An endangered monkey has given scientists new insights into evolution. The leaf-eating douc langur, native to East and Southeast Asia, has a quot;duplicatedquot; gene that started as an extra copy of a gene for a particular enzyme but mutated into a gene for another enzyme with a different purpose. By recreating the gene's path from one enzyme to the other, scientists have addressed an important debate over how natural selection shapes such duplications. Throughout evolutionary history, extra copies of genes have popped up spontaneously in the genomes of many organisms. This gene duplication is thought to be a major source...