The paper mulberry evolved its uniquely fibrous inner bark around 31 million years ago, long before the woody tree was first used for bookmaking during China’s Tang dynasty. This adaptation, which makes the nutrient-rich plant easy to pass through foraging animals, may have been its way of feeding nearby soil microbes. Botanists in China discovered this connection in the first analysis of the Broussonetia papyrifera genome, published February 26 in the journal Molecular Plant.