in bone growth, for instance, is shared by many other species too. Osteocrin has acquired this new explicitly-primate skill following a series of mutations which changed the way it is expressed. Would this imply, then, that it is partially responsible for intelligence? More