While it is popularly believed that evolution occurs through mutations in DNA, that's simply not true. Now scientists have more evidence that evolution functions even among proteins that have no DNA.
Infectologists at Scripps Institute discovered this evolutionary behavior by studying the behavior of prions, a type of protein you may know because mutated prions in the brain cause mad cow disease. What the researchers discovered was that when they moved prions from brain cells to a new environment, the proteins changed. The prions best-suited to the new environment were slightly different from those that succeeded in brain cells, and those came to dominate the population. When the prions were moved back to the brain cells, however, the prion population shifted back. According to BBC News:
Charles Weissmann, head of Scripps Florida's department of infectology who led the study, said: "On the face of it, you have exactly the same process of mutation and adaptive change in prions as you see in viruses . . . This means that this pattern of Darwinian evolution appears to be universally active. In viruses, mutation is linked to changes in nucleic acid sequence that leads to resistance. Now, this adaptability has moved one level down- to prions and protein folding - and it's clear that you do not need nucleic acid (DNA or RNA) for the process of evolution."