A new study shows that certain organisms can undergo reverse evolution, that is, go back to the way they were living before evolving new traits. The study challenges the idea that evolution is uni-directional and an organism can't undo changes. The idea that organisms can't revert back is held by Dollo's law, which states "that evolution is not reversible; i.e., structures or functions discarded during the course of evolution do not reappear in a given line of organisms. The hypothesis was first advanced by a historian, Edgar Quinet."The present study was conducted by a research team led by two biologists...