Three years ago, I wrote a series of blog posts about how scientists at the University of Oregon reconstructed the 450-million-year history of a protein. You can read the posts here, here, and here. What was particularly elegant about the study was how the scientists recreated the ancestral protein as it existed over 400 million years ago, to see how it functioned. Then they  pinpointed the mutations that transformed the protein, shifting it from an old function to a new one.

Recently, the scientists tried to run their experiment backwards. They tried to turn the new protein back into the old one. And they failed. In that failure, they’ve discovered something important. They argue that when it comes